Bowel and bladder control involve spinal reflex pathways that are located in the sacral region of the spinal cord. In both instances, two sphincter muscles, an inner sphincter of smooth muscle and an outer sphincter of skeletal muscle, control the passage of waste out of the body. How would completely severing the spinal cord at the lumbar level affect an individual's bowel and bladder control?

Question

What will be an ideal response?

Answer 1

The person would still exhibit a defecation (bowel) and micturition (bladder) reflex because the spinal reflex is
processed at the local sacral level of the spinal cord, which is intact at that level. Efferent impulses from the organs would stimulate specific interneurons in the sacral region that would synapse with the motor neurons controlling the sphincters, thus bringing about emptying when organs began to fill. This is the same situation that exists in a newborn infant who has not yet fully developed the descending tracts necessary for conscious control. The individual with the spinal cord transection would lose voluntary control of the bowel and bladder because these functions rely on impulses carried by motor neurons in the brain that must travel down the cord and synapse with the interneurons and motor neurons that are involved in the reflex. With a lumbar transection, these impulses no longer reach the reflex control center.