Chapter 12: DRINKING

Question 1

4 essential features of regulatory mechanisms?

Answer 1

• system variable: characteristics to be regulated
• set point: optimal value of system variable
• detector: monitors value of system variable
• correctional mechanism: restores system variable to set point

Question 2

What are regulatory systems regulated by?

Answer 2

negative feedback: effect produced by an action that diminishes or terminates that action

Question 3

What are ingestive behaviours controlled by?

Answer 3

• satiety mechanism

- causes cessation of hunger or thirst produced by adequate available supplies of nutrients or water.

Question 4

How much of body fluid is intracellular?

Answer 4

67%

Question 5

3 type of extracellular fluid?

Answer 5

• interstitial
• blood plasma (intravascular fluid)
• CSF

Question 6

percentage of interstitial fluid?

Answer 6

26%

Question 7

percentage of intravascular fluid?

Answer 7

7%

Question 8

percentage of CSF?

Answer 8

less than 1%

Question 9

What is hypovolemia?

Answer 9

Reduction in the volume of the intravascular fluid

Question 10

How can the vascular system of body make some adjustments for loss of blood volume?

Answer 10

-contraction of muscles in smaller veins and arteries

Question 11

What is water loss mostly caused by?

Answer 11

• evaporation

- sweating (also decreases sodium so both needs)

Question 12

Different steps of thirst

Answer 12

• water is lost through evaporation
• concentration of interstitial fluid increases
• capillaries lose water by osmosis
• cells lose water by osmosis

Question 13

osmometric thirst?

Answer 13

• solute concentration of the interstitial fluid increases
• water drawn out of cells, shrink in volume.
• osmoreceptors respond to changes in fluid concentration

Question 14

What are osmoreceptors?

Answer 14

• neurons whose firing rate is affected by their level of hydration.
• detect changes in the solute concentration of the interstitial fluid that surrounds it

Question 15

Where are osmoreceptors responsible for osmometric thirst located?

Answer 15

-lamina terminalis

Question 16

What part of the brain does sensation of thirst involve?

Answer 16

• ACC: Anterior Cingulate Cortex

- injection of saline in ACC produces thirst, which is then relieved by drinking

Question 17

Volumetric thirst?

Answer 17

• produced by hypovolemia

- blood loss= most obvious cause

Question 18

How do detector cells induce volumetric thirst?

Answer 18

• detector cells in the heart and kidneys help monitor blood volume
• when volume is low, induces volumetric thirst

Question 19

What is angiotensin?

Answer 19

• peptide hormone
• constricts blood vessels
• causes retention of sodium and water
• produces thirst and a salt appetite
• kidneys are responsible for its presence

Question 20

What type of detector cells are located in the heart?

Answer 20

-baroreceptors