Which of the following sequences correctly arranges the stages of hypovolemia/volumetric thirst in the order they occur?

A. Angiotensin II is produced

B. Baroreceptors in the kidneys detect low blood volume

C. Renin is released by the kidneys

D. Thirst sensation is triggered in the hypothalamus

E. Angiotensinogen is converted to angiotensin I

F. Activation of the AV3V (anteroventral third ventricle) region

Choose the correct sequence from the options given below:

The correct answer is B, C, E, A, F, D.

Key Points

• Understanding hypovolemia/volumetric thirst:
  • Hypovolemia refers to a decreased volume of blood in the body, which can trigger volumetric thirst.
  • Volumetric thirst is the body's mechanism to increase fluid intake in response to low blood volume.
• Stages of hypovolemia/volumetric thirst:
  • Baroreceptors in the kidneys detect low blood volume: These receptors sense the decrease in blood volume and trigger the release of hormones to correct this imbalance.
  • Renin is released by the kidneys: In response to low blood volume, the kidneys release renin, an enzyme that plays a crucial role in the regulation of blood pressure and fluid balance.
  • Angiotensinogen is converted to angiotensin I: Renin acts on angiotensinogen, a protein produced by the liver, converting it into angiotensin I.
  • Angiotensin II is produced: Angiotensin I is further converted into angiotensin II, a potent vasoconstrictor that also stimulates thirst.
  • Activation of the AV3V (anteroventral third ventricle) region: Angiotensin II activates the AV3V region in the brain, which is involved in fluid homeostasis and thirst regulation.
  • Thirst sensation is triggered in the hypothalamus: Finally, the hypothalamus is stimulated to create the sensation of thirst, prompting the individual to drink fluids and restore blood volume.

Additional Information

• Incorrect sequences:
  • Option 2: This option incorrectly places the release of renin before the detection of low blood volume by baroreceptors, which is not the correct order of events.
  • Option 3: While it correctly starts with the detection of low blood volume and the release of renin, it incorrectly orders the production of angiotensin II before the conversion of angiotensinogen to angiotensin I.
  • Option 4: This sequence starts with the triggering of thirst sensation, which actually occurs later in the process, making it incorrect.