Blasenreflex

Blasenreflex, or the bladder reflex, refers to the neural circuits that regulate the storage and voiding functions of the urinary bladder (micturition). It involves sensory input from the bladder wall, spinal reflex pathways, and autonomic and somatic output that control the detrusor muscle and urethral sphincters.

During bladder filling, stretch receptors in the bladder wall send afferent signals via the pelvic nerves to the sacral spinal cord (S2–S4). The storage phase is supported by sympathetic outflow (hypogastric nerves) that relaxes the detrusor and maintains internal sphincter tone, and by somatic control via the pudendal nerve that keeps the external urethral sphincter contracted. Supraspinal centers modulate these processes to prevent involuntary voiding.

Voiding is initiated when the brain coordinates a switch from storage to micturition. The pontine micturition center in the brainstem integrates signals from higher centers and, when appropriate, triggers parasympathetic outflow to the detrusor, causing contraction. At the same time, the internal sphincter relaxes and the external sphincter can be voluntarily relaxed under pudendal control to allow urination. Thus, the micturition reflex couples detrusor contraction with sphincter relaxation.

Clinical relevance includes disorders of the reflex pathway, such as overactive bladder, urinary retention, and neurogenic bladder following spinal cord injury or neurologic disease. These conditions reflect impaired coordination between storage and voiding components of the Blasenreflex.