Chapter 10 - Temperature, Thirst and Hunger Flashcards
homeostasis
regulation of temperature and other biological processes that keep body within fixed range
set point
a single value that the body works to maintain
negative feedback
processes that reduce discrepancies from the set point
allostasis
the adaptive way the body changes its set points depending on the situation
how does allostasis differ from homeostasis
homeostasis is keeping the body within a set point, allostasis shifts the body’s set point depending on situation
basal metabolism
the energy used to maintain a constant body temperature while at rest (2/3 of our total energy)
poikilothermic
“cold blooded” - body temperature matches environmental temperature
what kinds of animals are poikilothermic?
amphibians, reptiles and most fish (except sharks and large fish like tuna)
homeothermic
“warm blooded” - body temperature is regulated by physiological mechanisms
what kinds of animals are homeothermic?
mammals and birds
how do animals cool their bodies physiologically?
evaporation. by sweat (i.e humans) or by licking and panting if the species doesnt sweat (i.e. dogs)
how do animals increase body heat?
shivering (muscle contractions generate heat) or decreased blood flow to the skin (stops blood from cooling too much). nonhumans fluff fur to increase insulation
why dont our bodies temperature increase past 37 C/98 F?
1) requires more fuel/energy. 2) beyond 40C, proteins break bonds and lose properties
do reproductive cells require cooler or warmer environments?
cooler (hence men’s scrotums hanging outside the body, and eggs being sat on instead of kept inside the too hot bird)
which structure(s) in the brain regulate(s) temperature?
POA/AH - the anterior hypothalamus and preoptic area
POA/AH
hpreoptic area / anterior hypothalamus
how does the POA/AH regulate body temperature?
by monitoring its own temperature. if it is heated, the animal will pant or sweat, if it is cooled, it will shiver. even in a room of opposite temperature.
how can an animal regulate body temperature after damage to the POA/AH?
by behavioral mechanisms like seeking warmer or cooler locations
cause of fever
bacterial and viral infections
reason of fever
to inhibit bacterial growth and increase survivability after infection
cytokines
leukocytes->release cytokines->stimulate vagus nerve->signals hypothalamus->release of prostaglandins (necessary for fever)
how high is too high of a fever?
39C (103F). 41C(109F) is life threatening
water constitutes what percent of the mammalian body?
70%
vasopressin
hormone released by posterior pituitary that raises blood pressure by constricting blood vessels. compensates for decreased blood volume when dehydrated. enables idneys to reabsorb water from urine
antidiuretic hormone
vasopressin
if you lacked vasopressin would you drink more or less?
more. you would excrete more water and would need to replace it
osmotic pressure
tendency of water to flow from low concentration to high concentration across membranes
increase of sodium causes osmotic or hypovolemic thirst?
osmotic
osmotic thirst
thirst triggered by cells when concentration of solutes is higher within the membrane
OVLT & SFO
areas important for monitoring osmotic pressure & salt content of the blood
supraoptic nucleus & paraventricular nucleus (PVN)
control the rate vasopressin is released
lateral preoptic area
help control drinking along with hypothalamus
angiotension II
constricts blood vessels like vasporessin, due to drop in blood pressure due to bleeding, diarrhea or sweating. (low volume)
hypovolemic thirst
thirst triggered by loss of salt AND water due to bleeding, diarrhea, or sweating (low volume)
sodium-specific hunger
preference for salty tastes when hypovolemic thirst is present
aldosterone
hormone which causes kidneys, salivary & sweat glands to retain salt when sodium reserve is low (low sodium)
who would drink more pure water? someone with osmotic or hypovolemic thirst?
osmotic thirst.
who would drink more salt water? someone with osmotic or hypovolemic thirst?
hypovolemic thirst
lactase
enzyme necessary for metabolizing lactose
lactose
the main sugar in milk
tryptophan is increased by…? and increases…?
increased by carbohydrates…. increases sleepiness by triggering release of melatonin
vagus nerve
conveys information about stretching of stomach walls, providing basis for satiation
splanchic nerves
convey information about nutrient contents of stomach
cholecytokinin (CCK)
hormone which limits meal size by constricting th sphincter (facilitating distention), signals vagus nerve to release CCK-like neurotransmitter to the brain
