Question

which of the following best demonstrates an example of cooperation between the parasympathetic and sympathetic nervous systems?
parasympathetic stimulation causes vasodilation of blood vessels in the penis, leading to erection; sympathetic stimulation then causes ejaculation.
sympathetic stimulation causes vasodilation of blood vessels in the penis, leading to erection; parasympathetic stimulation then causes ejaculation.
sympathetic stimulation causes vasodilation of blood vessels in the clitoris, leading to erection; parasympathetic stimulation then causes reflexive contractions of the vagina.
parasympathetic stimulation causes copious sweating; sympathetic stimulation causes epidermal pores to dilate.

Explanation:

To determine the correct answer, we analyze the roles of the parasympathetic and sympathetic nervous systems in sexual physiology:

• The parasympathetic nervous system is responsible for vasodilation in the penis (or clitoris) to cause erection (a "rest - and - digest" type of function in this context, promoting blood flow for sexual arousal).
• The sympathetic nervous system is responsible for ejaculation (a more "fight - or - flight" related, but still sexual response, involving muscle contractions and expulsion).

Now let's analyze each option:

• Option 1: Parasympathetic stimulation causes vasodilation of blood vessels in the penis (leading to erection), and sympathetic stimulation then causes ejaculation. This matches the known roles of the two systems.
• Option 2: Sympathetic stimulation is not responsible for vasodilation for erection (parasympathetic is), so this is incorrect.
• Option 3: Sympathetic stimulation does not cause vasodilation for erection, and parasympathetic does not cause ejaculation, so this is incorrect.
• Option 4: Sweating and epidermal pore dilation are not related to the cooperation of these systems in sexual physiology, so this is incorrect.

Answer:

A. Parasympathetic stimulation causes vasodilation of blood vessels in the penis, leading to erection; sympathetic stimulation then causes ejaculation.