Question

If nephrons are always producing urine, what causes the urge to use the bathroom?

a. The bladder sends pain messages to the brain (stretch receptors) when full.
b. Active transport of urine by nephrons.
c. Hormonal signals from the kidneys.
d. Neural impulses from the urethra.

Answer 1

The urge to urinate is triggered by stretch receptors in the bladder as it fills with urine, causing bladder pressure to rise and initiating the micturition reflex that leads to urination.

Step-by-step explanation:

The urge to use the bathroom is caused when the bladder becomes full and the stretch receptors in the bladder wall send sensory nerve signals to the brain, indicating it is time to urinate. These receptors are sensitive to the increase in bladder pressure, which rises steadily as the bladder fills. Eventually, this pressure reaches a threshold that triggers the micturition reflex, intensifying the sensation that one needs to urinate. This reflex involves the contraction of the detrusor muscle and the relaxation of the internal urethral sphincter, allowing urine to flow from the bladder into the urethra and then out of the body. The process of urination is under conscious control, meaning we can choose when to relax the external urethral sphincter to release urine.