Organismal Biology/Physiology Thread

[QofQuimica]

All users may post questions about MCAT, DAT, OAT, or PCAT organismal biology (anatomy, physiology, development, embryology, and evolution) here. Cellular bio, molecular bio, and biochemistry questions should be posted in the other biology thread. We will answer the questions as soon as we reasonably can. If you would like to know what biology topics appear on the MCAT, you should check the MCAT Student Manual (http://www.aamc.org/students/mcat/studentmanual/start.htm)

Acceptable topics:
-general, MCAT-level biology.
-particular MCAT-level biology problems, whether your own or from study material
-what you need to know about biology for the MCAT
-how best to approach to MCAT biology passages
-how best to study MCAT biology
-how best to tackle the MCAT biological sciences section

Unacceptable topics:
-actual MCAT questions or passages, or close paraphrasings thereof
-anything you know to be beyond the scope of the MCAT

*********

If you really know your organismal biology, I can use your help. If you are willing to help answer questions on this thread, please let me know. Here are the current members of the Organismal Biology Team:

Maddscientist (thread moderator): Maddscientist is a Ph.D. student in developmental biology.

TheDarkSide: TheDarkSide has several years of experience working as a nurse. She scored 12 on the BS portion of the MCAT, and 37 overall.

Occasional moderator: Shrike. Shrike is a full-time instructor for The Princeton Review. His primary expertise is in other subjects; he knows just enough biology to have scored 12 on the BS section without ever having studied organic chemistry.

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[minsoox1983]

You are on the right track, but you are double counting. For instance, ABC and BAC are the same genotype. Basically, you are counting
permutations, but you should be counting combinations. With combinations, the order doesn't matter. Don't write out all the possibilities because that's too time consuming. Instead, realize that you have AaBbCc and you need a genotype with 3 chromosomes. So for chromosome 1 one can you choose a or A, for chromosome 2 you can choose b or B, and for chromosome 3 you can choose c or C. So the "base" is number of choices for each chromosome and the "exponent" is the number of chromosomes the genotype needs.

2*2*2 = 2^3 = 8.

wow,, now i understood !
i wasn't sure if the order of chromosome combination didn't matter.. 2*2*2.. thank you!!


I got one more question for you brokenglass..
I just wanted ask your passage reading strategy for biological sciences.

For me,, most of time, i take about 10 minutes to finish all the discretes.. (sometimes 12minutes if i struggle a bit..)

Then i jump to passages, and do orgo passages first since these passages are quite short (usually take about 5 minuest to finish). I just read the figure/ equation/ chart/ graph and then do the questions. and then i move on to biology ones, in which i glance thru the contents b4 the questions.

Yet, here is my problem.. i tend to just read the key words and find out what concepts of this psg is all about.. It works if the questions are not so much about "based on the experiments" But in the last practice test i took, they had three biology experimental passages with lots of "based on the experiment" questions and analysis-application questions which take me enormous time since i have to go back and re-read/understand the experiment then /think/predict then read the answer choices..

I usually get to finish all the questions in time even with many experimental passages,, but i wish i have more spare time, optimally about 10 minutes!

What is your strategy ?

 

[BrokenGlass]

wow,, now i understood !
i wasn't sure if the order of chromosome combination didn't matter.. 2*2*2.. thank you!!


I got one more question for you brokenglass..
I just wanted ask your passage reading strategy for biological sciences.

For me,, most of time, i take about 10 minutes to finish all the discretes.. (sometimes 12minutes if i struggle a bit..)

Then i jump to passages, and do orgo passages first since these passages are quite short (usually take about 5 minuest to finish). I just read the figure/ equation/ chart/ graph and then do the questions. and then i move on to biology ones, in which i glance thru the contents b4 the questions.

Yet, here is my problem.. i tend to just read the key words and find out what concepts of this psg is all about.. It works if the questions are not so much about "based on the experiments" But in the last practice test i took, they had three biology experimental passages with lots of "based on the experiment" questions and analysis-application questions which take me enormous time since i have to go back and re-read/understand the experiment then /think/predict then read the answer choices..

I usually get to finish all the questions in time even with many experimental passages,, but i wish i have more spare time, optimally about 10 minutes!

What is your strategy ?

Sorry, I cannot help you there. I haven't take the MCAT yet and I haven't done any passages yet. I am still in the process of reviewing the basic science that MCAT tests. You may want to read Qofquimica's posts regarding strategy.

 

[minsoox1983]

that is surprising.. but i'm sure you 'll get well above 12+ . You are extremely smart and helpful . Thank you and good luck to you too!

 

[Krazykritter]

Minsoox,

Just my unsolicited advice on strategy & the advice given to me by lots of sources (Kaplan included); Do not skip around. If you do want to leave a question blank, mark it but do not skip around looking for passages in different disciplines. You will be wasting time & it may stress you out on the test day to be skipping through a whole bunch of questions & that is the last thing you want. Generally, they do not recommend leaving any questions blank at all & going through in order.

By the way, this is the advice given for the COMLEX/USMLE (Same for MCAT when I took it on paper 4 years back).

 

[BrokenGlass]

Minsoox,

Just my unsolicited advice on strategy & the advice given to me by lots of sources (Kaplan included); Do not skip around. If you do want to leave a question blank, mark it but do not skip around looking for passages in different disciplines. You will be wasting time & it may stress you out on the test day to be skipping through a whole bunch of questions & that is the last thing you want. Generally, they do not recommend leaving any questions blank at all & going through in order.

By the way, this is the advice given for the COMLEX/USMLE (Same for MCAT when I took it on paper 4 years back).

I read somewhere that the surest way to increase your score on ANY standardized test is to answer MORE questions correctly

 

[bluesTank]

Need someone to just make sure I have this straight:

In regards to the ovulation process:

First of all, is estradiol the same thing as estrogen, when it is talked about in a discussion?

Secondly, is it that estradiol/estrogen stimulates LH production, but also inhibits it's secretion until it reaches a threshold where it stimulates it's secretion in the luteal surge? Just need some clarification on this, thanks

 

[BrokenGlass]

Need someone to just make sure I have this straight:

In regards to the ovulation process:

First of all, is estradiol the same thing as estrogen, when it is talked about in a discussion?

Secondly, is it that estradiol/estrogen stimulates LH production, but also inhibits it's secretion until it reaches a threshold where it stimulates it's secretion in the luteal surge? Just need some clarification on this, thanks

Estradiol is a type of estrogen.

Granulosa cells around a follicle grow and convert more and more testosterone to estrogen. HIGH levels of estrogen have a POSITIVE feedback on hypothalamus and anterior pituitary. (LOW levels of estrogen have a NEGATIVE feeback on hypothalamus and anterior pituitary). Due to positive feedback, anterior pituitary produces more LH, resulting in the luteal surge. Luteal surge causes ovulation.

Following levels of estrogen is the key to understanding the ovarian cycle.

Does this answer your question?

 

[Bonbon2007]

What is the correct route for deoxygenated blood from the heart to the lungs and then back to the heart? TY. very much appreciated.

 

[BrokenGlass]

What is the correct route for deoxygenated blood from the heart to the lungs and then back to the heart? TY. very much appreciated.

The right half of the heart pumps blood into the pulmonary circuit via the pulmonary artery to the lungs and back to the heart via the pulmonary vein.

Pulmonary Artery receives oxygen-poor blood from the right ventricle and transports it to the lungs.

Pulmonary Vein receives oxygen-rich blood from the lungs and transports it to the left atrium.

The route for blood from the heart to the lungs and then back to the heart is:

Right Ventricle -> Pulmonary Artery -> Arteries -> Arterioles -> Capillaries -> Venules -> Veins -> Pulmonary Vein -> Left Atrium

 

[ocwaveoc]

Hi all,
To what level of detail should we know cellular respiration?
1) # of ATP generated at each step?
2) # of NADH/FADH2 produced at each step?
3) # of ATP produced by each NADH/FADH2?
I'm familiar with the mechanism of what occurs....just not the exact numbers of the above produced and when they are produced at what number.
Thanks

 

[rcd]

Wtf is the kidney.

The descending tubules concentrate filtrate, I understand that much. But what's the point since the ascending tubules just dilute it? Is it all about Na+ reabsorption?

And how does aldosterone increase BP? I understand that H2O needs to flow out down its concentration gradient since you're decreasing its filtrate concentration (thus, increasing body water, increasing BP), but without ADH, H2O won't flow anywhere worth a darn after the descending tubule.

 

[BrokenGlass]

Wtf is the kidney.

The descending tubules concentrate filtrate, I understand that much. But what's the point since the ascending tubules just dilute it? Is it all about Na+ reabsorption?

And how does aldosterone increase BP? I understand that H2O needs to flow out down its concentration gradient since you're decreasing its filtrate concentration (thus, increasing body water, increasing BP), but without ADH, H2O won't flow anywhere worth a darn after the descending tubule.

The role of the loop of Henle is to concentrate the medulla (i.e. to increase solute concentration in the medulla) so that when ADH acts on the collecting duct, water diffuses out of the collecting duct, producing concentrated urine...

I believe aldosterone causes Na+ reabsorption at the distant convoluted tubule. Water then follows Na+, so blood volume increases thereby raising blood pressure...

 

[corbis11]

for aldosterone, look up the renin-angiotensin system up on wikipedia. It has a pretty good diagram of how aldosterone is called in and helps elevate blood pressure

 

[CATallergy]

I am having trouble making this connection.

It seems like, if anything, they should cause hypokalemia.

why not:
decreased angiotensin II -> increased adrenocortical stimulation -> more aldosterone -> higher potassium excretion from more Na/K pumping

 

[corbis11]

I am having trouble making this connection.

It seems like, if anything, they should cause hypokalemia.

why not:
decreased angiotensin II -> increased adrenocortical stimulation -> more aldosterone -> higher potassium excretion from more Na/K pumping

ACE inhibitors block angiotensin II production which is a major stimulator for aldosterone release from the adrenal cortex. Since a function of aldosterone is to secrete K+ while reabsorbing Na+ (H2O follows) a decrease in aldosterone will cause less K+ to be secreted so it will accumulate and hypokalemia could occur if too much of the ACE inhibitor is administered. That's how I rationalize it...

 

[subi]

Reproductive system..

what could be the cause for the infertility in a diabetic man who has normal healthy sperm count??

How can one determine the genetic sex of an individual by examining the cell from buccal mucosa?

 

[BrokenGlass]

Reproductive system..

what could be the cause for the infertility in a diabetic man who has normal healthy sperm count??

How can one determine the genetic sex of an individual by examining the cell from buccal mucosa?

Do you mean cause of infidelity?

 

[eiman]

inhalation of 100% oxygen is contraindicated for a patient who has

1. pneumothorax
2. acute bronchitis
3. acute viral pneumonia
4. chronic obstructive lung disease (correct)

why??

 

[BrokenGlass]

inhalation of 100% oxygen is contraindicated for a patient who has

1. pneumothorax
2. acute bronchitis
3. acute viral pneumonia
4. chronic obstructive lung disease (correct)

why??

Is this really an MCAT question? It sounds like something taught in med school.

 

[pandulce321]

I know ADH directly causes water reabsorption from the collecting duct and distal tubules.


Now aldosterone causes Na reabsorption in the distal tubule, but is water reabsorption a secondary result of the Na reabsorption?


In other words, if you were asked "what increases water retention in the kidney, would it be both ADH and aldosterone, or only ADH?"

 

[BrokenGlass]

I know ADH directly causes water reabsorption from the collecting duct and distal tubules.


Now aldosterone causes Na reabsorption in the distal tubule, but is water reabsorption a secondary result of the Na reabsorption?


In other words, if you were asked "what increases water retention in the kidney, would it be both ADH and aldosterone, or only ADH?"

Both

 

[scotties123]

CBT 10 has a question that basically asks: "all of the following would significantly impaired from liver damage except:"
A) absorption of fats in small intestine
B) production of bile
C) detoxification of poisons
D) regulation of blood pressure

I know B and C would be impaired. I know that bile impairment would have an effect on absorption of fats in the small intestine, but i dont see absorption of fats as a DIRECT effect. I figured that A was the answer because I had read in exam krackers that Albumin (the major osmoregulatory protein of the blood) is made in the liver. The solution says that regulation of blood pressure is NOT a function of the liver.
Im confused. clarification please? Thanks.

 

[BrokenGlass]

CBT 10 has a question that basically asks: "all of the following would significantly impaired from liver damage except:"
A) absorption of fats in small intestine
B) production of bile
C) detoxification of poisons
D) regulation of blood pressure

I know B and C would be impaired. I know that bile impairment would have an effect on absorption of fats in the small intestine, but i dont see absorption of fats as a DIRECT effect. I figured that A was the answer because I had read in exam krackers that Albumin (the major osmoregulatory protein of the blood) is made in the liver. The solution says that regulation of blood pressure is NOT a function of the liver.
Im confused. clarification please? Thanks.

I agree with the solution. Blood pressure is regulated by the kidneys, not the liver.

 

[scotties123]

I agree with the solution. Blood pressure is regulated by the kidneys, not the liver.

yes, but if albumin is the major osmoregulatory protein of the blood and its produced by the liver, then how isnt blood pressure regulated by the liver?

 

[BrokenGlass]

yes, but if albumin is the major osmoregulatory protein of the blood and its produced by the liver, then how isnt blood pressure regulated by the liver?

The question asks about SIGNIFICAT impairment. So while albumin is produced in the liver and does play an important role in the regulation of the osmotic pressure of blood, regulation of blood pressure would not be significantly impaired. Kidney plays a much bigger role in blood pressure regulation.

On the MCAT, we need to choose the best answer, not an answer that is absolutely true in every possible sense. So I still agree with the sample solution.

Absorption of fats in small intestine, production of bile, and detoxification of poisons are affected much more than blood pressure
if liver is damaged.

 

[DrShoshana]

This might be a dumb question. Last year I was in an upper level biology class and we learned about totipotency vs. pluripotency. Is this the same thing as determinate cleavage vs. indeterminate cleavage? Two words for the same concept or is there a substantial difference?

 

[axp107]

Right Ventricle -> Pulmonary Artery -> Arteries -> Arterioles -> Capillaries -> Venules -> Veins -> Pulmonary Vein -> Left Atrium

I know its an old post but I believe you have that down wrong.

Its: Right Ventricle -> Pulmonary Artery -> Lungs -> Pulmonary Vein -> Left Atrium ->Left Ventricle ->Aorta -> Arteries ->Arterioles->Capillaries->Venules->Veins -> BACK to RIGHT side of the heart



Can someone explain the difference between Calcitonin and Parathyroid Hormone?

Calcitonin reduces blood Ca2+ levels

Parathyroid increases blood Ca2+ levels

What does this mean though?? in terms of the effects they have.. ?

 

[scotties123]

Calcitonin reduces blood Ca2+ levels

Parathyroid increases blood Ca2+ levels

What does this mean though?? in terms of the effects they have.. ?

just like u said, PTH increases blood calcium levels. It does so by promoting absorption of Calcium in the intestine, reabsorption in the kidneys, and resorption of bone by promoting osteoclast activity.
Calcitonin basically works in the reverse to decrease blood calcium levels.

 

[axp107]

just like u said, PTH increases blood calcium levels. It does so by promoting absorption of Calcium in the intestine, reabsorption in the kidneys, and resorption of bone by promoting osteoclast activity.
Calcitonin basically works in the reverse to decrease blood calcium levels.

Osteoclast breaks down bone right.. so the Ca2+ released enters the blood then?

Also what benefit does having more Ca2+ or less Ca2+ have ... is there any effect on skeletal muscle contraction

 

[BrokenGlass]

Osteoclast breaks down bone right.. so the Ca2+ released enters the blood then?

Yes.

Also what benefit does having more Ca2+ or less Ca2+ have ... is there any effect on skeletal muscle contraction

Plasma calcium concentration is very important for many reasons. Yes, Ca2+ plays a very important role in skeletal muscle contraction. Sarcoplasmic reticulum is full Ca2+ ions. When an action potential reaches the sarcoplasmic reticulum via T-tubules (transverse tubules), Ca2+ gets out of sarcoplasmic reticulum into the cytoplasm. There it binds to troponin, a protin which moves tropomiosin (another protein which is wrapped around actin) out myosin's way so that myosin heads can bind to actin filaments and the muscle can contract.

 

[wes431]

Which of the following cell types most likely contain adrenergic receptors (receptors that respond to epinephrine)?
A) chromaffin cells
B) sympathetic postganglionic neurons
C) parasympathetic postganglionic neurons
D) cardiac muscle cells (answer)

I don't understand why B isn't the answer because sympathetic postgangionic neurons release epinephrine and norepinenphine therefore they should have adrenergic receptors.

 

[gridiron]

Which of the following cell types most likely contain adrenergic receptors (receptors that respond to epinephrine)?
A) chromaffin cells
B) sympathetic postganglionic neurons
C) parasympathetic postganglionic neurons
D) cardiac muscle cells (answer)

I don't understand why B isn't the answer because sympathetic postgangionic neurons release epinephrine and norepinenphine therefore they should have adrenergic receptors.

Hey! Sympathetic postganglionic neurons run to the effector organ--an example is cardiac muscle. Neurotransmitter that is released by the postganglionic neurons bind to receptors on the effector organ. That is why D is the answer.

 

[wes431]

Hey! Parasympathetic postganglionic neurons run to the effector organ--an example is cardiac muscle. Neurotransmitter that is released by the postganglionic neurons bind to receptors on the effector organ. That is why D is the answer.

I still don't get it because parasympathetic postganglionic neurons release acetylcholine only, therefore it would have cholinergic receptors, NOT adrenergic.

 

[gridiron]

I still don't get it because parasympathetic postganglionic neurons release acetylcholine only, therefore it would have cholinergic receptors, NOT adrenergic.

I edited my above post---meant sympathetic

 

[gridiron]

I still don't get it because parasympathetic postganglionic neurons release acetylcholine only, therefore it would have cholinergic receptors, NOT adrenergic.

To be a little more specific---adrenergic receptors are targets of catecholamines (ex. is epinephrine). There are many types of receptors but the two main types are alpha and beta. An example of a cell which possesses a adrenergic receptor is a cardiac cell.

I also edited my original post--I meant sympathetic

 

[wes431]

To be a little more specific---adrenergic receptors are targets of catecholamines (ex. is epinephrine). There are many types of receptors but the two main types are alpha and beta. An example of a cell which possesses a adrenergic receptor is a cardiac cell.

I also edited my original post--I meant sympathetic

Oh so I think I got it. The question asks for the "cell type" that contains adrenergic receptors. But ganglionic neurons aren't cell types and don't themselves contain adrenergic receptors. They only form a synapse with adrenergic receptors. Therefore that only leaves answers A and D. But chromaffin cells are modified postganglionic neurons that release epi or norepi with adrenal medulla as the effector organ. Leaving D as the answer. Is that right?

 

[ashley]

i'm having trouble getting a hold on the menstrual cycle, particularly the hormone changes and interactions. to make matters worse, I tried looking up alternate explanations to get a fresh approach, but they don't exactly coincide.

does anyone know a good place I can look for a clear explanation, or can you guys offer tips on how to remember aspects of it?

thanks!!!

 

[gridiron]

Oh so I think I got it. The question asks for the "cell type" that contains adrenergic receptors. But ganglionic neurons aren't cell types and don't themselves contain adrenergic receptors. They only form a synapse with adrenergic receptors. Therefore that only leaves answers A and D. But chromaffin cells are modified postganglionic neurons that release epi or norepi with adrenal medulla as the effector organ. Leaving D as the answer. Is that right?

Yes--the question asked for a "cell type."

 

[Creightonite]

Hi, i go a question:

Mostly, hormones are protein-based molecules. I just wanted to list the steroid-based ones for the completeness:

-progesterone
-estrogene
-testosterone
-cortisol
-aldosterone

Any additions?
Thank you.

 

[corbis11]

*The Pituitary gland hormones are peptide hormones (PP-oxytocin, ADH)(AP-FSH, LH, prolactin, GH, TSH, ACTH)
*Adrenal Cortex - Steroid hormones (DHEA & Androstendione, aldosterone[acts via second messengers], cortisol)
*Adrenal Medulla - Amine hormones (Epi and or Norepi)
*Thyroid gland - Amine hormones (T4 and T3) & Peptide hormone (calcitonin)
*Parathyroid gland - peptide hormone (parathormone)
*Pancreas - Peptide hormone (insulin and glucagon)

 

[corbis11]

i'm having trouble getting a hold on the menstrual cycle, particularly the hormone changes and interactions. to make matters worse, I tried looking up alternate explanations to get a fresh approach, but they don't exactly coincide.

does anyone know a good place I can look for a clear explanation, or can you guys offer tips on how to remember aspects of it?

thanks!!!

I would recommend googling the menstrual cycle and memorize how the hormones (FSH, LH, estradiol, and progesterone) change when one or more change. Notice how that medium to normal levels of estradiol feed-back inhibit LH and FSH while very high levels of estradiol(from a dominant follicle) result in the "LH surge" which results in ovulation. estrogens and progesterone are released by the corpus luteum which thickens the endometrium and prepares it for pregnancy so that a fertilized egg will stay in the uterus. If no conception occurs, the corpus luteum degenerates due to estrogens and progesterone levels decreasing. If conception occurs, then human chorionic gonadotropin is secreted by the embryo which allows for continues production of progesterone to allow the continued growth of the corpus luteum and continued elevated levels of progesterone and estradiol. These elevated levels have a feed-back inhibition of FSH and LH to prevent another follicle from maturing and ultimately another ovulation from occurring(this is what birth control basically does)

 

[GoldenSunGirl88]

I was wondering what the difference between these two structures are, other than they are located in diff areas of the brain? The medulla and hypothalamus both seem to regulate heart rate, breathing, etc. Is there a way to tell them apart by what they do?

 

[gridiron]

I was wondering what the difference between these two structures are, other than they are located in diff areas of the brain? The medulla and hypothalamus both seem to regulate heart rate, breathing, etc. Is there a way to tell them apart by what they do?

Hey!

Medulla oblongata: serves as a relay station between the brain and the spinal cord--relay of nerver signals. Controls certain autonomic functions of the body--contains cardiac centers and controlls reflexes such as coughing.

Hypothalamus: homeostasis regulation of the body--equilibrium of the body, kind of like housekeeping of the body. Supports activation of the autonomic and parasympathetic nervous systems. Most important function is to maintain the balance of the body--like the blood pressure, temperature, circadian rhythm.

 

[_T_]

I have a question about one of the qs from AAMC 6

117. If Steve’s blood pressure had increased significantly more than Joe’s increased (other factors being equal) while they worked, what difference in their urinary system function would be expected?

A) Joe’s glomerular filtration rate would increase more than Steve’s would.

B) Steve’s reabsorption rate of glomerular filtrate by the peritubular capillaries would be lower than Joe’s would be.

C) Steve’s reabsorption rate per milliliter of glomerular filtrate by the peritubular capillaries would be higher than Joe’s would be.

D) Steve’s glomerular filtration rate would increase more than Joe’s would.

The answer is D. I was wondering why it couldn't be answer C..the answer reasoning says that reabsorption doesn't play a role in arterial blood pressure..I'm not exactly sure what they're referring to tho..

 

[reine1jb]

I have a question about one of the qs from AAMC 6

117. If Steve’s blood pressure had increased significantly more than Joe’s increased (other factors being equal) while they worked, what difference in their urinary system function would be expected?

A) Joe’s glomerular filtration rate would increase more than Steve’s would.

B) Steve’s reabsorption rate of glomerular filtrate by the peritubular capillaries would be lower than Joe’s would be.

C) Steve’s reabsorption rate per milliliter of glomerular filtrate by the peritubular capillaries would be higher than Joe’s would be.

D) Steve’s glomerular filtration rate would increase more than Joe’s would.

The answer is D. I was wondering why it couldn't be answer C..the answer reasoning says that reabsorption doesn't play a role in arterial blood pressure..I'm not exactly sure what they're referring to tho..

I don't know if I agree with that answer either. If you think about the actions of aldosterone and acting as a pathway to increase Na+ reabsorption to increase blood pressure their answer doesn't make any sense. However, I agree the answer is D. Think about it this way, assuming that Steve's blood pressure is higher he would have a higher glomerular filtration rate (GFR). He does not reabsorb more because of how much faster his GFR is. The channels and mechanisms that control solute reabsorption simply cannot reabsorb as much when the GFR is higher.

 

[corbis11]

I think the answer comes from the fact that steve already has a high PB and they want to know what is going to happen due to this. D is correct if you think in this way while C would be incorrect because reabsorption has already occurred...

 

[_T_]

ah..thanks guys..you explained it better then Kaplan lol

 

[axp107]

When we think of the immune system, are we automatically supposed to think of the lymphatic system (are they the same thing)

I got a practice questions wrong b/c I only associated the lymph system with digestion.

So does lymphatic system = immune system basically?

 

[detvar]

back to that question about GFR that T posted.

can someone please explain again y it's D?

i said B at first...because wouldn't reabsorption decrease if BP is too high? the kidneys would not want to reabsorb as much water in case of high BP right?

thanks

 

[detvar]

wait...unless they're trying to pick at the nuance that reabsorption rate itself can't change since the channels work at a particular speed, BUT the filtration rate can change because more channels can be involved??