Acth ?

[unDRdog]

Ok...from my understanding ACTH acts directly on the adrenal gland to increase the secreation of cortisol. In stressful situations, ACTH lvls rise, causing an elevation of cortisol lvls.....WHY?? Cortisol inhibits glycolysis thus decreasing energy production...right? wouldn't you want energy in a fight or flight situation...I believe i have tied myself into a mental knot.... Would someone please explain this...Why would you want an increase in blood glucose levels in a stressful situation?----thanks

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[G1SG2]

Ok...from my understanding ACTH acts directly on the adrenal gland to increase the secreation of cortisol. In stressful situations, ACTH lvls rise, causing an elevation of cortisol lvls.....WHY?? Cortisol inhibits glycolysis thus decreasing energy production...right? wouldn't you want energy in a fight or flight situation...I believe i have tied myself into a mental knot.... Would someone please explain this...Why would you want an increase in blood glucose levels in a stressful situation?----thanks

Cortisol increases gluconeogenesis, which leads to an increase in blood glucose levels. You would want an increase in blood glucose in a stressful situation in order to have energy to either fight or run away.

 

[unDRdog]

Cortisol increases gluconeogenesis, which leads to an increase in blood glucose levels. You would want an increase in blood glucose in a stressful situation in order to have energy to either fight or run away.

right..however it stops glycoloysis...which produces the energy to runaway...right?

well---some of the energy

 

[engineeredout]

Cortisol has four main actions:

#1: Increased hepatic gluconeogenesis
#2: Increased protein catabolism
#3: Increased lipolysis

All three of these serve to increase energy available

#4: Inhibits immune system function


As for stress, there is either short term or long term stress response:

Short term: Release of catecholamines

Long term: Hypothalamus releases Corticotropic Releasing Hormone (CRH), which stimulates the release of ACTH from the anterior pituitary, leading to increased cortisol production from the adrenal cortex


This is a simplification, but its good enough for the MCAT

 

[Bernoull]

Ok...from my understanding ACTH acts directly on the adrenal gland to increase the secreation of cortisol. In stressful situations, ACTH lvls rise, causing an elevation of cortisol lvls.....WHY?? Cortisol inhibits glycolysis thus decreasing energy production...right? wouldn't you want energy in a fight or flight situation...I believe i have tied myself into a mental knot.... Would someone please explain this...Why would you want an increase in blood glucose levels in a stressful situation?----thanks

Adrenocorticotropic Hormone stimulates the adrenal cortex to release glucocorticoids, e.g. cortisol. For ur 1st Q, ACTH ---> increased Cortisol. Cortisol helps ur body to respond to physical and mental stress, by mobilizing energy sources.

I don't know that cortisol inhibits glycolysis, that's seems incorrect.
The main effect of cortisol is to increase gluconeogenesis in the liver. AAs are mobilized from non-liver sources like skeletal muscle and these AAs are converted to glucose. Lipids are redistributed, and some hydrolysed to FAs for energy production, glycerol from FA metabolism is also a substrate for gluconeogenesis.

Cortisol also inhibits glucose uptake by muscles n adipose tissue. The net effect of all this is to increase plasma glucose levels.

Increase glucose levels are important - as the body's main energy source - to get someone out of physical danger etc..

Hope this helps

 

[G1SG2]

right..however it stops glycoloysis...which produces the energy to runaway...right?

well---some of the energy

Yeah, agree with the above posts. Increased gluconeogenesis + increased catabolism of lipids and proteins for energy would probably outweigh any inhibition of glycolysis (I've never heard of that...)

 

[unDRdog]

EK bio 1001 num 575 explination....i know sounds weird to me also..???????....

 

[G1SG2]

EK bio 1001 num 575 explination....i know sounds weird to me also..???????....

It says "cortisol is a (blah blah)...its principal physiological action is to increase blood glucose levels, thus decreasing glycolysis. Glycolysis occurs in cells that are full of glucose. Cortisol inhibits cellular glucose uptake leaving the sugar in the blood. Insulin, on the on the hand, functions to decrease blood glucose levels, increase glucose reuptake and increase the rate of glycolysis."

That sounds like a poor explanation to me, lol...it leaves the sugar in the blood yet inhibits glucose uptake, so even though we have glucose circulating the blood, no one can uptake it?! Unless they mean it inhibits the uptake of glucose by cells that don't need it (cells that are full of glucose and are wasting it away on glycolysis). Makes no sense to just leave it in the blood, since the RBCs would just use them for glycolysis (which cortisol apparently inhibits, so that goes out the window). I think it only inhibits the glucose rich cells from glycolysis, so glucose can be transported to other cells that need it and can undergo glycolysis, respiration, the whole 9 yards.

 

[unDRdog]

It says "cortisol is a (blah blah)...its principal physiological action is to increase blood glucose levels, thus decreasing glycolysis. Glycolysis occurs in cells that are full of glucose. Cortisol inhibits cellular glucose uptake leaving the sugar in the blood. Insulin, on the on the hand, functions to decrease blood glucose levels, increase glucose reuptake and increase the rate of glycolysis."

That sounds like a poor explanation to me, lol...it leaves the sugar in the blood yet inhibits glucose uptake, so even though we have glucose circulating the blood, no one can uptake it?! Unless they mean it inhibits the uptake of glucose by cells that don't need it (cells that are full of glucose and are wasting it away on glycolysis). Makes no sense to just leave it in the blood, since the RBCs would just use them for glycolysis (which cortisol apparently inhibits, so that goes out the window). I think it only inhibits the glucose rich cells from glycolysis, so glucose can be transported to other cells that need it and can undergo glycolysis, respiration, the whole 9 yards.

Bingo!...thats what i think...Its like we have all the cells that are gluttons which are full of glucose and still taking in more of it...lets say for grins that a bear jumps out of the woods and we take off running! Cortisol time: it pulls/stops glucose uptake by these glutton cells and increases blood glucose lvls in order to have an ample supply ammunition (glucose) when needed... The bio book itself states about cortisol: "the benefit of excess cortisol under stressful situations is not fully understood"...leads me to believe we are left to our own shared imagination on here as to why it stops glycolosis....i think you nailed it with that explination...thats what i was thinking also!

 

[G1SG2]

Bingo!...thats what i think...Its like we have all the cells that are gluttons which are full of glucose and still taking in more of it...lets say for grins that a bear jumps out of the woods and we take off running! Cortisol time: it pulls/stops glucose uptake by these glutton cells and increases blood glucose lvls in order to have an ample supply ammunition (glucose) when needed... The bio book itself states about cortisol: "the benefit of excess cortisol under stressful situations is not fully understood"...leads me to believe we are left to our own shared imagination on here as to why it stops glycolosis....i think you nailed it with that explination...thats what i was thinking also!

awesome!

 

[Bernoull]

Bingo!...thats what i think...Its like we have all the cells that are gluttons which are full of glucose and still taking in more of it...lets say for grins that a bear jumps out of the woods and we take off running! Cortisol time: it pulls/stops glucose uptake by these glutton cells and increases blood glucose lvls in order to have an ample supply ammunition (glucose) when needed... The bio book itself states about cortisol: "the benefit of excess cortisol under stressful situations is not fully understood"...leads me to believe we are left to our own shared imagination on here as to why it stops glycolosis....i think you nailed it with that explination...thats what i was thinking also!

I read some more on cortisol and these things are useful to this discussion:

Keep in mind, ur trying to escape say a physical danger...

1. First response is a nervous one, adrenaline increases plasma glucose, heart & breathing rate, blood flow to critical tissues and restriction to others..

2. Endocrine response builds on the nervous one: cortisol acts on virtually all tissues, it reduces glycolysis in target tissues not critical in ur response to the danger and these tissues switch to fat/protein metabolism. In the liver, cortisol inhibits glycolytic enzymes hence inhibiting glycolysis there.

2. Together with gluconeogenesis, fat metabolism etc, cortisol increases plasma glucose and avails more glucose to the brain and muscles most critical for an escape and reduces glucose use by most other tissues.

3. Since ur trying to escape danger, this is not the time for allergies to flare up or heal wounds so cortisol suppresses the immune response..

All of these work together to ensure a smooth getaway..

 

[unDRdog]

I read some more on cortisol and these things are useful to this discussion:

Keep in mind, ur trying to escape say a physical danger...

1. First response is a nervous one, adrenaline increases plasma glucose, heart & breathing rate, blood flow to critical tissues and restriction to others..

2. Endocrine response builds on the nervous one: cortisol acts on virtually all tissues, it reduces glycolysis in target tissues not critical in ur response to the danger and these tissues switch to fat/protein metabolism. In the liver, cortisol inhibits glycolytic enzymes hence inhibiting glycolysis there.

2. Together with gluconeogenesis, fat metabolism etc, cortisol increases plasma glucose and avails more glucose to the brain and muscles most critical for an escape and reduces glucose use by most other tissues.

3. Since ur trying to escape danger, this is not the time for allergies to flare up or heal wounds so cortisol suppresses the immune response..

All of these work together to ensure a smooth getaway..

well done...very impressive thanks for the input!!!!

 

[deleted252565]

I think in a stressful situation, body shuts down glycolysis in liver cells for the following purposes:
1. Reserve glucose for brain and other tissues that can only use glucose as their source of energy; and liver cells at the same time mobilize fat to generate energy.
2. Body needs a quick source of energy so glycolysis, which takes longer time, is not necessary, so it breaks down glucose stored from muscle cells to produce lactic acid + quick ATP.

I think this is what I have learned in my Biochem class. Hope this help!

 

[G1SG2]

Regarding ACTH-EK audio osmosis says that ACTH only stimulates the adrenal cortex to release glucocorticoids, not mineralocorticoids. Doesn't it stimulate the release of both?

According to wikipedia:

"ACTH acts through the stimulation of cell surface ACTH receptors, which are primarily located on adrenocortical cells of the adrenal cortex. This results in the synthesis and secretion of gluco- and mineralo-corticosteroids,and androgenic steroids."

It stimulates the release of both, right?

 

[Charles_Carmichael]

Regarding ACTH-EK audio osmosis says that ACTH only stimulates the adrenal cortex to release glucocorticoids, not mineralocorticoids. Doesn't it stimulate the release of both?

According to wikipedia:

"ACTH acts through the stimulation of cell surface ACTH receptors, which are primarily located on adrenocortical cells of the adrenal cortex. This results in the synthesis and secretion of gluco- and mineralo-corticosteroids,and androgenic steroids."

It stimulates the release of both, right?

It doesn't have as much of an impact on mineralocorticoid release as it does on cortisol release. Sure, some aldosterone might be secreted in response to ACTH, but ACTH isn't what primarily regulates aldosterone synthesis and release; the aldosterone response to ACTH will be very minimal. Remember that aldosterone secretion is mainly controlled by the renin-angiotensin II system. ACTH mainly influences cortisol secretion.

 

[G1SG2]

It doesn't have as much of an impact on mineralocorticoid release as it does on cortisol release. Sure, some aldosterone might be secreted in response to ACTH, but ACTH isn't what primarily regulates aldosterone synthesis and release; the aldosterone response to ACTH will be very minimal. Remember that aldosterone secretion is mainly controlled by the renin-angiotensin II system. ACTH mainly influences cortisol secretion.

Got it. But if I'm faced with a question that involves both cortisol and aldosterone, should I pick both, since it does have some sort of effect on the latter? Or should I pick cortisol only?

 

[Charles_Carmichael]

Got it. But if I'm faced with a question that involves both cortisol and aldosterone, should I pick both, since it does have some sort of effect on the latter? Or should I pick cortisol only?

For a question regarding the actions of ACTH, I don't know if the MCAT writers would be mean enough to have "Glucocorticoids and mineralocorticoids" as an answer choice while having cortisol as a stand-alone choice as well.

If cortisol was not an answer choice and "aldosterone and cortisol" was a choice, then I'd pick both. I don't know what I would do with cortisol was an answer choice as well; I'd probably pick just cortisol since ACTH affects its secretion the most and hope for the best.

 

[lDanny]

so cortisol and glucagon would both increase blood glucose levels. When would one occur over the other?

 

[dudewheresmymd]

hey everyone, in EK they say that ACTH stimulates the release of glucocorticoids from the adrenal cortex, but not mineralcorticoids (aldosterone).. in this attached question from kaplan, it shows that ACTH simulates the release of aldosterone, androgens, and cortisol. Which is correct?

I originally picked B, but then thought of what EK said, and went with A...

Thanks.

 

[gwjib04]

Do we get sick when we're stressed/tired because of suppressed immune function due to cortisol secretion stimulated by Acth beginning with epipinephrine?

Would've thought hyperglycemia in stress would provide extra nourishment for the WBCs in the blood but I guess not.

Anybody here read The Relaxation Response? pretty interesting and definitely connected

 

[dudewheresmymd]

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