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21 Cards in this Set

  • Front
  • Back

A variable that is controlled by a regulatory mechanism is called a _____ variable. The optimal value of the aforementioned variable in a regulatory system is called the _____ ______. The _____ is a regulatory mechanism that signals when the first variable deviates from the optimal value. Upon detection of deviance, the _____ mechanism is capable of changing the value of the original variable to achieve homeostasis. _____ ______ terminates the action of the mechanism that changes the value of the variable.

System variable, set point, detector, correctional mechanism, negative feedback.

What is the name of the brain mechanism that causes cessation of hunger or thirst? Why do we need this mechanism?

The Satiety mechanism is needed since drinking and eating is anticipatory, thus we need to inhibit the correctional mechanism to prevent overconsumption since you would keep eating because water and food don't reach their targets immedietly.

What are the 2 major fluid compartments in the body? What are the 4 divisions of the fluid compartments? Arrange them in order of how much water they hold respectively.

Intracellular fluid and Extracellular fluid

Intracellular > Interstitial > Intravascular (blood plasma) > Cerebrospinal fluid

What is the effect of sweating and eating on water intake regulation?

Sweating and eating any meal is dehydrating, increasing fluid intake

What are the 2 types of thirst? What are the stimuli that are the basis of these types of thirst?

1) Cellular dehydration = Osmometric thirst

2) Volume changes = Volumetric/Hypovolemic thirst

Water intake is linked to _____ regulation and ____ intake. What region of the brain is responsible for _____ regulation, and can consequently stimulate thirst?

temperature regulation and food intake. Temp regulation is controlled by the median preoptic nucleus

What are two ways to induce osmometric thirst?

1) Loss of fluid during evaporation

2) Ingestion of salt, increasing tonicity, and inducing movement of water out of cells

What fundamental unit of the kidney regulates fluid levels in the body? What hormones act upon this kidney unit?

Nephrons are acted upon by vasopressin and aldosterone

Water retention and salt retention are modulated by 2 hormones. What are these hormones, and where do they originate in the body? One of these hormones has a behavioral effect, which hormone is it and what is the effect?

Vasopressin from the posterior pituitary increases water retention

Aldosterone from the adrenal cortex increases salt retention and induces salt apetite

Neurons that respond to changes in solute concentrations are what class of receptor? What is the proximate explanation for how these receptors work? How does this regulate axonal activity?

Osmoreceptors lose water and shrink in size when there is increased solute concentration of interstitial fluid. The shrinking is size increases axonal activity.

Receptors that respond to changes in interstitial solute concentration are found where in the brain? What other brain structures respond to this kind of thirst?

Osmoreceptors are found in the anteroventral tip of the 3rd ventricle (AV3V). Anterior cingulate cortex and hypothalamus also activate in response to thirst

Infusion of NaCl into the _____ produces thirst, whereas damage to this area produces lack of thirst

AV3V Antroventral tip of the 3rd ventricle

What 3 stimuli result in reduced blood volume and _______ thirst? This results in what kind of thirst is this called? This thirst promotes water consumption and what else?

Hypovolemic/volumetric thirst is induced by:

1) Blood loss

2) Loss of isotonic fluid due to vomiting diarrhea, digestion etc.

3) Injection of Polyethlyene glycol colloid which sequesters water and salt removing it from the body

Hypovolemic stimuli produce a salt appetite

What cells detect the presence of hypovolemia? How do these cells detect hypovolemia? What enzymes and hormones are released when this condition is detected?

Kidney cells detect hypovolemia as reduced blood flow

Baroreceptors in the atrium of the heart detect hypovolemia by decreased intravascular volume

Kidney cells secrete renin enzyme into the blood where is catalyzes the conversion of angiotensinogen --> angiotensin 1 which quickly is converted to angiotensin 2 (active form)

How does the body reinstate homeostasis upon detection of hypovolemia?

The kidneys secrete renin which ultimately makes angiotensin II

Hypovolemia causes the release of what 2 hormones? These hormones exert what 3 physiological effects and 2 behavioral effects does the body modulate to reinstate homeostasis upon detection of hypovolemia?

Angiotensin II stimulates secretion of vasopressin and aldosterone subsequently causing:


1) Retention of sodium

2) Retention of water

3) Contraction of blood vessels


1) Water seeking behavior

2) Salt seeking behavior

Arterial baroreceptors' signals terminate in the ______ _____ nucleus of the anterior hypothalamus. What is the pathway from the baroreceptor to the anterior hypothalamic nuclei?

Median Preoptic nucleus

Baroreceptor --> Nucleus of the solitary tract (NST) --> Anteroventral tip of the 3rd ventricle (AV3V) --> Median Preoptic Nucleus

The _____ _____ nucleus of the anterior hypothalamus and the _________ organ of the fornix are both involved in mediation of hypovolemic thirst. Arterial baroreceptors's information and Angiotensin II act on which site respectively?

Median preoptic nucleus - arterial baroreceptors

Subfornical organ - Angiotensin II

Angiotensin II can stimulate drinking, but lesions of a region in the telencephalon can abolish angiotensin II's action. What region is this?

Lesions of the subfornical organ abolish angiotensin II induced drinking

Angiotension II's site of action projects to what area of the brain?

What system does this site belong to and what is unique about it?

What other paths terminate at this site in the regulation of body fluids?

The subfornical organ is the site of action of angiotensin II and is located outside the blood-brain barrier part of the circumventricular system.

The subfornical organs projects to the median preoptic nucleus

Information from arterial baroreceptors also projects here.

Osmotic thirst and volumetric thirst is regulated by projections that terminate in the _____ _____ nucleus of the anterior hypothalamus to promote drinking. What are the 2 inputs to this area that are found outside the blood brain barrier? What is the 3rd input to this system?

3rd input = Median preoptic nucleus is acted upon by the arterial baroreceptors via the nucleus of the solitary tract.

It is also acted upon by the subfornical organ and the osmoreceptos of AV3V, all of which are outside the BBB