Describe the stimuli that induce volumetric thirst. What will ...

[Alainaaa8]

Describe the stimuli that induce volumetric thirst.
 
  What will be an ideal response?

Question 2

Contrast the roles of ghrelin and of cholecystokinin (CCK) for the control of eating.
 
  What will be an ideal response?

[tdewitt]

Answer to Question 1

Answer: Two sets of detectors initiate volumetric thirst. The first are detectors within the kidney that are sensitive to blood flow. Upon activation, these cells secrete renin, which starts a sequence of catalytic events relating to angiotensin, which in turn initiates drinking and consumption of salt. The second set of detectors is located within the atria; these detectors are sensitive to stretching of the atrial walls. These receptors report reduced atrial pressure to the brain, which initiates drinking. Evaporation will reduce the plasma compartment, leading to volumetric thirst. Other volumetric stimuli are loss of blood, vomiting, or diarrhea.

Answer to Question 2

Answer: Ghrelin is released from the stomach when it and the duodenum are empty of food. Injection of ghrelin stimulates eating, while food intake suppresses ghrelin levels. CCK is released into blood upon the entry of fats into the duodenum. CCK is thus in a position to provide a satiety cue to the brain. Injection of CCK reduces eating in the short-term. Obesity is noted in rats for which a genetic mutation impairs the production of CCK receptors.