Question

question 20

the heart is innervated by _____ nerves.

a) parasympathetic
b) sympathetic
c) both parasympathetic and sympathetic
d) neither parasympathetic nor sympathetic

Explanation:

Identify the physiological control of the heart

The heart's rate and strength of contraction are regulated by the autonomic nervous system (ANS). The ANS consists of two main divisions: the sympathetic nervous system and the parasympathetic nervous system.

Analyze sympathetic innervation

Sympathetic fibers innervate the heart via cardiac nerves arising from the cervical and upper thoracic ganglia. These nerves release norepinephrine to increase heart rate and force of contraction.

Analyze parasympathetic innervation

Parasympathetic fibers reach the heart via the vagus nerve (Cranial Nerve X). These fibers release acetylcholine to decrease heart rate.

Determine the combined innervation

Because the heart requires dynamic regulation to both speed up during exercise (sympathetic) and slow down during rest (parasympathetic), it receives dual innervation from both divisions of the autonomic nervous system.

Answer:

• A) parasympathetic
• B) sympathetic
• C) both parasympathetic and sympathetic (Correct answer)
• D) neither parasympathetic nor sympathetic