MCAT General Biology Rapid Review (Part 1)

we are live welcome back it is a cold cold January evening in New York best city on earth trust me I've

been to plenty I've been to Dubai I've been to Abu Dhabi I've been to La been to London I've been to Shanghai nothing quite like New

York all right today we are going to do some biology rapid review we've got a room of just a few people more people will trickle in which is why we're doing

a little bit of review before other people get here and we go over sort of higher yield Concepts more important things that we have to do in our lecture um please come join us if you can if you're in the

area so first thing we're going to talk about is very very very simple what is a

zygote what is a zygote at what point do we refer to something as a zygote

H immediately after fertilization so a zygote is a fertilized egg it is one cell and it begins dividing but we start calling it a zyo

the moment it is one full cell what do I mean by a full cell well here is an egg cell and it's mitochondria right because remember sperm don't have mitochondria

how do sperm get around do you guys remember how sperm travel so there's a flagella inside the tail and we need energy to do that where does it derive its energy from if it

doesn't have a mitochondria seminol fluid is full of fructose why

fructose eny it is energy but why not glucose what's special about fructose it's broken down easier

mhm when you're at the gym sometimes if you get super into gym culture like I was at some point people will tell you if you need a

quick burst of energy drink what sugar orange juice apple juice drink juice right why is

that well it's because if you look at gsis so glucose turns into what what is this on the right this is glucose we threw a

phosphate on the six position so that's glucose 6 phosphate right then that turns into what is

this fructose 6 phosphate and then this is fructose 16 bis phosphate and this is going to turn into dhap and

GAP so that's glucose metabolism right glucose g6p f6p F2

F16 BP p and whatever we've seen that 100 times right that's glucose metabolism interestingly enough fructose metabolism is

different which you don't need to know but I want you to know the basis of why sperm use fructose to move around why fructose is sometimes used in parts of

your body when you need rapid energy fructose can be acted upon by an enzyme

fructokinase to make fructose one phosphate and that fructose one phosphate can be broken down into two things by an enzyme

aldolase b aldas b because this is aldolase right this is aldel this reversible process

this is aldel B Al's cousin right and it will turn this into Gap and dihydroxy acetone

right or sorry my bad deap and glycer alahh because the fruit the phosphates at the top right and we know this top half turns into deap this bottom half

turns into glycer alide phosphate but there's no phosphate on the bottom there's no phosphate on the six position we have to put it on there so then deap will go into glycolysis and the glycer alide will later be turned into glycer

alide phosphate why is this faster than that not necessarily what determines the rate of a reaction it is the rate limiting step what's the rate limiting

step here in glycolysis pfk1 correct this is the rate limiting step of glycolysis do you see

how fructose metabolism evades that step it skips the rate limiting step of glycolysis

fructose metabolism of straight fructose skips the rate limiting step of glycolysis so it is

faster so when sperm are traveling around through what through 7even up

right which is the SEO seino iCal and then or sorry the whatever and the epidemis the vas defin the ejaculatory duct the urethra the penis right seven

up and then the end is nothing right when they're traveling through the seven up and even inside of the body of you know the female inside of the vagina

inside of the cervix inside of the uterus they're surrounded by a fructose they can get around right that's why

now I drew something here on the left I drew a sperm cell and an egg cell right right before fertilization I want you guys to tell me some facts about these two cells things

that you know just off the top of your head which one's bigger egg the egg the egg is way bigger I believe it's the largest human

cell there is I I think you can if if you isolated it you could see one with a naked eye don't quote me on that though that might be a lie I think that's right I

I've heard that before so it's bigger right it also contains like almost everything that goes into the zygote

right but it contains half the DNA it contains 23 n and this contains

23 n and when they come together they make 23 2

N what does 23 2 n mean one pair of every chromosome because if you say two sets then it's one chromosome another chromosome and

that's it this is one pair of 23 chromosomes and are they single or double stranded at this point they're still single stranded and once you start to do

mitosis the beginning of mitosis this is going to become 46 right instead of 23 2N he going to

become 46 2N in reality 92 what do I mean by that let's dumb this down into a very basic level let's say we have an or ISM that only has two

chromosomes David nice to see you again this one's from Mom and this one's from Dad all of the genetic information of

this organism is coded in two chromosomes this is one 2 N CH one chromed when this thing wants to undergo

mitosis right this is 2 2 N if I'm incorrect please quote me because this is even confusing to me I

read it a bit ago to teach to you yes good all right

so there's that now I want you guys to look at this pedigree for me real quick squares mean what in circles mean

what M squares male Circle female and this means affected correct please tell me the inheritance pattern incorrect oh sorry I messed up these

people are not affected I messed up now tell me the inheritance pattern it is not XL if it

exlink where would it be more prevalent in the men correct do you want me to draw you one more generation let's say we kill this person

these people had no kids doesn't matter they're not affected anyways it's a square pretend it's a square it's going to bother

me what is the inheritance pattern this is called m mitochondrial

inheritance mitochondrial inheritance now knowing that it's called mitochondrial inheritance explain the inheritance

pattern comes from the mother every single time a mother has it she gives it to all of her children mother has it all of the children mother has it all of the

children why because the mitochondria comes from the egg cell every single mitochondria on

this planet at some point came from one person about called mitochondria yep

every single human being shares every single human being shares a mitochondria derived of the same person's mitochondria not even derived

mitochondria replicate independently so it's still that same person's mitochondria and if you think about it how many mitochondria does a person have

hundreds of millions maybe billions ridiculous it's crazy to think about this is called mitochondrial inheritance speaking of pedigrees what are some important rules that you should

know about pedigrees so number one is if a mother gives it to all her children it's possible that it is mitochondrial check

other mothers and affected fathers to see if they're not passing it on number two XL disorders specifically x-link recessive disorders will affect men

predominantly what's a good example of that who's a good example of that me I'm a good example of that because I'm color blind and I got color blindness from my mom who got the X trait from her

dad a Al dominant diseases how do we find those out well let's take a step back and let's look at a punet square right so let's say we have two

parents who can name me autosomal dominant disease do you guys know you read it out of my book today Huntington is an autosomal dominant

disease let's say that this person has Huntington and they have sex and have children with someone who doesn't have Huntington

there is a 50% chance that their kid comes out with Huntington and then if their kid with Huntington goes out and has CH children with another person without Huntington

there's a 50% chance of that person having Huntington so you'll see through the chain of people who have the disease 50% of their children have the disease that's how you identify an all

disal dominant disease and why did I why is the big letter the disease dominant if it's dominant the big letter is the disease do you know what the gene is

that's messed up in Huntington's it's called the Huntington Gene but ironically Huntington's disease is spelled like

this but the Huntington Gene is spelled like that this is also a really good example of a

TR nucleotide repeat disorder inside the DNA of the people with Huntington there is a specific region where there are repeats of a

specific sequence so it's DNA DNA DNA and you get this part CAG CAG c a g c a g and if that repetition becomes too

long you got huntingtons and the funny thing is I don't know if this is on the MCAT it might be in a passage or something like that they diseases like these exhibit what's called anticipation anyone know

what anticipation is it gets worse from generation to generation because those repeats get more and more and more so if your mom

has huntingtons God forbid and she has 40 repeats when she passes it on to you you're going to have 50 and the LAN of the repeats corresponds to the severity of

disease so it's very common that in neurology when you study Neurology in medical school you're going to see a family that runs an autosomal dominant disease and the grandfather got it at 70

and then the mother developed at at 50 and the kid comes in at 37 into your office with the same symptoms and that is a textbook definition of

anticipation good very cool we also call this in in like our joking manner we call this KAG KAG KAG disease to

remember that it's a trucy expansion all right so where how did we get here where where are we coming from we're coming from the fact that the egg has the mitochondria right and it passes

it on to the zygote when does the zygote eventually become you know not a zygote it's debated I think it's like eight I think eight is when you start

calling other things cuz then it's like a morula and then a blastula and gastrula and blah blah blah when is it a fetus I believe so I think so these are

all like really shady indeterminate terms but know that there are certain terms you need to know that I don't need to know that I need to eventually know for step probably but I don't know right

now morula gastrula blastula fetus embryo blah blah blah embryo is pretty much like the whole time right but sometimes people don't like referring to fetuses as embryos and I'm not going to touch that discuss

question okay why did I bring this up I wanted to ask you guys right let's say that these

this sperm and egg they make a zygote and then that zygote

splits into two A and B these are twins right these are twins because they split and then they independently grow

so this one independently grows and this one independently grows these are called twins what type of twins are these identical also known as medically what's the

term monozygotic they come from one zygote mono zygotic which means fraternal

twins the other type of twins are known as what dizygotic twins and you will often see whenever they're talking about twins you will often see

them referred to as monozygotic and dizygotic twins very cool by the way since we were talking about the sperm cell and how it

moves around what is the specific cellular protein or cellular component that allows a fella to

move it's part of the cytoskeleton for a hint microtubules yeah microtubules are the important part of fella that let them move very

cool one down one two three four five six seven eight nine 10 11 to go a good question is usually about experimenting with twin twin experiments

twin twin studies those are normally in the psych section though yeah normally the psych section has twin stuff on twin studies

what is this a blood pressure what is this systolic blood

pressure what is this diastolic blood pressure what do either of them mean dub dub right so it's it's the pressure at the highest pressure of the

cardiac cycle and and then the lowest pressure of the cardiac cycle now is this what we mean by you know like does is it 80 throughout the body no because we know that at certain points the blood

almost stops there's almost stasis of blood at certain points of the the vasculature we're talking specifically as part of the heart because the heart is a muscular chamber it is pumping

right everything like this now what are some things that we know well first of all since we're talking about blood pressure we have to get it out of the way BP equals

what cardiac output times systemic vascular resistance systemic vascular resistance right and then this is the one that

everyone knows cardiac output equals what heart rate times volume stroke volume systemic vascular resistance the

natural resistance that your BL blood vessels have to blood flow now last time in a video I haven't uploaded yet I equated these Concepts to

other equations that my physics minded people would remember what were those equations so Bal Co * svr is a lot

like V equal ir and coal HR * SV is a lot like I Q over T take a second to think about

that give me one second okay another question just throwing stuff out there where do we spend more of our time

systolic or diastolic hm diastolic systolic Malcolm diastolic we spend more of our

time diastolic about two-thirds of it because if we spent more of our time in systolic you'd probably feel your heart gasping for breath

right okay good it's basically all you have to know about cine diine when you get to medical school this becomes much more

complicated now remember I want to ask you guys one thing about this equation right here we know that cardiac output is part

of blood pressure correct and we said that stroke volume is part of cardiac output now what's part of stroke volume total body water right because the more water that you have inside the body

the more blood you have inside the vessels which means the more stroke volume you have because you have to push that amount of blood through the body at the same rate which means your heart

fills with more water right remember that thing I told you guys to do way back when I think this is like chapter 3 four of Bio told you guys to hold your hands together like this and just

generate pressure between them right and you you can't do it you like you you can't generate pressure in the middle of that hole because why CU there's nothing

there to create pressure against you need something in between your hands to create pressure against but if I take this water bottle and I put it between my hands now all of a sudden I can

create pressure against this and if the tech that the top wasn't here this would be abely bursting with water that's what your heart does the top is open or it

generates enough pressure to open the top and the blood goes flowing out the top of the chamber right so you see two ways in which the

heart can increase pressure number one it can increase pressure just by pumping harder right which is contractility which is part of the sympathetic nervous system sympathetic nervous system inates

the heart right and allows her increase contractility the other thing is to increase the amount of stuff it pushes against if you increase the amount of

blood inside of the heart chamber you can increase the pressure it generates right and how do we do

that you guys know all about the renin Angiotensin aldosterone system and ADH anti-diuretic hormone which serves

to conserve water increasing the blood volume and blood pressure the RAS is more about blood pressure than it is anything else and

ADH is more about controlling blood what osmolarity because the things that signal for ADH release are sensitive to

blood osmolarity when blood osmolarity gets too high ADH is released aquaporins are sequestered into the collecting duct and D convoluted tubal of the Nephron

and that increases water reabsorption and retention it's how we regulate our sodium balance what else is going to happen

when your blood osmolarity is too high you're going to feel thirsty you're going get thirsty very good

what is this the bicarbonate buffer system very good and it buffers the blood at a lower pH range because the pka here is

what 6.2 6.2 well remember we're still in buffering range because we're within 1.5 of the regular body pH what is the

regular body pH 7.4 7.4 so the majority of this is what Associated or

dissociated the majority is dissociated remember higher P higher pH that way lower pH that way

right there is an enzyme here called does anyone know what it's called the enzyme that does this

Carbonic Carbonic what and hydr Carbonic and hydr now

Sarah who will be here later was so kind enough to share with me a question that she saw and the question was if you inhibit

this enzyme what's going to happen that enzyme specifically inhibit it in red blood

cells inhibit the Carbonic and hydrates in red blood cells what's going to happen h Kira how you

doing so if you inhibit Carbonic and hydr in red blood C could you sit there here in the front could you just

move move that over for him CU he finds it quite difficult to read my handwriting sometimes if you inhibit Carbonic and hydr in red blood cells which of the

following will happen a multiple multiple or just one just one well let's think about it logistically this one is clearly wrong

because if you inhibit the enzyme that makes it you're not going to push it forward that's not going to happen clearly wrong that's what you want to do with the MCAT look at stuff that is blatantly obviously wrong and

immediately get rid of it there are too many times that students look at questions on the MCAT and say oh well you know like if this were the case and this was this maybe that'd be correct no

if you have to jump through Loops of fire to get to an answer it is incorrect that's true of everything in life especially

relationships do not do Leaps and Bounds to make things work decrease oxygen Affinity well we have to think about what decreases and increases oxygen Affinity right we need

to actually actively think about that so that's not blatantly obvious to us yet increase CO2 in tissues well I don't really know without thinking about it what rbcs do for CO2

and tissues yet so let's come back to that as well an increased HC hc3 minus in rbc's well we just said this isn't going to go up so if that doesn't go up that's not going to go up if anything

it's going to go down we're between two choices so now like many times we have a 50/50 shot of guessing right so if you're short on time you just bought yourself a 50-50

chance of getting this right instead of one and four right but we're not short for time because I could be here all night

we'll figure it out okay so the decrease oxygen Affinity right what do we mean by oxygen

Affinity ah you remember this you remember this and there were things that shifted to the right and there were things Sarah we're

talking about your question and there were things that shifted to the left guys this is Sarah if you haven't met her before we have new people in the

front and that's KIRO that's David that's other David that's Malcolm and Joseph andam right

there and there's Mustafa Habibi I know right it's all gonna be gone in like two weeks some people are jacking your spot

br you got to fight him I know so we have effects that push the hemoglobin oxygen dissociation curve to

the right and push it to the left correct we know how pH affects the hemoglobin oxygen dissociation curve how

does it do it when the pH goes down there is more loading or unloading there's more unloading when the pH goes down why does that make sense how are you going to think about that how are you going to remember that

I'm saying when the pH goes down it's going to shift to the right how do we know that CU shifts to the right are offloading oxygen correct and when is a case where the blood pH inside of a

human body goes down during exercise lactic acidosis during exercise the body pH goes down and you have to think we want

more oxygen offloading at that time so this decreases oxygen affinity and increas inrees oxygen off flating at the tissues so an increase in oxygen

Affinity would be caused by a increase in PH correct so what's happening inside the red blood cell we're holding on to this

we're holding on to this we're not making H+ which means the pH isn't going down right so the pH isn't going down

then what the pH is going up and that means it's increased oxygen Affinity not decreased because the pH would have to go down to to decrease the oxygen

Affinity this is incorrect so the answer is C but why what does an enzyme inside the red

blood cell have to do with CO2 in tissues well you need to know how red blood cells work feel free to move forward if you

like I write a little small I know that there's a seat right here seat right there how do red blood cells work because obviously they swap the

oxygen for the CO2 right how do red blood cells work the question isn't how do they work CU anyone could tell you that oh it drops off the oxygen it picks up CO2 and it leaves and then goes to L yay right

like anyone could tell you that a fifth grader could tell you that but how does it actually work well the red blood cell picks up CO2

from where the tissues from respiration and the CO2 isn't held as CO2 it uses Carbonic and hydrates to

turn the CO2 into H2 CO3 and turn that into bicarb the major and this is the fact this is what all of this was leading up to the majority of CO2

carried by red blood cells is carried in the form of bicarb the majority of CO2 carried by

red blood cells is carried in the form of bicarb so if you inhibit Carbonic and hydrates you limit the amount of bicarb that can be made you limit the amount of

CO2 that can be carried and you limit the pickup of CO2 from the tissues thus increasing CO2 in the periphery

yes I'm guessing you wouldn't have that on the question would that you would not have this graph on the question you would have to be in your head I know that us this typ elimination process you

don't see oygen there so of right exact I think the kicker to think about oxygen and how it plays a role in this

is this the fact that it's happening inside of red blood cells sorry oh because if you can't use Carbonic and

hydr the whole reason that CO2 decreases pH is because the CO2 turns into H+ and H3 minus and the H3 minus goes away

right it's the whole reason that that happens the reason I said that there was an increase hold on first of all not necessarily that there's an increase in

PH I'm saying that to decrease the oxygen Affinity we have to decrease the ph and make more H+ since that's not happening there is no decrease in oxygen

Affinity is what I meant right I said theoretically if we were to go the opposite direction that's just a logic thing that if you want to disprove something you prove that the opposite is

true right that's that's something we did a lot in philosophy you want to prove a point prove that the opposite is or could be true sorry you want to disprove a point

prove that the opposite is or could be true all right the question was if you inhibited Carbonic and hydrates inside of red

blood cells which of the following would happen Carbonic and hydrates fun fact is also the most catalytically efficient enzyme in the entire

body what do catalytic efficiency K cat over km or sorry yes

that's C efficiency K cat over km wonderful very good that's the bicarb buffer what's the other buffer we have

in our body the phosphate buffer and since I told you the pka of the bicarb buffer we can look at the pka

of phosphate buffer we start with phosphoric acid which turns

into monobasic phosphate which turns into dibasic phosphate which turns into phosphate and for

poly for for polyprotic acids that kind of dissociate in this manner this is the rule that the pka will increase by approximately five

points for every deprotonation from 2.2 to 7.2 to 12.2 so I ask

you I ask you what is the predominant species of phosphate in your

body A B C or D what is the predominant species of phosphate in your body it would be not

b c y c so 7.2 7.2 is right here 5050 right why do

we know that cuz phal PKA plus log a minus over ha a and

if a minus and ha are equal then this comes out to zero right and pH equals

PKA so if the pH 7.2 equals 7.2 right this would be 50/50 but it's not we are saying that

7.4 equals 7.2 plus log blah blah blah blah blah and in order for this to increase that side this needs to be predominant we need more of this and how

are we going to think about that well here's 7.2 on a number scale where is 7.4 to the right or to the left to the right

very good lots of new faces today guess people are really starting to study for the MCAT now either that or you guys are doing your job and you're telling people about

this program who's here on referral

cool I am too I referred myself I referred myself to be your teacher I kind of did all right before I move on now that

there's a significant number of people here is there anything out of any of the you guys can go look back in your notes while I prep the next 10 15 minutes of the lecture all of you guys who have

been here the whole time or been taking notes go back into biology look for something that's confusing and I'll explain it

if you guys would like me to explain anything at all I will explain it today let's talk about digestion real quick just for a bit and one specific

part of digestion the anatomy because unfortunately some of us get by digestive Anatomy no pun

intended so what's the first part of digestion the mouth correct we go from the mouth to the orox which is just that back part of the

mouth right there and then we go into the esophagus the first part of the esophagus is is pretty stiff right hard and then you go down it becomes smoother

smoother muscle is the esophagus always open by the way is the esophagus always open no it has to be forced open and I learned that when I was doing anatomy the esophagus

is normally just this closed little Loop like this and when you swallow it opens up and then closes again it's interesting what is what is the thing that shuts the trachea when you swallow

what's it called eplus the epig Lotus very good it moves forward and closes off the trachea when you swallow and food just slips past the iglus I also forgot this made me remember that you

can the reason why you can also swallow things upside down is because of the involuntary muscle movements peristalsis there is involuntary smooth muscle contraction all along the GI

tract that is called peristalsis you want to give it a shot jump out of an airplane upside down and swallow a chug of water just bring a

parachute all right so the esophagus the esophagus leads into to the stomach the upper part of the stomach and the stomach has four

parts and we're going to write out the four parts so let's just say this is the esophago sorry the gastro esophago

Junction or the gastric spincter right whatever it's called I forget I should know this but I don't so the first part of the stomach is called

what the fundus then we have the body and then then the

antrum and then the pylorus do you guys like I don't know if you guys like it or not so I won't do it if you don't like it but do you guys

like it when I give you medical knowledge that relates to your lesson yeah there is a disease in children called pyloric

stenosis pyloric stenosis and before you move on from the pyloris you need to pass the pyloric sphincter and it is a muscular sphincter

that controls the output of gastric contents into the what's the first part of the small intestine the dadum so before things get out to the dadum they have to pass through the

pyloric sphincter what is stenosis what is aortic stenosis mitro stenosis pyloric stenosis it's a closure right it's it's

like a stiffening right aortic stenosis is a stiffening of the aortic valve so blood can't really get out of the aorta pyloric stenosis is a stiffening of the pyloric sphincter so it stops contents

of the stomach from getting into the small intestine these kids are going to projectile vomit out the stuff that they eat because it can't get down and the stomach fills and fills and fills and it

causes them to gag all their food out this needs to be surgically managed and the surgery is called a

pylorectomy you cut away muscle from the pyloric sphincter so this is now the small intestine and this is the

stomach so we have the duum and the dadum leads into the jum and the jum leads into the ilium the ilium is the absorption point

of vitamin B12 specifically it's pretty late get issues very good intrinsic factor is required for absorption of vitamin

B12 it's a very characteristic anemia that occurs when you are deficient vitamin B12 is called megaloblastic anemia the ilium

before you move into the next part you have something called the ILO blank valve the ILO seal valve because this next part is

called the seeum and this is now the large intestine otherwise known as the colon the

colon does anyone know what buds off of the corner of the ilocal valve there's this little outgrowth of tissue at the corner

of the seeum I've seen it I've held it the appendix anyone know someone who's got an appendectomy a lot of people lots of

people know someone who got an appendectomy this are probably the most people we had in class before that's nice look at that tell your friends everyone tell your friends to come if they want high yield MCAT facts

thrown at them like boiling hot water please don't throw boiling hot water at anyone this is going to become like the new don't sniff uh what was it don't sniff

acetone because you're talking to orgo about acetone and I was talking about how much I love the smell of acetone don't sniff acetone the seeum then we have the four parts of the well technically there's

five parts of the colon because the seeum is one of them right and where is this in the body if you guys could point to my body where is or your body where

is in the body it's right here the ilocal junction right here right so the seeum is going to bend up towards the body because what's weird is that we

have the stomach here and the small intes just loops and loops and loops and loops and then throws you right here and instead of going straight to the ass we do this whole roundabout thing we do

this entire we do a whole turn around the body because we go under up over down and out so let's think about

that again and the reason I say this the reason I Orient you is because the next part of the colon are referred to by their position so first we have the seeum

which curves us up like a little C and then we have the part of the colon that goes up that's called the ascending colon that next we have the part that goes to

the left this is the transverse colon next we if we had an ascending we have a descending colon and lastly we have something that

Loops down and puts us towards the rectum the sigmoid colon what does a sigmoid curve look like looks like that that's kind of what the

sigmoid colon looks like just not as 2D hopefully and the sigmoid colon leads us

into the rectum or the rectal Vault so why why what's the point why don't we just

go we're right here you just got to make a loop backwards and go why why why does the colon

exist cuz what's absorbed here and what's absorbed here nutrients sugars fats proteins

vitamins Etc out of everything I just named what did I not say water water

reabsorption or absorption not even reabsorption water absorption water is constantly being pulled out of the

gastric and intestinal contents pulled and pulled and pulled and pulled do you know how much water there is in a mushroom you guys ever eaten a mushroom before there's so much water in

there you are pulling it out of all of the food you eat and all the meat and all the beans and all the lentils and all the everything everything that you eat that has any amount of moisture in

it as long as you're not eating chalk it has water in it and you're pulling it out from the food you

eat cuz if you weren't you would die either you'd die or you'd be pissing at your godamn ass which happens when you have diarrhea

cu the bacteria in your gut up your absorption capability and just goes and you start squirting out of your anus you start painting the wall

[Laughter] Brown so if you have a problem up here your stool is going to be fatty you're going to have a problem with fat reabsorption you'll be able to see it fatty stools are a really bad sign in

medicine there could be something pretty bad going on if you have a problem here you have watery stools where modium come in Imodium yeah

is that like H what was em modium again anti anti-diarrheal right I think I think it's over here oh yeah so it's like it's like a osmotic agent and it causes whatever so

if you increase or decrease the osmolarity of like a specific substance inside of here you can increase or decrease the amount of water that goes in or out like a laxative a laxative is

going to be like fiber it just pushes everything along you since it pushes things along it decreases the amount of time you spend here it Waters down the stool and it makes it easier to pass actually haven't read up on a modium in

a while it's been like seven eight months so I'll get back to you on that stay hydrated folks was that a good overview of

digestion are we all sufficiently disgusted okay good wonderful does anyone have anything they want me to explain to them or did you guys forget that I asked

you that question go for KIRO we're all waiting clock's ticking gen bio that do you see the

title Sarah God what's up where's diverticulitis in stach diverticulitis well diverticulitis isn't

Co isn't a stomach problem it's a colon problem so what's a diverticula a diverticula is basically like you have the colon right here get a little out pouching like that it's a

diverticula yes oh Brown fat do you not remember we were talking about Brown fat last time thermogenin I'm surprised it hasn't been

erased yet babies have a lot of brown fat for because they have to keep warm because they're idiots and don't know how to

survive you actually just talked about something that's on my list to cover today so let's talk about Endocrinology let's talk about the center of Endocrinology who is head

huncho of Endocrinology almost the hypothalamus the hypothalamus this word sends Shivers up

my spine because I just took my neuroanatomy practical and the number of times I've had to identify the hypothalamus if I had a nickel I would

probably have 25 nickels exactly I would have $125 it's probably more money than what's in

my bank account right now because I don't get paid to work here I love making that

joke so what are hormones released from the hypothalamus well as an MCAT student it is a bit difficult to think about it from the position of the hypothalamus so

maybe we should start at the pituitary hormone right so the pituitary hormones are flat

Peg from the anterior pituitary and O A from the posterior pituitary so this is anterior and this is posterior front and back and the pituitary it looks like a little ball

sack right and then you have the pituitary stalk which leads up into the hypothalamus right this is the anterior and the posterior pituitary what did I tell you the posterior pituitary was

it's just one giant neuron it's one huge neuron cuz axons from the hypothalamus will come and invade the posterior

pitutary and just send out o and a what are o and a oxytocin and ADH oxytocin is good for one thing on

the MCAT and one thing only and it's not so what's the other thing hm I just said not labor this is the only example

of a positive feedback loop that you need to know what's the positive feedback loop when a baby is ready to be delivered it

will start trying to Crown it will push up against the cervix and cause cervical dilation what is the cervix well these

are the Fallopian tubes and this is the uterus how big is the uterus again did I did I tell you guys when I when I dissected a uterus it's about that big

it's tiny it's really small and that thing that's this big and about that wide in dimension carries a whole human inside of it it's ridiculous shout out

to our women all two of you in the room let's

go here is the end of the uterus and the junction between the birth canal or the vagina and the uterus is the cervix it

is a very small hole that sperm can pass through it is a muscular Junction I believe it's muscular right and what's going to happen is the baby is going to come out of the uterus and push up on

the cervix and that's going to cause cervical dilation that cervical dilation will

signal the hypothalamus and the posterior pituitary to release oxytocin oxytocin will hit the smooth muscle of

the uterus and stimulate its contraction and the stimulation of uterine contraction will dilate the

cervix cause more oxytocin to release more contraction more dilation more oxytocin more contraction more dilation more oxytocin more contraction until the

baby is out and the cervix closes back up completely well after the the placenta and everything comes out right cervix bounds back uterus comes back to

regular size and now the woman is Chu full of this cuddle hormone and the first thing she does is hold this human being that she

doesn't know and boom immediate Bond formation so this is the evolutionary process by which we have developed

bonding between mother and child some also stipulate that the drop in oxytocin after Labor is a big part of the reason for postpartum Blues

yeah yeah because there's still there's still a natural sort of progression there C I don't know I have no idea but there are some pretty cool reflexes inside of newborn babies inside

of babies in general if you stroke the cheek of a baby it'll turn to that side because that's like a breastfeeding reflex so when the nipple touches like the corner of a child's cheek it'll turn towards it it's called The rooting

reflex um another one is the grasp reflex if you guys ever have been near a very very young child you put your finger in a tend it'll close a tand around your finger and it'll actually have quite strong grip for a for a

baby um also if you put a baby underwater it will instinctively hold its breath another one is um the moro reflex it's like the stuttle reflex so if you

take a baby and you hold it don't do this don't don't do this this is done by trained professionals inside of a hospital setting who are ready if the

the baby falls you hold a baby like this and you drop your hand a couple inches and the baby falls back and it spreads itself wide like that to protect from a

fall it's cool right okay so that's the whole thing oxytocin what is ADH again we just talked about ADH before responds to high blood osmolarity right Waters down the blood increases blood volume

etc etc right these are the B of every MCAT student existence unless you use an in which

case you know these by heart let's go through them so first I'm gonna kill myself oh I damn it

I keep forgetting all this is on camera seek help if you need it FSH right follicle stimulating

hormone what's all that yaen no I'm kidding I don't give a I literally don't care follicle stimulating hormone right

FSH who has follicles men or women and when you stimulate the follicles what do they do they release estrogen follicles release estrogen so if it releases estrogen in

women does it release testosterone in men they're opposite it doesn't release testosterone in men what does testosterone in men luteinizing

hormone this does testosterone in men this does estrogen in women which means this luteinizing hormone does progesterone in women and follicle

stimulating hormone does what in men spermatogenesis DHT is a testost derivative and it's the reason you and I are going to go bald

somay unless you book a flight to Turkey you pay a guy a thousand [Laughter] bucks follicle stimulating hormone and lutenizing hormone

we I would love to go over the menstrual cycle again I have a whole 28 minute lecture about it on my YouTube Channel watch it if you have to it is part two of chapter 2 of General biology it was

uploaded late because I had to re-record it my audio cut out the first time so what's the a in flat Peg and give me the full name no

a none of that adreno corticotropic hormone adreno

corticotropic hormone acct break down the name adreno cordico

Tropic adreno meaning adrenal gland cortical meaning cortisol Tropic meaning it gets someone

else to do its bidding and then yeah Tropic and what's doing the bidding cortisol it is a

corticotropin right so what does ACT do when it's signal I love how I just had the drawing of the ball sack on this on the Whiteboard for like the past 15 minutes so adrenocorticotropic hormone

is released from the pituitary in response to what from the hypothalamus no there is a hormone that controls the Tropic

hormone CR corticotropin releasing hormone I think it is yeah CRF I was just that's what I was thinking about I was like there's something wrong

corticotropin releasing Factor my bad CRF stimulates the pituitary to release act act circulates through the

bloodstream and hits the bean and his friend who's the friend the adrenal

gland now the question I ask every single student and they hate me for it which part of the adrenal gland is it

hitting the outside or the inside and if I called them by their names the answer would be obvious the outside why because the

outside's called the cortex and it makes cortisol and other steroid hormones so it's going to hit the cortex and release

cortisol if I were to zoom in on this which you will do in medical school this is the cortex and this is the medulla similar to the posterior

pituitary the medulla is one ginormous neuron one huge neuron and this is the site of what synthesis give me the fancy

word catac colomine catac colomine synthesis and the cortex has three layers the first layer does

salt the second layer does sugar and the last layer does

sex there is a constant orgy going on in that third layer just pound town no but it actually controls the production of a very specific Androgen

called andrena which is important more for women than for men because men produce more most of their androgens in the testes women are dependent a little bit

more than men on the function of the third layer of the adrenal cortex for the production of andr andion to turn into estrogen then camine synthesis down here

what do the camines norepinephrine epinephrine dopamine more specifically norepinephrine epinephrine cool so cortisol released from the second layer of the adrenal cortex cortisol regulates

what sugar balance correct and stress this morning when I was awake at 6:45 right because I had my exam I woke

up at 6:45 and I walk into the exam Hall and my friend Dan walks in great guy I love him he's a really really nice person wants to be an opthalmologist I hope it works out for him he comes in

he's like I just had so much coffee man so much so awake right now before the exam and I am sitting there trying not to fall asleep at 8:15 in the morning

it's about like orientation is at 8:30 for the for the exam I was and I'm just like I'm waiting and he's like what are you waiting for I was like I'm waiting for my cortisol to kick in why why should you not drink coffee first thing

in the morning you're tired because when you wake up at hour zero when you wake up at hour zero what wakes you up cortisol if

you wake up naturally corol wakes you up and it slowly starts to climb and it hits a peak about 2 hours after you're awake and then it just slowly starts to

dip and it slowly starts to climb again which is why you'll realize like seven eight hours after you've been awake you're kind of tired like 2 3 p.m. 400

p.m. you're kind of tired again but if you make it past that if you make it to 7 8 900 p.m. oh my God what time is this

lecture wow oh man did I coordinate this lecture to be part of your natural sleep wake cycle no I didn't this is just when I was

free but if you make it past that you're fine you hit your second wind the cortisol kicks back in and wakes you

up right yeah so if the thing is if you drink caffeine here yeah you're going to hit a high high you're going to hit a high high but this isn't going to feel like awake anymore so if that doesn't

feel like a wig the is this gonna feel like you're gonna feel like my guy you be like

garbage iist to HS great hours after you wake up exactly because your cortisol level is spiked two hours after you wake up so how about morning people because

they're not normal people that just wake up andul morning people I mean like everyone has a different level of sort of like cortisol blah blah blah and your body adjusts whatever you do so if you're a morning person you've been a

morning person your body's going to adjust to that right I'm not a morning person I'm most certainly not a morning

person I wish I was but that's also why I want to become a surgeon because I can just be like oh you guys need me to wake work until 5: in the morning and then go home for the rest of yeah sure why not I go

okay adrenocorticotropic hormone the T TSH correct what is TSH

is it thyroid stimulating hormone or is it thyrotropin no it's thyroid stimulating yeah what was thyrotropin that was TR thyrotropin releasing hormone from the

hypothalamus so before we get to the hypothalamus let's figure out this flat and then what's the peg the three kind of

unknowns right prolac endorphins and growth hormone I learned this unit in medical school that endorphins actually act on

the same receptors as opium heroin Codine they're literally just natural opioids

it's crazy it is called the if you want to do research on it it's called the MU opioid receptor the MU opiod receptor by the way what does mu mean in

physics micro so what's a micrometer 1 time 10 to the what meters

six and what is this what's this and then what's this negative

one what goes in between here centimeter and what's this and then after that I think it's

fomer I think that's 15 cool someone had a question no okay okay

so talked about that okay prolactin milk production and what inhibition of other sort of menstrual

and sexual hormones so we talked last time about a patient that I saw in a neurosurgery Clinic 37y old man very young healthy works out a lot etc etc

came in with erectile dysfunction 37y old guy erectile dysfunction and headaches and he was what he had

enlargement of his breasts got chasa nope he had a tumor and that tumor was secreting

prolactin which was killing his sex drive causing gamasa yes I know that some tumors aren't cancerous right so that's not that's not

a cancerous tumor a prolactinoma is a benign tumor of the pituitary so that's called a that's it's of a subtype of tumor it's a subtype of a tumor called a

pituitary adenoma and usually om means not malignant a pituitary adoma right there's a buch of different types of pituitary adomas you can

research them they're quite interesting but this one secreted prolactin right how do you inhibit

prolactin we have a whole prolactin inhibiting factor in our body also known as dopamine very good dopamine

endorphins painkillers and growth hormone causes linear growth okay AB b c and

d who can tell me what secretes what what secretes a what secretes these

two huh the full name ganat tropin releasing hormone

what secretes B we talked about it before corticotropin releasing Factor what secretes

C this is one a lot of people forget thyroid tropin releasing hormone Gat tropen gonat tropen releasing hormone give you a moment to take everything down okay

genotropin releasing hormone corticotropin releasing Factor thyrotropin releasing hormone and the last one what secretes growth hormone this is the easiest

one growth hormone releasing hormone very good yeah no idea I wish I knew but I do know that the secretion of growth hormone and growth factors in general is a very

complicated study if I were only an inch taller I'd be six feet tall exactly right just start shooting up

growth hormone come on just one more I have a friend with a growth hormone deficiency I mean she had a growth hormone deficiency now she's

fine she actually had to take semental growth hormone as a kid so she's like 5'7 she quite tall for a woman my

original was 52 crazy look at that my mom my mom is 53 but she has scoliosis and she's 5'3 so she was supposed to be 56

okay so that is our overview of Endocrinology by the way if you didn't know f l a t in flat these are the Tropic hormones and Peg those are the

direct hormones F L A are your tropic hormones and Peg are your direct

hormones what time is it by the way 750 70 7:30 okay better to freak out if it was 750 holy

time flies when you're having fun yay I'm having so much fun my back doesn't hurt at

all by the way if you are planning to take the MCAT in April May or June which is most of you

I'm assuming I would suggest taking a half or fulllength diagnostic at some time within the next two three weeks and coming back to me with your score to

talk about it have fun and if you're at home email me or text me I sign off on my emails with my phone number which I probably should stop doing because there's like

70 people on that email thread now but no one's killed me yet please don't kill me earlier good

catch real quick what's the difference that and thisis which one's

controlled apoptosis is controlled and the MCAT loves the word

programmed programmed cell death programmed by who the mitochondria the Andria is really really heavily implicated is really heavily implicated

inside of aop to how are you gonna remember that because if you up your mom wants to kill you hello Laura you walked in at a great time it's

good to see you again Nicole crw back we were talking earlier about how mitochondria come from your mother right

so mitochondria controls apoptosis if you mess up your mom's going to kill you necrosis is uncontrolled cell death and that's where cells just they just

die lack of oxygen too many toxic factors they just die this there's like a whole process of the cell losing its nucleus and this and that blah blah blah

and it doesn't explode or anything or and it just shrivels up and it dies this splatter everywhere there's red sirens

and alarms going off and everything and that's why necrosis usually comes in a group there's a group of cells that are

just because there's so much stuff that just gets tossed out of the cell yes like the back's back like BCL 12 no

you don't no you will in medical school but you don't know that for

a child comes to your clinic with bow legs bow legs their growth has been abnormal and their height is stunted or their growth has been stunted their

height is abnormal which of the following is most likely to be high in this patient first you have to diagnose the kid and it's a diagnosis we've

spoken about before a fat kid NOP it's a baby a kid like a kid kid what does the kid have have

hello everyone hello hello welcome oh really I'm Yousef how are you guys um as time goes on honestly the lectures

might get shorter so we might start at 7 instead of instead of 6 would you guys mind terribly going from 7: to 9:30 instead of 6 to like 8 :30 all right so

we'll push up by an hour we'll do 7 to 9:30 starting next week because I will not be here on Thursday I have two 4our exams on Friday no sorry I have two two and a half hour exams on Friday I have a

4 Hour exam next week huh yeah I've so these two weeks I have six exams over two weeks I had one

yesterday I have one today I have two on Friday well Tech more than six exams one one yesterday one today two on Friday two on Monday one on Thursday one

on Friday and then I leave then I'm away for a week parathyroid parathyroid hormone what do a kid have

yeah no you would think you would think it's growth hormone because their growth is stunted right but the bow legs that's a really strange finding

rickets the kid has rickets good job what is rickets Bon the bones of brittle why the kids's not getting enough of a specific

vitamin vitamin D rickets is a vitamin D deficiency in children specifically in adults it's called something different does anyone know

what it's called in adults osteal AA Osteo Malaya we'll talk about that in a second what's the answer to the

question whoa hold on hold on all right who thinks it's a no one who thinks it's

B no one who thinks it's C no one two three anyone four five

five oops who thinks it's D one 2 3 four five six why is it D why is the answer D well

vitamin D is essential for what calcium uptake from small intestine so if you lack vitamin D you

have low calcium from the intestine which means you have low calcium in the blood do you want to tone down serum calcium when you have low calcium no you

want to start wasting those bones so when you waste the bones away and the child tries to move around or stand or move its legs or do anything and the

bones are brittle they flex and they Flex Inward and you get bow legs

that's right right no not at all please totally I mean that's the number one risk factor for osteoporosis in the future obese weight the number one

reason that people have osteoporosis is because of obesity because you're putting more and more and more pressure on those joints and those joint spaces begin to close every single time you

climb I think it's up it's either up or down the stairs you put three to four times your body weight on one leg on one

hip and knee that's a lot of weight that is a lot of weight to put on one joint I'm 165 pounds what's four *

165 a lot you taking the elev no you guys like this good

cool that brings me to another Point some vitamins that you should maybe be aware of not even vitamins you should be aware of just just small facts about

specific vitamins number one vitamin A what's it good for lots of things anyone who likes skin care should know that vitamin A is great for getting

rid of pigmentation right retinol retino retinol and retinoid and retinol derivatives I just made a video about on my Tik Tok the other day right but vitamin A specifically for the

MCAT is really good to make retinal and retinal is a visual pigment

Vision or retinoic acid I think it's like 11 cyst and then all trans there's like that that change that happens when the light IR radiates that double

bond and there's ropin and the retinoic AES connected to ropson and the confirmational change of the retinoic AES caus the ropin and change which activates the G protein coupled receptor G protein coupl receptor sends a signal

through the retina onto the optic nerve through the brain to the occipital lobe and you see an image that's a retinoic

acid vitamin B which one which one all right so let's let's do some really really quick facts vitamin B2 is

a component of what fad and fmn this is riboflavin right B2 B3 is a

component of niin which is part of NAD and nadp+ is that why you when you take a

lot of nin get yes you flush it's a side effect of nin nin's also good for uh LDL control cholesterol control

B5 co-enzyme a panic acid it's part of co-enzyme a Coen is a huge molecule massive absolutely

massive B7 B6 you don't really need to know much about it that's the thing P Panic acid is B5 pyxine is

B6 what's B7 good for biotin is good for hair B9 and b12 everything literally everything

especially having children I up last time in in the video I I like the time that I was talking about B9 B12 um I want to correct myself because I correct myself

in the sheet I don't know if you guys look at that all the time I said that B12 deficiencies will cause neural tube defects and then I said because the baby

eats up the folate first of all B12 isn't folate B9 is folate and folate is the correct term B9 deficiencies will cause central nervous system problems

inside of the child when they're born that's why it's kind of recommended that any sexually active woman of childbearing age hopefully you're of

childbearing age if you're sexually active right should be taking folate supplements because if they get pregnant you don't want any risk that the baby comes out

up okay that's vitamins that's more biochem than it is bio oh sorry that's not all the vitamins um vitamin D we said is for calcium

uptake and where do you get vitamin D from guys touch grass go out in the sun touch some grass don't sit at your computer all my all my uh computer science friends are just like oh bro I

have to take like 25,000 pills of vitamin D every day or else I'm going to shrivel up like a worm and die I was like bro can you go work outside can can you can you go somewhere do something

with your life and vitamin K which I want to mention to you what's it good for I was going to touch on the vitamin professor said that it's a hormone it's not really a

vitamin no specific is deoy 125 well yeah like like Cal calcitriol is is vitamin D but

it's not really a hormone like it's a signaling molecule like it can be used that way but because not even like vitamins are co-actors that's the thing about vitamins that they're co-actors to

enzymes and processes so vitamin K vitam K do clotting I think it's two SE if my memory doesn't fail me

27 9 12 protein C and protein s and these are all the clotting factors that are

dependent on vitamin K no I'm flexing on you for no

reason um and specifically warin is a drug given that inhibits the Regeneration of vitamin K so it decreases those clotting factors and

that's how it controls coagulation who here knows their blood type tell me your blood type oh negative tell me your blood type B positive just like

me a positive anyone else O positive just like my dad anyone else tell they don't tell you what do you mean they don't tell you so

many what the do you mean they don't tell you just ask you ever donated blood before they tell you when you donate blood they give you a

card hold on I do honestly great business model A lot of people would buy into that where the hell there we go Blood

Donor be positive unless they stop giving those out because they're cheap cheap okay so how does this work what is

the inheritance of a and o antigen well first of all what are they right they are antigens that exist on the surface

of your red blood cells and there are so many of them there's tens of them right but you only need to know a couple so let's say you have a red blood

cell let's say you have the a antigen and how am I going to repr resemble the a antigen with an A and and you have another red blood cell and you got a

B and then you got another red blood cell and you got an O something's wrong here who can tell me what's wrong who's

been paying attention the O antigen doesn't exist the o means zero zero antigens we'll get

there people with the a antigen make what antibodies their antibodies are not B they're antib and hold on let me draw this a

little better so you know it's an antibody and not a y is that good okay what about these guys their antibodies are

anti- a and these guys make anti- a anti B all right how do you inherit them well

here's my dad and here's my mom what does I I mean o type blood and there's my sister and there's

me that's how you inherit them so I have a recessive antigen for ootype blood that's how you inherit them what about that Rh factor

what is that right so the only thing you need to know about the Rh factor right is that some people are RH positive and some

people are RH negative and Rh negative people don't really like RH positive blood so much so that if a mother who Rh

negative gives birth to an RH positive child and their blood mixes the mother will start creating antibodies against

Rh factor now the Rh negative mother has antibodies against the Rh factor so if she gets pregnant again and that baby is

RH positive that baby going die unless you have modern medicine

yeah I forget I totally forget what it's called but some sort of crazy very scary disease name y the plus minus is the Rh factor so I'm

B positive which means I have Rh factor and if you're let's say something negative let's say we become blood brother brothers I slit my hand you slit yours we shake hands right your body

will immediately start creating antib is against that Rh factor in my in my body right so now let's talk about AB B O whatever I'm positive right I on my way

home get stabbed by a and I'm I'm bleeding out on the ground cuz look at how many people are laughing now so a little a little three foot6

person comes up behind me jumps up and stabs me in my back right all right and and now and now I'm bleeding out on the floor EMT comes they're's

like oh my God he's dying and the only blood that they have is aye blood and they pump me full of it what's going to happen well I'm B

I have anti-a antibodies antibodies are going to surround the red blood cells and when the antibodies Sur around the red blood cells that's called opsonization when antibodies flood and

stop something and then my immune system is going to destroy those red blood cells I can't even use them I can't use them them there's no point what if they give me B type blood do I have anti-b

antibodies no or else I destroy my own blood right what did they give me O type blood well there's no antigens there so there's nothing to destroy so I can

accept B type blood O type blood and I'm RH positive so that means I can accept RH positive blood and I can accept Rh negative blood given that the Rh

negative donor doesn't have Rh antibodies or they've been sifting out of their blood which probably happens when you donate blood if you do have them in the first

place okay what about this guy anyone here have a Ty blood no let's talk about Laura so Laura is gon to walk home and get stabbed by a and she's she's

just bleeding out on the floor and I'm like oh my God Laura I'll save you so I hook a needle into my arm and put one right in left Atrium and I'm

just like pushing really hard and the blood just starts flowing out of my arm and into her left atrium is she going to be okay why cuz look a type people make

anti-b B type people make anti-a AB people make nothing she's going to be completely fine no matter who gives her blood especially since she's positive

she's RH positive so RH positive people Rh negative people and old type people and a type people and B type people and stupid people and and everyone everyone can give her blood

anyone right as long as you don't have AIDS don't give Laura blood if you have AIDS what about O type blood who you and

Sarah you two you are both walking home and you get shot by a right right in right in the

aorta right luckily a c thoracic surgeon is just it just happens to be walking next to you repairs the aort and just grabs a bag of blood out of his car

starts transfusing unlucky for you I'm sitting in the car pushing blood out of my body right unlucky for you why because you make anti-a and anti-b

antibodies so when I give you my B type blood it's gone in seconds and when Laura gives you her blood with A and B and it's gone in even less seconds and

then when someone else with a Ty blood gives you their a type blood it's gone in even less sec in whatever right it's gone is the point you can only receive

blood from people with O type blood because why because you make antibodies against all other types

of blood except o so the thing is people with the Rh factor can we donate to people with Rh negative blood we could if it's their first exposure probably

because it takes time to mount that response right maybe they'd be okay but better not to so RH positive people can donate to RH positive people Rh negative

people can donate to everyone which is why David is the most valuable person in the room right now I'm

not man that guy Dave is g to walk watch me get stabbed and just be like haha I'd probably be laughing too not

gonna lie oh finally yesid run can't run that fast I mean come on we did

antigens uh it is what do you mean what do you mean where did they come from do they they like crawl out of little holes in

the ground like what the it's called it's called a condro plaia shout yo shout shout out to any midgets back home bro we with you a

condro plasia a contro plagia who's that who's that Game of Thrones um actor yeah yeah I've never never watch Game of

Thrones it's it's it's just porn for like two it's like for the first two seasons it's just porn on

TV n bro bro come on don't do that I don't watch White Lotus either do I look like I do I look like I have time to watch

Game of Thrones I I don't have I don't have time dude I spend my free time teaching you about midgets

okay I'm going to go home and study I have work to do I have an exam in two days let's talk about Action

potentials let's talk about Action potentials and action potential propagation because I feel like this is a simple enough concept that too many people forget way too many people forget

right so let's talk talk about it okay which way is depolarization Which Way Is repolarization Up Is deole Down is

repole and then below Baseline is called hyper Poole right okay so Baseline is70

molts threshold is 50 molts Max is positive 35 molts and Hyper Poole I think is like 85 negative 80

something like that let's just call it negative 80 so at the head of the a on at at the head of the neuron right we have a neuron cell

body we have a long axon and we have all these dendrites I'm going to pimp you guys about a lot of information about this axon so be

prepared this is the cell body this is the axon these are the dendrites and the dendrites are part of the pre synaptic

neuron there is a neuron following this if there's a neuron following this it is called the post synaptic neuron if it's not a neuron it's a muscle usually and

then it's not called the synapse it's called the neuromuscular Junction okay a neuromuscular Jun is a specific type of synapse between a PR synaptic neuron and its

eector so temporal and spatial summation of all bunch of different impulses coming in if the summation of those impulses is high enough to go to

threshold potential the neuron does what it opens what type of channels sodium channels right sodium in

sin right and then pottassium out pout sin pout right so we open the sodium

channels are they fast to close or slow to close they are fast to close or be inactivated right then as we come here the neuron

needs to reset set everything right because we have this massive influx of positive charges so we're going to push a bunch of positive charges out in order

to get back to resting potential so in an effort to do that it opens potassium channels right and what is it that forces all the sodium in is the sodium

high outside the cell or inside the cell sodium is high outside so there's a lot of pressure against that sodium channel right it's like you guys ever been out in like Williamsburg or

downtown Manhattan on a Saturday night and you see like here's the door here's the door to the shittiest Club you've ever seen your entire life and there's a

swarm of people if they open that door boom gone right everyone's going in this is the club this is the club and the

sodium's trying to get in and the moment the sodium gets in the potassium the smart guy's like I'm getting the out of here I'm done I don't want anything to do with this right so when you open the pottassium

there's a lot of potassium in here right now you open the door boom it goes to reverse way but the potassium channels are what slow to close or quick to close

slow to close so they overshoot the balance they overshoot that resting potential and now you got to do work to

get back to resting potential and that work is done through what sodium

potassium atpa sodium potassium pumps that's it that's the whole shebang right now I'm going to pimp you

guys about the neuron what are these no what are these no nodes of r

VA we'll get there the nodes of Ron VA the nodes of Ron VI are the unmated sections of the

axon the unmated sections of the axon cuz right what is myin it's an insulator right it's

basically made of fat does fat conduct electricity no no fat does not conduct electricity right it's it's just it's just a bunch

of it's made up of a bunch of lipids sphingomyelin right spingo lipids so it's not going to conduct the electricity but one thing that does happen is that when the electro impulse

begins it's going to hop these nodes of Rona it's going to hop the noes of R and that's faster it's not just faster here's the interesting thing they always teach you on the MCAT that it's faster it is faster but it's not just faster

it's more efficient because what's going to happen right let's say I'm the action potential

right and let's say from here to there is a mile from here this side of the room to that side of the room is a mile and I have to Sprint the mile as quickly

as I possibly can right so when I begin there I'm Full Speed Ahead but what happens when I get here I'm slow I'm

tired I'm exhausted so it's possible that if we were to travel down the entire axon we would lose some of the energy of the potential we want to

conserve as much of the energy in the signal as possible so we jump between those nodes so the the actual distance

that's traveled is far far far less than the actual distance of the axon number one number

two sodium and potassium all along here what's the important ion there calcium there's calcium release that

allows for vesicles filled with neurotransmitters to associate with the end of the neuron and be released into the synapse this is the cell body correct

right here this general area what's it called the Soma yeah but the axon hilock the the beginning of the axon where all

of that summation takes place right one more thing if this neuron is in the central nervous

system what type Ty of cells are making the myin alod dendrites these are the cells that are destroyed in what

disease no no yes multiple sclerosis multiple sclerosis is a central nervous system dementing disorder

and it comes and it goes and it comes and it goes and it comes and it goes if this were in the peripheral nervous system what cells are affected what

cells make the myin the peripheral nervous systeman cells what disease or disease process destroys Swan cells no

gon guon bar what about diabetes it can diabetic neuropathy yeah diabetes is a lot of things

nephropathy retinopathy neuropathy diabetic foot disease blah blah blah BL blah

yeah I'm so bad at that stuff I'm not going to lie to you like the only thing I know about the refractory period is that it's like the sodium pottassium pump action the absolute refractory

period is absolutely no signal can be transmitted the relative refractory period is like okay we've we've garnered enough stability so if you kick me in

the balls I'll do something like normally you just need to like poke the neuron to do it if you're in the relative refractor period you have to like stab it and then it'll do

something don't stab neurons do not do not stab yourself in the head great advice from

YF all right one final thing that we'll go over and then we'll we'll chat as a group for a couple minutes and then you guys can go home I

promise this he not a sperm cell it's bacteria the bacteria enters your body

right and it's foreign who going to eat it probably a maccrage

num nom right a maccrage also known as an antigen presenting cell it's going to chop up the bacteria right preserve its

antigen and use what to display it MHC Class 2 why two because two is the exogenous pathway outside

and the mhc2 is recognized by what t- cell CD4 which is the helper t- cell which is

going to blow a horn and cause B cells to copy the antigen go to the lymph noes replicate the antigen attach it to uh made antibodies produce antibodies

against that bacteria produce the antibodies send out the antibodies opsonize the bacteria and terminate the infection rather let's

say let's say a virus gets in your body and it takes its this is your cell it takes its DNA and injects it into your cell and it

begins assembling viral particles well before those viral particles get out your cell inside has another his compatibility complex in it

what's it called MHC one those viral particles get chopped up the antigens get attached to mhc1 and are produced and presented on the

cell and that production and and the display of the antigen activates what cd8 t- cells killer te- cells and

they're going to blow the horn and be like holy you need to die you need to die right why because if you you don't die then you're going to die and

leak all of this virus all over the body so the cdat cell comes injects the cell with proapoptotic factors boom dead and goes on to recognize more of

those an and boom dead boom dead boom dead boom dead and some cells can even when they have some viruses are so smart but we're

smarter well maybe sometimes some viruses will downplay

mhc1 will decrease the transcription and ability of mhc1 to do its job any cell with downregulated

mhc1 dead any cell with downregulated mhc1 dead gone because you can no longer

do your job your body is the strictest Factory in the entire world you can't do your job

done finished huh NK cells yeah that is it for biology review thank you guys so much for watching everyone

here stick around for a few minutes