During sexual response, penile erection and ejaculation are mediated respectively by:

• A Sympathetic fibres releasing norepinephrine, then parasympathetic fibres releasing acetylcholine
• B Somatic pudendal motor fibres for both events
• C Parasympathetic fibres releasing nitric oxide, then sympathetic fibres releasing norepinephrine ✓
• D Parasympathetic fibres for both events, via acetylcholine alone

Explanation

Erection is parasympathetic: pelvic nerve fibres release nitric oxide, raising cGMP in cavernosal smooth muscle and producing vasodilatation (the mnemonic 'point'). Emission and ejaculation are sympathetic ('shoot'), via hypogastric fibres releasing norepinephrine that contracts the vas deferens and accessory glands. The pudendal nerve provides somatic motor control relevant to ejaculation timing but not to erection, ruling out option B.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.