Question

describe the role of pudendal nerve in micturition reflex

Answer 1

Introduction:

Micturition Reflex-

It is a reflex process through which the urine is emptied (voided) from the urinary bladder.

The organs involved in micturition (excretion) are urinary bladder, urethra and the Sphincters.

Two types of sphincters are involved in our urinary tract:

1. External Urethral Sphincter- It is formed by the circular skeletal muscle and is located at the urogenital diaphragm. It is supplied by the somatic nerve fibres of the pudendal nerve.

2. Internal Urethral Sphincter- formed by the detrusor muscle, situated at the neck of the urinary bladder. It is supplied by the autonomic nerve fibres and it closes the urinary bladder after the bladder is emptied.

Micturition Reflex:-

Nephrons form urine------- urine is collected drop by drop into the urinary bladder---------- when about 200-400 ml of urine is collected into the bladder------- the intravesical pressure increases------ the stretch receptors present on the walls of the bladder get stimulated------- sensory impulses are generated-------- sensory impulses reach the spinal cord( sacral segment) through the pelvic nerve (parasympathetic)------- motor nerve impulses travel from the spinal cord towards the urinary bladder and the internal sphincter----- as a result ,the urine is transferred from the bladder to the urethra----- presence of urine in the urethra stimulates the stretch receptors of the urethra------generates sensory impulses which travel to the spinal cord------- motor impulses generated from the spinal cord inhibit the pudendal nerve​​------ as a result the external sphincter relaxes and micturition takes place.

Micturition in adults is often a voluntary act. The Pudendal Nerve supplies the external sphincter. It is responsible for the constriction of the external sphincter. Therefore, during micturition,this nerve is inhibited causing the release of urine from the urethra( voiding of urine).