Bladder distention triggers sympathetic outflow at which spinal levels to maintain detrusor relaxation?

• A. T11-L2
• B. T1-T4
• C. L2-S2
• D. S2-S4

Answer: (A)

During bladder filling, the body shifts into storage mode. Afferent signals from bladder distention activate a thoracolumbar sympathetic outflow, with fibers arising from the T11 to L2 region traveling through the hypogastric nerves to the bladder. The detrusor muscle is relaxed by these sympathetic fibers via beta-adrenergic receptors, while internal sphincter tone is maintained or increased by alpha-adrenergic effects, supporting urine storage. This thoracolumbar pathway contrasts with the sacral parasympathetic drive (S2–S4) that promotes detrusor contraction for voiding. Hence, the level range responsible for maintaining detrusor relaxation during bladder distention is T11 to L2.