B 13.2 - Homeostasis Flashcards
3 internal conditions that are kept constant
-body temperature
-blood glucose concentration
-water potential of the blood
internal environment
whats going on inside an organism (outside of cells)
external environment
whats going on outside an organism’s body (surroundings)
why does the internal environment need to be kept constant?
so cells can work efficiently
what is homeostasis?
maintenance of a constant internal environment
how do mammals maintain a constant internal body temperature?
-insulation
-sweating
-shivering
-vasodilation of arterioles
-vasoconstriction of arterioles
what are cells in blood surrounded by?
plasma
what are other cells surrounded by?
tissue fluid
where are the optimum conditions for the internal environment maintained within?
plasma and tissue fluid
how is homeostasis brought about?
(homeostatic control)
negative feedback:
-sensory receptors send body information to brain continuously
-if level is beyond the normal range, brain initiates a response to bring level back to within set points
-receptors inform brain that the level has been restored
what is negative feedback
detect
–>change from set point
correct
–>triggers response that brings level back to its set point
effect in cells of blood glucose levels are being too high?
cells lose water due to osmosis
–>outside has lower water potential (high concentration of glucose)
–> cell shrivels up / gets crenated
effect of blood glucose levels being too low for cells?
-cells cant respire, can’t release energy needed
-brain cells die quickly
how does glucose get into blood?
-starch broken down into glucose by enzymes (in mouth and duodenum)
-gets absorbed out of small intestines into blood
why is glucose needed when you exercise?
-muscles need to contract more
-more energy is needed
-more respiration needs to happen
-more oxygen + glucose needed
role of pancreas in controlling blood glucose levels
-detects blood glucose levels
-secretes insulin and glucagon
process of homeostasis if blood glucose levels are too high
-detected by pancreas
-insulin is released into blood
-insulin decreases blood glucose levels by:
–>causing cells to take up more glucose for respiration
–>causing glucose to turn into glycogen in liver cells
why does glycogen not affect blood glucose levels?
it’s insoluble so it doesn’t affect osmosis (water potential of cytoplasm or blood)
process of homeostasis if blood glucose levels are too low
-pancreas detects blood glucose levels
-glucagon is released into blood
-glucagon increases blood glucose levels by:
–>making liver change glycogen to glucose
why should body temperature be kept constant? (enzymes)
enzymes work best at optimum temperatures (gets denatured if temperature is too high)
why should body temperature be kept constant? (cell membranes)
membranes become more fragile as temperature increases
why should body temperature be kept constant? (diffusion rates)
rates increase at a higher temperature and decrease at a lower temperature
-affects gas exchange and absorption
why should body temperature be kept constant? (liquids like blood)
liquids become more viscous (thick and sticky, no flow) as temperature decreases
how does the body gain heat? specific examples as well
-metabolism (respiration, chemical reactions in the liver)
-movement (respiration, friction within muscles)
how does the body lose heat? reason why? specific examples?
-urine & faeces (when expelled from body, heat is lost)
-evaporation of water (when water evaporates, it takes heat with it
–>sweat on skin
–>exhaled air
how does the body retain heat?
apidose (fat) tissue under the skin
what do sensory receptors in skin detect?
external temperature
what do sensory receptors in brain detect?
internal temperature (blood)
4 effectors that control body temperature
-sweat glands
-skeletal muscle
-muscles in wall of skin arterioles
-erector muscles
4 ways heat is lost
-evaporation
-radiation
-conduction
-convection
what is evaporation
loss of heat by evaporation of water (sweat)
what is radiation
emission of electromagnetic radiation
what is conduction
direct transfer by contact
what is convection
moving air removes radiated heat
4 responses to the body being too cold
–retain heat loss
-hairs stand on end
-sweat glands stop making sweat
-shivering
-vascoconstriction
hairs standing on end
-effector?
-how it works
-hair erector muscles contract
-warm still air is trapped that acts as an insulator (convection)
–> less heat lost by radiation
shivering
-effector?
-how it works
-skeletal muscles
-muscles repeatedly contract, generating heat
vascoconstriction
-effector?
-how it works
-muscles in wall of skin arterioles
–skin arterioles (blood vessels near skin surface) constrict (get narrow)
–shunt vessels dilate (get wide)
–less blood flows to the skin –> decreases heat loss (from skin surface to the environment) by radiation
3 responses if the body is too hot
-hairs lie flat
-sweating
-vascodilation
hairs lie flat
-effector?
-how it works
-hair erector muscles relax
-no trapped air –> convection increases –> heat lost by radiation
sweating
-effector?
-how it works
-sweat glands make sweat
-sweat released onto skin surface –> sweat evaporates –> heat is lost when sweat evaporates
vascodilation
-effector?
-how it works
-muscles in wall of skin arteriole
–skin arterioles (blood vessels near skin surface) dilate (get wide)
–shunt vessel constrict (get narrow)
–more blood flows to skin –> increases heat loss (from skin surface to the environment) by radiation
