Question

What are the Mechanisms of micturition and defecation reflexes?

Answer 1

Micturition reflex:

The micturition reflex consists of following processes,

1) the stretch receptors present in the walls of the urinary bladder since the bladder feeling and transmit the impulses to the spinal cord.

2) the s2 and s3 segments of spinal cord act as the coordinating centre and transmit the impulses back to the urinary bladder through parasympathetic nerves present in the pelvic nerve

3) the efferent signals contract the detrusor muscle and relaxes the internal sphincter. As a result, urine is voided involuntarily if not inhibited by the brain.

4) the voluntary control of micturition is present in the pons of brain

Defecation reflex:

The defecation reflex consists of the following processes,

1) when the faeces reache the rectum, it stimulates the stretch receptors present in the walls of the rectum

2) the afferent impulses reach the the spinal cord and the afferent impulses travel through parasympathetic nerves

3) the efferent impulse cause contraction of rectum and sigmoid colon and relaxation of internal anal sphincter resulting in voiding of faeces