Biopsych Prelim 3
Terms
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- set point
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a desired value
-negative feedback works to get body back to the set point when there are deviations from homeostasis - set zone
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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
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urination, heating the body, etc.
we have to always make up for these - ectotherms
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regulate their body temperature through behavioral means
ex_ moving to favoralbe sites or chaning their exposure to external sources of heat. - endotherms
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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
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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
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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
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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 - torpor
- saves a lot of energy for the animal.
- brain regulation of body temperature
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body temperature is regulated in the hypothalamus.
ex) small lesions in dog hypothalamus increased body temperature.
lateral hypothalamus
controls behavioral temperature regulation
POA
-controls autonomic responses to temperature.
-parallel circuits for two ways of regulating the same variable. - extracellular compartment
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water that's outside our cells
broken up into interstitial fluid (fluid between cells) and blood plasma - aquaporins
- proteins that make up specialized water channels that allow water to move back and forth between cells nad in and out of cells.
- osmolality
- the concentration of solute in a solution
- isotonic solution
- has same salt concentration as mammalian fluids have
- hpyertonic
- more salt than mammalian fluids have
- hypotonic
- less salt than mammalian fluids have.
- hypovolemic thirst
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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
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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
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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. - aldosterone
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is crucial to sodium conservation.
aids water retention by acting on the kidneys, inducing them to conserve sodium - glycogon
- form of glucose used for storage
- sequential mechanisms that stimulate insulin release
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1)stimul from food evokes a conditioned rlease of insluin in anticipation of glucoes arrival in the blood.
2) - diabetes mellitus
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real diabetes
type one
-the pancreas stops producing insulin
type two
-insulin insensitivity - Ventromedial hypothalamus lesions
- -produces obesity
- lateral hypothalamus lesions
- anorexia
- leptin
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secreted by fat cells
report how fat the body is - gherlin
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powerful appetite stimulant
one mechanism for obesity might be a gherlin system that is unresponsive to feeding - PYY
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appetite suppressing
increases in concentration after eating - CART and POMC
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inhibit appetite and increase metabolism
both project to the lateral hypothalamus - NPY/AgRP system
- appetite stimulating