Catecholamines are secerted from the sdrenal medulla in response to a. increased

Question

Catecholamines are secerted from the sdrenal medulla in response to

a. increased secreation of ACTH from the anterior pituitary

b. stinulation of the sympathetic preganglionic neurons leading to the adrenal medulla

c. decreased androgen secretion from the adrenal cortex

d. stimulation by chromaffin-releasing hormone

Why are you able to repeatedly contract and relax your muscles of respiration, allowing you to breathe in and breathe out? Select one

a. As soon as all of the Ca 2+ stored in the lateral sacs of the sarcoplasmic reticulum is used up, muscle relaxation occurs.

b. After the muscle cell becomes excited, acetylcholinesterase rapidly destroys acetylcholine, allowing the muscle cell to return to resting potential

c. Ca 2+ is actively transported back into the lateral sacs of the sarcoplasmic reticulum, and muscle relaxation occurs.

d. Both B and C

e. All of the above

I know C is true for sure, but not too sure if B applies as well.

The regulation of smooth muscle contraction is mediated by the phosphorylation of ____ in response to calcium binding to ____.
a. myosin; calmodulin
b. actin; calmodulin
c. troponin; calmodulin
d. myosin; troponin
e. actin; troponin

Explain why it is A and not D.

Explanation / Answer

1) a.  increased secreation of ACTH from the anterior pituitary

2)d. Both b and c. This is because At the point when there is not any more a nearby activity potential in the muscle cell, Ca 2+ is effectively transported once again into the lateral sacs of the sarcoplasmic reticulum, and muscle relaxation happens

3) a. This is because

Smooth muscle compression is managed by a progression of responses that starts with the binding of calcium to calmodulin. The calcium-calmodulin complex at that point ties to and initiates a protein kinase called myosin light chain kinase (MLCK). MLCK catalyzes the phosphorylation of the myosin light chains (LC20). Once these

light chains are phosphorylated, myosin and actin interaction can happen and the muscle abbreviates and creates tension. Albeit two atoms of ATP are required to start contraction, one for the phosphorylation of myosin light ties and one to twist the myosin cross-bridge, smooth muscle is energitically effective

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