Correct option is A
Detailed Explanation:
Let's evaluate each of the statements and how they correspond to the mechanisms of thirst regulation:
Statement A: Hypertonicity leads to osmoreceptor activation giving rise to hypothalamic control of thirst.
- Correct: Hypertonicity (increased plasma osmolarity) triggers the activation of osmoreceptors in the hypothalamus, which in turn stimulates the feeling of thirst. This pathway is one of the primary mechanisms that regulates thirst in response to increased plasma osmolarity.
Statement B: Hypertonicity leads to baroreceptor activation giving rise to hypothalamic control of thirst.
- Incorrect: Baroreceptors are more sensitive to changes in blood volume (hypovolemia) rather than osmolarity. They detect low blood pressure or decreased blood volume, which activates thirst through different pathways, such as the release of angiotensin II. Hypertonicity mainly activates osmoreceptors, not baroreceptors, for thirst regulation.
Statement C: Hypovolemia leads to activation of baroreceptor and angiotensin II giving rise to hypothalamic control of thirst.
- Correct: Hypovolemia (reduced blood volume) activates baroreceptors, which send signals to the brain to increase thirst. Additionally, angiotensin II, which is produced in response to low blood volume, also stimulates thirst by acting on the hypothalamus. This pathway is key in regulating thirst in response to blood volume loss.
Statement D: Hypovolemia leads to osmoreceptor activation giving rise to hypothalamic control of thirst.
- Incorrect: Osmoreceptors primarily detect changes in osmolarity (concentration of solutes) and are activated by hypertonicity, not hypovolemia. While hypovolemia affects thirst, it does so through baroreceptors and angiotensin II, not through osmoreceptors.
Conclusion:
The correct combination of true statements is A and C:
- Statement A: Hypertonicity activates osmoreceptors for thirst control.
- Statement C: Hypovolemia activates baroreceptors and angiotensin II to regulate thirst.
