SPINAL CORD REPRESENTATION OF MICTURITION REFLEX

The spinal cord origin and peripheral pathways of the sensory and motor nerves to the urinary bladder were delineated in the cat by stimulating the appropriate nerves near the urinary bladder and recording from the dorsal and ventral rootlets near the spinal cord. The parasympathetic preganglionic neurons originated in the sacral segments of the spinal cord and reached the bladder by way of the pelvic nerve. The preganglionic parasympathetic perikarya to the urinary bladder were distributed over a length of approximately 1.5 segments, centered near the junction of segments S‐2 and S‐3 in cats with a median arrangement of the lumbosacral plexus. Conduction velocities in preganglionic parasympathetic fibers to the bladder ranged from 46 to 2 M/sec with a mean maximal velocity of 18.2 M/sec. The major sympathetic pathway to the bladder was in the hypogastric nerve. Preganglionic sympathetic fibers originated in the lumbar spinal cord and traveled through the caudal mesenteric ganglion and hypogastric nerve to the urinary bladder. There were both ipsilateral and contralateral preganglionic and afferent fibers in this pathway. The preganglionic sympathetic neurons originated in segments L‐2 and L‐5. They were usually distributed over approximately 2 full segments centered near the junction of L‐3 and L‐4 in cats with a median arrangement of the lumbosacral plexus. Neurons involved in the micturition reflex may extend from the rostral end of the L‐2 segment to the caudal end of the S‐3 segment. The sympathetic preganglionic neurons were usually separated from the somatic and parasympathetic columns by segments L‐5 to L‐7. Copyright © 1969 The Wistar Institute Press