Which of the following statements about the parasympathetic nervous system is correct?

Question

BlackTom AI · Accepted Answer

Parasympathetic preganglionic neurons use acetylcholine (ACh) as their primary neurotransmitter, releasing it onto nicotinic receptors on the postganglionic neuron; the postganglionic parasympathetic fibers then also release ACh onto muscarinic receptors on target organs.

1) Relevant knowledge points:
- Autonomic nervous system has two-neuron chains: preganglionic (CNS → autonomic ganglion) and postganglionic (ganglion → effector).
- Both sympathetic and parasympathetic preganglionic fibers release ACh onto nicotinic (N-type) receptors on postganglionic neurons.
- Parasympathetic postganglionic fibers release ACh that acts primarily at muscarinic receptors on effector tissues.
- The adrenal medulla is innervated by sympathetic preganglionic fibers and functions like a modified sympathetic ganglion, releasing epinephrine/norepinephrine into the bloodstream.

2) Step-by-step reasoning to the correct choice:
- The statement to verify: “The primary transmitter released by parasympathetic preganglionic neurons is acetylcholine.” Based on the anatomy and pharmacology above, parasympathetic preganglionic neurons indeed release ACh onto nicotinic receptors in the ganglion. Therefore this statement is true.

3) Calculations: none required; reasoning is conceptual.

4) Why the correct answer is correct:
- It matches established neurophysiology: parasympathetic preganglionic axons are cholinergic (ACh-releasing). This is a fundamental distinguishing feature of autonomic neurotransmission.

5) Why the other options are incorrect:
- Option A: Parasympathetic preganglionic axons do not innervate the adrenal medulla; sympathetic preganglionic fibers do, and they stimulate catecholamine release.
- Option B: While ACh from preganglionic fibers acts via nicotinic receptors in ganglia, ACh released by parasympathetic axons at organs acts mainly through muscarinic receptors — so the statement is false as worded.
- Option D: Innervation density varies by organ; it is not true that every organ has greater parasympathetic than sympathetic innervation.

6) Conclusion: The correct answer is “The primary transmitter released by parasympathetic preganglionic neurons is acetylcholine,” which matches the provided answer.

Which of the following statements about the parasympathetic nervous system is correct?单项选择题

类似问题

Doug has not been the healthiest, and he tells you that he is also on another medication that is a broad-spectrum adrenergic receptor blocker, meaning it will block both alpha and beta adrenergic receptors. What would you predict would be Doug’s autonomic response compare to a normal response?

Based on what you know about the effects of activating these autonomic pathways, which of the following statements most accurately describes the situation?

Question at position 47 What is the parasympathetic nerve supply to the sigmoid colon? L2-L3Greater splanchnic nervesVagus nervePelvic splanchnic nerves

Which one of the following statements about the development of higher cognition is correct?

Which of the following statements about the sympathetic nervous system is correct? 关于交感神经系统，下列哪项陈述是正确的？

In the elucidation of the mechanisms of synaptic transmission, it was discovered the injections of extracts of the adrenal gland into the circulation caused a strong vasoconstriction. Which of the following best describes the likely site of action of these extracts?

The sympathetic nervous system ...

An increase in blood pressure (BP) is likely to result in an increased parasympathetic nervous system outflow and decreased sympathetic nervous system outflow.

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单