Homeostasis Flashcards
What is homeostasis
Homeostasis is the bodies way of regulating internal factors to keep them constant
what is negative feedback
When the body counteracts any internal changes so that it stays at its optimum conditions
What is needed for negative feedback
-Sensory receptors (detect
changes in internal
conditions)
-Effectors (provide response)
what is positive feedback
opposite of negative feedback (increases change so that the conditions are further from the optimum)
What is an ectotherm?
An ectotherm is an organism which regulates its body temperature with the help of external
source
What are endotherms?
organisms that control internal temperatures through respiration and are independent of external temperature
What are some responses to restore optimum temp
Shivering – contractions of skeletal muscles stimulated by nerve impulses sent out
by the hypothalamus, lead to increase in temperature as heat is released
* Sweat glands – sweat production to decrease body temperature via evaporation
* Hairs on skin – lie flat to minimise insulation and increase heat loss, raised to provide
insulation and reduce heat loss
* Arterioles – dilate to increase heat loss as blood flows closer to skin, constrict to
reduce blood flow and therefore minimise heat loss
What are receptors?
receptors detect stimuli
are specific-only detect certain stimulus
some are cells and some are protein
What are effectors
cells that bring about a response to a stimulus
What is cell signalling
way of communication between cells
can occur between adjacent cells
or distant cells
What are the mechanisms that reduce body temp
Sweating
Hairs lie flat
Vasodilation
What are the mechanisms that increase body temp
shivering
Much less sweat
Hairs stand up
vasoconstriction
hormones
How does sweating reduce body temp
water ins sweat evaporates from surface of skin and takes heat from body. As a result the skin is cooled
How does hair lying flat reduce body temp
less air is trapped
skin is less insulated
heat can be lost easily
How does vasodilation reduce body temp
arterioles near skin dilate
More blood flows through the capillaries in the surface layer of dermis
more heat loss from skin by radiation
temp is lowered
How does shivering increase body temp
Muscles contract in spasms
more heat is produced from increased respiration
How does sweating less increase body temp
Less sweat is secreted from sweat glands when its cold
reducing the amount of water evaporated
therefore reducing heat loss
How do hairs standing up increase body temp
erector pili muscles contract when it is cold
makes hairs stand up
this creates insulating layer
that traps more air so reduces heat loss
How does vasoconstriction increase body temp
Arterioles constrict
less blood flows through capillaries
less heat loss
What happens when body temp increases from the optimum (37)
Thermoreceptors detect temp change
hypothalamus sends signals to effectors
-sweating
-hairs lie flat
-vasodilation
-etc.
More heat lot and less heat produced by body
How does a beta cell release insulin
When blood glucose conc is high
glucose enters Beta cells via facilitated diffusion
rate of respiration increases making more ATP
causes potassium ion channels to close
potassium builds up inside the cell
plasma membrane of beta cell is depolarised
ca channels open
vesicles fuse with beta cell memrbane t release insulin
