The preganglionic parasympathetic neurons controlling the urinary bladder detrusor muscle are located in:

• A Sacral spinal cord segments S2–S4 (intermediolateral grey) ✓
• B Lumbar segments L1–L3 (intermediolateral grey)
• C Dorsal motor nucleus of the vagus nerve
• D Inferior mesenteric ganglion

Explanation

Parasympathetic preganglionic neurons for the bladder detrusor reside in the intermediolateral grey matter of sacral segments S2–S4 (pelvic splanchnic nerves, nervi erigentes). Their axons synapse on short postganglionic neurons in the pelvic ganglia or within the bladder wall. The detrusor is the primary muscle of bladder emptying and its contraction is mediated by M3 muscarinic receptors. Sympathetic supply (L1–L3) promotes bladder filling by relaxing the detrusor (beta-3) and contracting the internal sphincter (alpha-1). The vagus does not supply pelvic organs below the left colic flexure.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.