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Briefly describe the neurohormonal process of penile erection
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Correct answer:
Penile erection is dependent on blood flow to the corpus cavernosum. Simultaneous activation of the parasympathetic nervous system outflow from the pelvic nerve and inhibition of the sympathetic nervous system outflow from the hypogastric nerve is necessary for blood to enter the corpus cavernosum. When the parasympathetic nervous system is activated, it inhibits the resting noradrenergic tone of the contracted smooth muscle in the lacunar walls. Nitric oxide acts as the main proerectile neurotransmitter and relaxes the lacunar walls. This allows blood to flow into the corpus cavernosum through the helicine arteries and compresses venous outflow. Norepinephrine is the main antierectile neurotransmitter which contracts smooth muscle in the lacunar walls and prevents blood from entering the corpus cavernosum.
