Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

Which effect does the parasympathetic nervous system have on male sex organs?

1. Ejaculation

2. Orgasm

3. Erection

4. Fertility

The correct answer is: Erection

The parasympathetic nervous system plays a crucial role in mediating the physiological processes involved in male sexual function, particularly during the initial phases of sexual arousal. Its primary effect on male sex organs is the facilitation of erection, which is accomplished through several mechanisms. When sexual stimulation occurs, the parasympathetic nerves release neurotransmitters that cause the dilation of blood vessels in the penis. This vasodilation increases blood flow into the erectile tissues, leading to engorgement and swelling, ultimately resulting in an erection. Additionally, increased blood flow and the subsequent pressure within the erectile tissues compress the veins that typically drain blood away from the penis, further maintaining the erection. While ejaculation and orgasm are predominant effects of the sympathetic nervous system, which is responsible for the later stages of sexual intercourse, the onset of an erection is distinctly governed by parasympathetic activation. Fertility, on the other hand, involves a broader range of physiological and hormonal factors beyond solely nervous system interactions. This intricate balance between the parasympathetic and sympathetic systems highlights the importance of the parasympathetic nervous system in the process of achieving and sustaining an erection, making it the correct choice in this context.