homeostasis Flashcards
what is homeostasis
maintenance of constant internal environment within tolerable limits
what are components of homeostatic control
norm, stimulus, receptor, control centre, corrective mechanism, negative feedback
why is homeostasis needed (physiological)
optimal functioning of physiological processes as well as component cells, tissues, organs, organ systems
why is homeostasis needed (external and internal environment)
achieve a certain degree of independence from external environment so that internal environment is maintained in an optimal condition and a state of maximum efficiency.
why is negative feedback to control centre via receptor needed
stop corrective mechanism when norm is reached
for body temperature negative feedback mechanism, what is stimulus (for internal and external temp.)
Increase beyond norm: drink hot soup, vigorous exercise (I), hot day(E)
Decrease beyond norm: cold food(I), cold day(E)
receptor for body temp. negative feedback mechanism and how they detect temp. for both internal and external temp. changes
THERMORECEPTORS in hypothalamus detect internal temp. change by monitoring temp. of blood flowing through it
THERMORECPTORS on skin detect external temperature changes
what is control centre ie. where are the nerve impulses sent to from receptor
hypothalamus
what function of hypothalamus after receiving nerve impulses
send nerve impulses to effector
corrective action carried out by arterioles in skin when change in temp (+/-)
vasodilation of arterioles in skin, more blood flow into capillaries near skin surface, so more heat lost to surroundings by conduction, convection, radiation
vasoconstriction of arterioles, less blood flow into capillaries near skin surface, less heat lost to surroundings by conduction, convection, radiation
corrective action carried out by liver when change in temp (+/-)
metabolic rate decrease, less heat released
metabolic rate increase, more heat released
corrective action by skeletal muscles for (-)
skeletal muscles undergo spasmodic contraction -> release heat due to muscle respiration, release energy for contractions, not effective for long periods of time
corrective action carried out by erector muscle when change in temp (+/-)
relax, hair shaft flatten, more circulation of air over hairs, moving air conducts heat away from body
contracts, hair shaft perpendicular to skin surface, trap air. trap air is poor conductor of heat, heat retained, keep skin warm
corrective action carried out by arterioles in sweat glands when change in temp (+/-)
sweat glands more active, more sweat produced, water in sweat evaporated, remove latent heat of vapourisation from body
sweat glands less active, less sweat produced, sweat comparatively dry, no evaporation no cooling effect
what happens after corrective action
body temp increase/decrease back to norm. negative feedback sent to the control centre via receptor to stop further corrective action
