homeostasis and temperature control Flashcards
what is homeostasis
any self-regulating process by which biological systems maintain stability while adjusting to changing external conditions
what controls core body temperature
hypothalamus
what is negative feedback
main mechanism of homeostasis
where body senses change and activates mechanisms that negate or reverses that change
what is positive feedback
self-amplifying cycle
a physical change leads to an even bigger physical change in the same direction
how does lactation work - example of positive feedback
sucking on nipple activates receptors in nipple
signals pituitary gland to produce prolactin and oxytocin
prolactin stimulates milk production
oxytocin promotes smooth muscle contraction allowing milk produced to be ejected out of the nipple
what is thermoregulation
response to internal and external temperature variations
internal variations are detected by thermoreceptors located in the anterior portion of the hypothalamus
how does the hypothalamus thermoregulate
anterior - responds to increases in environmental temperatures and controls the core temperature of the body
posterior - responds to decreases in environmental temperatures
what are the two thyroid hormones and what do they affect
thyroxine (T4)
triiodothryonine (T3)
thermogenic hormones so thermoregulation
what does the sympathetic nervous system do in terms of thermoregulation
activated by flight or fight
leads to increase in catecholamine production
catecholamine binds to beta receptors in brown fat which can generate heat
also activates receptors in vascular smooth muscle of skin blood vessels causing vasoconstriction - reduces heat loss
what happens when the body temperature is high
skin receptors send signals to anterior hypothalamus
anterior hypothalamus increases activity of sympathetic cholinergic fibres which innovate sweat glands leading to sweating
anterior hypothalamus also decreases activity of the SNS in skin blood vessels causing dilation of blood vessels
what is radiation
movement of heat between any 2 objects where the temperature differs
what is conduction
transfer of heat between objects that are in direct contact with each other
what is convection
the transfer of heat by the movement of air or liquid around the body
