9.) Motoneurons are specialized to conduct action potentials rapidly. Which type
ID: 3474339 • Letter: 9
Question
9.) Motoneurons are specialized to conduct action potentials rapidly. Which type
of fiber do you expect in motoneurons?
A.) A fibers
B.) B fibers
C.) C fibers
D.) D fibers
E.) all of the above
Activity 8
10.) In the simulation of a chemical synapse, there was no release of
neurotransmitter when there was no Ca++ in the extracellular saline
solution. Why not?
A.) The propagation of action potentials depends on Ca++.
B.) Neurotransmitter channels in the presynaptic membrane are calcium
dependent.
C.) Ca++ is the neurotransmitter and there can be no synaptic transmission in
the absence of Ca++.
D.) The exocytosis of synaptic vesicles requires Ca++.
E.) Ca++ is required for muscle contraction, and muscles in the presynaptic
terminals were unable to pull the neurotransmitter out.
Explanation / Answer
9) Group A fibers are myelinated, with a large diameter and higher conduction velocity as compared to the B and C group of fibers. Since motor neurons are specialized for rapid action potential conduction, it is logical to expect type A fibers (option A) in motoneurons.
10) The release of a neurotransmitter is directly linked to Ca++. Transmission occurs by the secretion of a neurotransmitter into the space between the pre- and postsynaptic surface membrane. The neurotransmitter molecules are stored in synaptic vesicles which release these molecules only after being triggered to do so by Ca++. Thus, in the simulation of a chemical synapse, no release of neurotransmitter was observed as the exocytosis of synaptic vesicles requires Ca++(option D).
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