Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Micturition is the process of release of urine from the urinary bladder, initiated by a neural mechanism called the micturition reflex.
As the urinary bladder fills with urine, its muscular walls are stretched, activating stretch receptors located on the bladder wall.
The stretch receptors send signals to the Central Nervous System (CNS), which in turn sends motor messages to initiate the contraction of the smooth muscles of the bladder and simultaneous relaxation of the urethral sphincter.
Adult humans excrete, on average, to liters of urine per day.
Urine is a light yellow colored, watery fluid which is slightly acidic, with an average , and has a characteristic odor.
On average, g of urea is excreted out via urine per day.
Various conditions can affect the characteristics of urine; for example, the presence of glucose (Glycosuria) and ketone bodies (Ketonuria) in urine are indicative of Diabetes Mellitus.
📐Formulae
💡Examples
Problem 1:
What would be the effect on micturition if the stretch receptors on the urinary bladder wall were completely removed or non-functional?
Solution:
Micturition will not occur in a regulated manner.
Explanation:
The micturition reflex is initiated by stretch receptors. If these are removed, the CNS will not receive the signal that the bladder is full, meaning the contraction of the bladder muscles and relaxation of the sphincter will not be triggered normally.
Problem 2:
Calculate the approximate concentration of urea in urine (in g/L) if an individual excretes L of urine containing g of urea.
Solution:
Explanation:
The concentration is found by dividing the total mass of urea by the total volume of urine excreted.