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Biopsych Prelim 3


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set point
a desired value

-negative feedback works to get body back to the set point when there are deviations from homeostasis
set zone
for most systems, there is really a set zone that the system can be in

without some tolerance, the system would be going on and off very frequently.
obligatory losses
urination, heating the body, etc.

we have to always make up for these
regulate their body temperature through behavioral means

ex_ moving to favoralbe sites or chaning their exposure to external sources of heat.
primarily regulate body temperature by making internal adjustments

regulate their body temp chiefly by internal metabolic processes

-generate heat through metabolism.
advantages and disadvantages of endothermy
advantage--greater independence from environmental conditions

advantage---in order to fuel chemical reactions in the body through which they generate heat, endotherms evolved a greater capacity for oxygen utilization.. allows us to sustain high levels of muscle activity over longer periods of time
disadvantage--requires a lot of energy.
brown fat
found around vital organs in the trunk

full of mitochondria.

break down molecules and produce heat.

under cold conditions, the sympathetic nervous system stimulates the metablolism within brown fat cells, producing heat.
behavioral thermoregulatory responses of ectotherms and endotherms
1) changing exposure of the body surface
ex) huddling

2) changing external insulation
ex) using clothing or nests

3) selecting a surrounding that is less thermally stressful
ex) going to the shade
saves a lot of energy for the animal.
brain regulation of body temperature
body temperature is regulated in the hypothalamus.

ex) small lesions in dog hypothalamus increased body temperature.

lateral hypothalamus
controls behavioral temperature regulation

-controls autonomic responses to temperature.

-parallel circuits for two ways of regulating the same variable.
extracellular compartment
water that's outside our cells

broken up into interstitial fluid (fluid between cells) and blood plasma
proteins that make up specialized water channels that allow water to move back and forth between cells nad in and out of cells.
the concentration of solute in a solution
isotonic solution
has same salt concentration as mammalian fluids have
more salt than mammalian fluids have
less salt than mammalian fluids have.
hypovolemic thirst
low extracellular volumes of water

triggered by the loss of blood or other body fluids

extracellular fluid is depleted w/o changes in solute concentration.

no osmotic pressure to push water from one compartment to another

causes release of vasopressin (ADH) to reduce urination and constrict blood vessels.

renin and angiotensin are also released to conserve water.
osmotic thirst
high extracellular solut concentration.

total volume of water is constant, but a sudden increas in the amount of solute in the extracellular comparrtment exerts osmotic pressure that pulls water out of the intracellular compartment.

how thirst is most commonly produced.

obligatory water losses where more water is lost than salt messes up the concentrations of fluids.

some hypothalamic cells might be osmosensory neurosn--cells that respond to changes in osmotic pressure
diabetes insipidus
the production of vasopressin ceases, and the kidneys retain less water.

they send more urine to the bladder, and that urine is very pail and dilute.

chronic thirst.
is crucial to sodium conservation.

aids water retention by acting on the kidneys, inducing them to conserve sodium
form of glucose used for storage
sequential mechanisms that stimulate insulin release
1)stimul from food evokes a conditioned rlease of insluin in anticipation of glucoes arrival in the blood.

diabetes mellitus
real diabetes

type one
-the pancreas stops producing insulin

type two
-insulin insensitivity
Ventromedial hypothalamus lesions
-produces obesity
lateral hypothalamus lesions
secreted by fat cells

report how fat the body is
powerful appetite stimulant

one mechanism for obesity might be a gherlin system that is unresponsive to feeding
appetite suppressing

increases in concentration after eating
inhibit appetite and increase metabolism

both project to the lateral hypothalamus
NPY/AgRP system
appetite stimulating

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