Final answer:
The Spinal micturition center, located in the sacral spinal cord, reflexively controls urination but can also allow for voluntary control by modification from higher brain centers. This intricate process includes stretch receptors in the bladder and the coordinated action of both involuntary and voluntary urinary sphincters.
Step-by-step explanation:
The Spinal micturition center or sacral micturition center refers to a group of neurons in the sacral region of the spinal cord that are responsible for controlling urination. This center generally acts reflexively, ensuring the process of voiding urine occurs automatically. However, higher brain centers can modify its action to allow for voluntary control over urination. This is critical in the process of potty training where children learn to assert external sphincter control to delay voiding. The normal micturition process involves a complex interplay of neural signals and sphincter musculature. Stretch receptors in the bladder wall sense bladder filling and trigger a reflex that involves the parasympathetic nervous system, resulting in detrusor muscle contraction and internal urethral sphincter relaxation. Additionally, during the bladder filling phase, sympathetic nervous activity and somatic control maintain continence through the contraction of the external urinary sphincter and suppression of the detrusor muscle.