Which of the following is true of autonomic innervation of effectors?

• A. Somatic motor neurons innervate all autonomic effectors.
• B. Autonomic innervation only affects skeletal muscles.
• C. Autonomic effectors are only innervated by the sympathetic division.
• D. Most effectors receive dual innervation from both sympathetic and parasympathetic divisions.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of autonomic innervation. The autonomic nervous system (ANS) controls involuntary functions and is divided into two main branches: the sympathetic and parasympathetic divisions. These divisions work together to regulate the activity of effectors such as smooth muscle, cardiac muscle, and glands.
2. Step 2: Clarify the role of somatic motor neurons. Somatic motor neurons are part of the somatic nervous system, which controls voluntary movements of skeletal muscles. They do not innervate autonomic effectors, which are controlled by the autonomic nervous system.
3. Step 3: Examine the statement about autonomic innervation affecting skeletal muscles. Skeletal muscles are not autonomic effectors; they are controlled by the somatic nervous system. Autonomic innervation primarily affects smooth muscle, cardiac muscle, and glands.
4. Step 4: Analyze the claim that autonomic effectors are only innervated by the sympathetic division. This is incorrect because most autonomic effectors receive dual innervation, meaning they are influenced by both the sympathetic and parasympathetic divisions. These divisions often have opposing effects to maintain homeostasis.
5. Step 5: Conclude that the correct answer is: 'Most effectors receive dual innervation from both sympathetic and parasympathetic divisions.' This reflects the cooperative and antagonistic roles of the two divisions in regulating autonomic functions.