After a spinal cord injury, reflexive erection in males requires an intact spinal reflex arc at which levels?

After a spinal cord injury, reflexive erection in males requires an intact spinal reflex arc at which levels?

• A. L1-L3
• B. S2-S4
• C. T10-T12
• D. C3-C5

Answer: (B)

Reflexive erection is driven by a spinal reflex arc that originates with penile sensory input and ends with parasympathetic outflow from the sacral segments. The key players are the afferent signals traveling to the sacral cord and the efferent parasympathetic fibers arising from S2–S4 (the pelvic nerves) that cause dilation of penile arteries and relaxation of the trabecular smooth muscle—producing an erection. Therefore, this reflex can function only if the sacral spinal cord segments are intact; lesions at these levels would disrupt reflexive erections, while intact S2–S4 allow the reflex arc to operate even if higher levels are injured. The other levels (L1–L3, T10–T12, or C3–C5) do not house the essential sacral reflex arc supporting a reflexive erection.

Reflexive erection is driven by a spinal reflex arc that originates with penile sensory input and ends with parasympathetic outflow from the sacral segments. The key players are the afferent signals traveling to the sacral cord and the efferent parasympathetic fibers arising from S2–S4 (the pelvic nerves) that cause dilation of penile arteries and relaxation of the trabecular smooth muscle—producing an erection. Therefore, this reflex can function only if the sacral spinal cord segments are intact; lesions at these levels would disrupt reflexive erections, while intact S2–S4 allow the reflex arc to operate even if higher levels are injured. The other levels (L1–L3, T10–T12, or C3–C5) do not house the essential sacral reflex arc supporting a reflexive erection.