The somatic and autonomic nervous systems differ in all of the following except:

• A. Whether their actions are voluntary or involuntary
• B. The number of neurons between the central nervous system and the effector
• C. The types of effectors they control
• D. The basic neurotransmitter acetylcholine is used in both systems

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the two systems involved. The somatic nervous system controls voluntary movements and typically involves skeletal muscles, while the autonomic nervous system controls involuntary functions and regulates smooth muscles, cardiac muscles, and glands.
2. Step 2: Identify the differences between the two systems. These include whether their actions are voluntary or involuntary, the number of neurons between the central nervous system (CNS) and the effector organ, and the types of effectors they control.
3. Step 3: Examine the neurotransmitters used in both systems. The somatic nervous system primarily uses acetylcholine to stimulate skeletal muscles, while the autonomic nervous system uses acetylcholine and other neurotransmitters depending on the branch (sympathetic or parasympathetic).
4. Step 4: Recognize that the question asks for the exception — the characteristic that is NOT different between the two systems. Since acetylcholine is used in both systems as a basic neurotransmitter, this is the point where they do not differ.
5. Step 5: Conclude that the correct answer is the statement about acetylcholine usage, as it is common to both the somatic and autonomic nervous systems, unlike the other listed characteristics.