Homeostasis: Feedback Loops Flashcards
low core body temperature
low body temp. > cold thermoreceptors in skin/hypothalamus > thermoregulatory centre in hypothalamus > arrector pili muscles/arterioles in skin/skeletal muscles/thyroxine/TSH/thyroid gland/adrenaline > piloerection/vasoconstriction/shivering/metabolims increases > body temp. is raised
CO2 after exercise
low CO2 levels in blood > chemoreceptors in the aortic and carotid bodies/MO > resp. centre > resp. muscles > decreased rate/depth of breathing > CO2 levels return to normal
high core body temp.
high body temp. > heat thermoreceptors in skin/hypothalamus > thermoregulatory centre in hypothalamus > muscles/arterioles in skin/sweat glands > peripheral vasodilation/sweating > body temp. is lowered
low blood glucose levels (glycogenolysis)
low blood glucose (<90mg/100ml) > alpha cells of IOL of pancreas > alpha cells secrete glucagon > liver/muscle cells > glycogenolysis > blood glucose levels increase
low external body temp.
low body temp. > cold thermoreceptors in skin > cerebral cortex > body muscles > put on more clothes/increase activity levels/huddle/actively seek warmth etc. > body temp. is raised
high external body temp.
high body temp. > heat thermoreceptors in skin > cerebral cortex > body muscles > seek shade/remove clothing/pour water etc. > body temp. is lowered
reabsorption of salt under influence of aldosterone
decreased blood volume/lower blood pressure > baroreceptors in renal artery > aldosterone from adrenal cortex > sodium pumps in DCT/LOH > sodium is reabsorbed > creation of an osmotic gradient
CO2 during exercise
high CO2 levels/low pH/high H+ > chemoreceptors in the aortic and carotid bodies/medulla oblongata > respiratory centre in the MO > resp. muscles > increased rate/depth of breathing > CO2 levels return to normal
high blood glucose levels (glycogenesis)
high blood glucose (>90mg/100ml) > beta cells of IOL of pancreas > beta cells secrete insulin > liver/muscle cells > gylcogenesis/increased sugar uptake by cells/lipogenesis > blood glucose levels decrease
‘fight or flight’ response
normal blood glucose levels > various receptors (chemoreceptors/baroreceptors/nociceptors) > CNS-adrenal medulla-adrenalin > liver/muscle cells > gycogenolysis > blood glucose levels increase
structure of a negative feedback loop
stimulus > receptor > control centre/medulla > effector > response > feedback
reabsorption of water under influence of ADH
decreased blood volume/lower blood pressure/increased osmotic pressure > osmoreceptors in hypothalamus > hypothalamus causes release of ADH from posterior pituitary gland > DCT/collecting duct > increases permeability of DCT/collecting duct > water reabsorbed/osmotic pressure reduced
stretch receptors in breathing
increased lung volume > stretch receptors > resp. centres > resp. muscles > muscles relax > decreased lung volume
thirst reflex
decreased water levels/increased osmotic pressure > osmoreceptors in the hypothalamus > osmoregulatory centre in hypothalamus > brain develops conscious desire for water >> thirst >> consume water/drink > increases water levels/lowers osmotic pressure
