PSYC 211 Study Guide - Final Guide: Posterior Pituitary, Lamina Terminalis, Osmoreceptor

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26 Jun 2012
PSYC 211 FINAL NOTES 4/19/2012 12:30:00 PM
Regulation of fluid that bathes our cells homeostasis
Ingestive behavior: intake of food, water and minerals such as sodium.
A regulatory mechanism contains four essential features: the system
variable (characteristic to be regulated), a set point (the optimal value of the
system variable), a detector that monitors the value of the system variable,
and a correctional mechanism that restores the system variable to the set
When a sufficient amount of drinking occurs, the satiety mechs stop further
drinking in anticipation of the replenishment that will occur later.
The body contains four major fluid compartments: one
compartment of intracellular fluid (2/3 of body’s fluid) and three of
extracellular fluid (intravascular fluid blood plasma, CSF,
interstitial fluid isotonic with intracellular fluid)
o If interstitial fluid loses water (hypertonic) and water pulled
out of cells
Hypovolemia low volume of blood (loss of blood, vomiting and
diarrhea) adjustments for loss of blood volume by contracting the
muscles in smaller veins and arteries, thereby presenting a smaller
space for the blood to full, but this correctional mech has definite
Thirst osmometric and volumetric moisture lost through
evaporation is pure distilled water.
Osmometric thirst is when solute concentration of interstitial fluid
increases. Detectors = osmoreceptors and firing rate affected by
level of hydration located in lamina terminalis which has two
circumventricular organs OVLT and SFO and are located outside
BB barrier
o Eating salty meal pure osmometric thirst
o Thirsty subjects had activity in ACC and lamia terminalis but
when allowed to drink, activity decreased only in ACC
therefore ACC reflects thirst
o Evaporation produces both osmometric and volumetric thirst
Volumetric thirst kidneys detect decreases in flow of blood to
them when decreased, cells in there secrete renin which enters
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blood and catalyzes conversion of angiotensinogen into angiotensin
active form = AII stimulates secretion of hormones by posterior
pituitary and adrenal cortex causing kidneys to conserve water and
sodium and increased blood pressure through constriction of
arteries initiates both drinking and salt appetite
o Hypertension (high blood pressure) caused by oversecretion
of renin Captopril blocks enzyme that converts AI to AII
o Aldosterone, steroid hormone, that stimulates kidneys to
retain sodium
o Atria passively filled with blood being returned from the body
by the veins. When the volume of the blood plasma falls, the
atria become less full and the stretch receptors within them
will detect this change
Neural Mechs of Thirst
o Sensory info from baroreceptors in atria sent to nucleus of
the solitary tract sends efferent axons to lamina terminalis
o Subfornical organ is site at which blood angiotensin acts to
produce thirst very low doses of angiotensin injected into
SFO cause drinking
o Neurons in subfornical organ send axons to median preoptic
nucleus (in lamina terminalis) which acts as an integrating
system for most or all of the stimuli for osmometric and
volumetric thirst.
o Adipsia lack of drinking
Short term carbohydrates liver - glycogen; long term reservoir -
fats (triglycerides) beneath skin in adipose tissue
Liver glucose to glycogen in presence of insulin
o Fall in glucose stops secretion of insulin and starts secreting
o Reserved primarily for CNS where it is absorbed and
metabolized by neurons and glia
Adipose tissue cells capable of absorbing nutrients from blood and
converting to triglycerides for storage sympathetic nervous
system for breakdown (which decreases parasymp NS activity)
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