EKBio1001 Endocrine questions

[basophilic]

Question 509: peptide hormone is not functionally active until it leaves which of following organelles
C) Golgi apparatus; correct answer
D) secretory vesicle
Why is D incorrect? Peptide hormones are not "functionally active" when they are stored in a vesicle.

Question 570: Are epinephrine/norepinephrine released together? Is it incorrect to assume this: if norepinephrine is absent from a certain location/organ, then epinephrine will also be absent there? Why?

---

Members don't see this ad.

 

[sc4s2cg]

For 509: remember that the Golgi actually modifies proteins in it and activates them before letting them go in the wild. Thus, they are 'functionally active' in the vesicle as well, its just that they are not necessarily doing anything. In other words the proteins are alert and ready, but there's no danger because the vesicle shields them.

For 570: Ne/E are both secreted from the adrenal medulla (and the ends of certain neurons). I'm not sure on if one is absent will the other as well, I suppose it depends on why they are absent. If the adrenal medulla is damaged, both could be absent. What did the answers say?

 

[basophilic]

For 509: remember that the Golgi actually modifies proteins in it and activates them before letting them go in the wild. Thus, they are 'functionally active' in the vesicle as well, its just that they are not necessarily doing anything. In other words the proteins are alert and ready, but there's no danger because the vesicle shields them.

For 570: Ne/E are both secreted from the adrenal medulla (and the ends of certain neurons). I'm not sure on if one is absent will the other as well, I suppose it depends on why they are absent. If the adrenal medulla is damaged, both could be absent. What did the answers say?

509: I see. I interpreted functionally active to mean actually binding to receptor and initiating signal transduction (since that's a peptide hormone's function). If this is functionally active, is there a special term for a peptide hormone that's actually binding to receptor and doing signal transduction?

570: The answer implied that they are released/function independently; in physio class I'd learned that they're pretty much interchangeable, but guess not
Thanks

 

[sc4s2cg]

I think at that point it is still called functionally active (I mean the term definitely applicable). I don't know if there is a specific term except for "bonding" and similar words. It's a bit like when I'm "ready to eat" and "eating".

I learned the same thing about Ne/E, we weren't specifically told the exact differences. There are some instances where E acts but not Ne, I forget which particular instance but IIRC it is within reproduction.

Sent from my SCH-I545 using Tapatalk

 

[amy_k]

Question 570: Are epinephrine/norepinephrine released together? Is it incorrect to assume this: if norepinephrine is absent from a certain location/organ, then epinephrine will also be absent there? Why?

Firstly, the two hormones Norepinephrine and epinephrine are both produced and secreted from the medulla and circulate in the blood, I believe that epinephrine is usually in higher concentration than Nor-Ep in mammals. This indicates that they are released simultaneously, but in different ratios from the Medulla, with more Ep being released than Nor-Ep, at least in humans. Ep is formed by methylation of Nor-Ep, so this ratio may fluctuate depending on the requirements.

Additionally, Nor-Ep is also produced by brain neurons and functions as a neurotransmitter there. Ep does not act as a neurotransmitter.

In summary, they are chemically different but have the same general effect on the SNS. It is the target location of the two hormones that differs slightly:

Epinephrine binds non-specifically to adrenergic cells in heart, liver, blood vessels, and respiratory muscles to cause vasoconstriction in blood vessels, increase in heart rate and stroke volume, bronchodilation in the respiratory system, and increased blood sugar levels.

Nor-ep is more specific in its targets: increasing cognitive alertness in the brain (fight-or-flight response), and acting on specific adrenergic blood vessel receptors to increase blood supply to skeletal muscle, and is less active (if at all) in the heart, lungs and liver. The difference in Nor-Ep's targets in the adrenal system is thought to be due to it having a higher affinity to alpha adrenergic receptors than beta receptors.

 

[amy_k]

This is way beyond what u need to know about the two hormones, but i hope that gives you some clarity to your question. For MCAT don't consider the specific targets of each just the overall combined effects of both on the SNS.