All preganglionic autonomic fibers release__at their axon terminals, and the effects are always_ .
(a) norepinephrine, inhibitory
(b) norepinephrine, excitatory
(c) acetylcholine, excitatory
(d) acetylcholine, inhibitory

검증된 단계별 안내

Understand that the autonomic nervous system consists of preganglionic and postganglionic fibers, which release specific neurotransmitters to communicate with their target cells.

Recall that all preganglionic autonomic fibers, regardless of whether they belong to the sympathetic or parasympathetic division, release the same neurotransmitter at their axon terminals.

Identify the neurotransmitter released by preganglionic fibers, which is acetylcholine (ACh). This is a key fact in autonomic physiology.

Recognize that the effect of acetylcholine released by preganglionic fibers on the postganglionic neurons is always excitatory, meaning it stimulates the next neuron to fire.

Conclude that the correct answer must state that preganglionic autonomic fibers release acetylcholine and that the effect is excitatory.

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주요 개념

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Preganglionic Autonomic Fibers

Preganglionic autonomic fibers are nerve fibers that originate in the central nervous system and extend to autonomic ganglia. They transmit signals to postganglionic neurons, initiating autonomic responses. Understanding their neurotransmitter release is key to grasping autonomic nervous system function.

Neurotransmitters in the Autonomic Nervous System

Neurotransmitters are chemical messengers released at nerve terminals to communicate with target cells. In the autonomic nervous system, acetylcholine and norepinephrine are primary neurotransmitters, with acetylcholine typically released by preganglionic fibers and norepinephrine by most postganglionic fibers.

Excitatory vs. Inhibitory Effects

Neurotransmitters can have excitatory effects, promoting action potentials in the target cell, or inhibitory effects, reducing the likelihood of activation. The effect depends on the receptor type and location, influencing how autonomic signals regulate organ function.

All preganglionic autonomic fibers release______at their axon terminals, and the effects are always_____ .(a) norepinephrine, inhibitory(b) norepinephrine, excitatory(c) acetylcholine, excitatory(d) acetylcholine, inhibitory