Question

1. Describe the process of urination or micturition.

2. What is renal clearance? How do the values of renal clearance indicate absorption, secretion, or neither of a substance?

3. Name the 3 systems used to regulate pH.

Answer 1

1. The process of Urination or micturition involves all these steps-

It is a parasympathetic control.

Bladder sends signals through the spinal cord and activate the pontine micturition centre and cerebrum.

When there is a voluntary decision to urinate neurons of pontine micturition centre fire an impulse and excite the sacral preganglionic neurons.

This stimulates the Pelvic Nerve causes a release of acetylcholine.

This activates M3 muscarinic ACh receptors on the detrusor muscle.

This contracts the bladder.

Pontine micturition inhibits Onuf's nucleus, this stimulates internal urethral sphincter causing relaxation.

This contracts the external urethral sphincter voluntarily and allows the distention of urethra and passing of the urine.

2. Renal clearance of a substance is the volume of plasma that would have to be filtered by the glomerulus each minute to account for the amount of that substance appearing in the urine each minute. The formula of renal clearance is

ClX = (UX) • (V)/ PX; where UX is the concentration of drug X in the urine (mg/ml), V is the urine flow rate (ml/min), and PX is the concentration of drug X in the plasma (mg/ml).

3. The three systems used to regulate the pH are

1. Respiratory System
2. Circulatory System
3. Excretory System