Chapter 12: DRINKING Flashcards
4 essential features of regulatory mechanisms?
- 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
What are regulatory systems regulated by?
negative feedback: effect produced by an action that diminishes or terminates that action
What are ingestive behaviours controlled by?
- satiety mechanism
- causes cessation of hunger or thirst produced by adequate available supplies of nutrients or water.
How much of body fluid is intracellular?
67%
3 type of extracellular fluid?
- interstitial
- blood plasma (intravascular fluid)
- CSF
percentage of interstitial fluid?
26%
percentage of intravascular fluid?
7%
percentage of CSF?
less than 1%
What is hypovolemia?
Reduction in the volume of the intravascular fluid
How can the vascular system of body make some adjustments for loss of blood volume?
-contraction of muscles in smaller veins and arteries
What is water loss mostly caused by?
- evaporation
- sweating (also decreases sodium so both needs)
Different steps of thirst
- water is lost through evaporation
- concentration of interstitial fluid increases
- capillaries lose water by osmosis
- cells lose water by osmosis
osmometric thirst?
- solute concentration of the interstitial fluid increases
- water drawn out of cells, shrink in volume.
- osmoreceptors respond to changes in fluid concentration
What are osmoreceptors?
- neurons whose firing rate is affected by their level of hydration.
- detect changes in the solute concentration of the interstitial fluid that surrounds it
Where are osmoreceptors responsible for osmometric thirst located?
-lamina terminalis
