1. Are there two means by which the centers of intrafusal fibers can be stretche

Question

1. Are there two means by which the centers of intrafusal fibers can be stretched?

a. no, application of external force is the only means

b. yes, neurosecretion from -motor neurons induces stretch as well as external force

2. Does excitation-contraction coupling occur by the same mechanism within intra- and extrafusal muscle fibers?

yes or no

3. Does excitation-contraction coupling yield the same outcome in extra- and intrafusal muscle fibers?

a. yes, affected cells contract

b. no, only the ends of intrafusal fibers contract whereas the entire extrafusal fiber contracts

4. Do intrafusal fibers express nicotinic acetylcholine receptors?

yes or no

5. What is the fate of acetylcholine within any neuromuscular junction?

a. hydrolyzed by acetylcholinesterase

b. reuptake

Explanation / Answer

ans 1  yes, neurosecretion from -motor neurons induces stretch as well as external force.

ans 2 -- excitation-contraction coupling yield the same outcome in extra- and intrafusal muscle fibers.

ans 3 --- no, only the ends of intrafusal fibers contract whereas the entire extrafusal fiber contracts.

ans 4 ---NO intrafusal donot express nicotinic acetylcholine receptors , but they are present on extrafusal muscle cells.

ans 5 ----- reuptake . receptor structure with a single-bound ligand keeps Acetylcholine in the synapse that might otherwise be lost by cholinesterase hydrolysis or diffusion. The persistence of these acetylcholine ligands in the synapse can cause a prolonged post-synaptic response.

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