physiological homeostasis Flashcards
define homeostasis
the regulation of a constant internal environment, disregarding the external environment
define behavioural homeostasis
behaviours that you actively choose to do
give examples of behavioural homestasis
- eating whilst not hungry
- holding breath whilst swimming
- drinking regularly from a bottle
define physiological homeostasis
actions that you do not actively choose to do - they are caused by physiological triggers
give examples of physiological homeostasis
- increased heart rate whilst exercising
- fever when unwell
- increased urination whilst drinking
cellular homeostasis example
control of [Ca2+]i
why is intracellular calcium concentration closely regulated
calcium is a biological stimular which stimulates various different components (smooth, skeletal and cardiac muscles)
what concentration does intracellular calcium maintain at
1x10-7 M
organ/system homeostasis example
- perfusion
- renin-angiotensin system (causes vasoconstriction, increasing BP)
whole organism homeostatic example
thermoregulation
why is thermoregulation important
body temp must be controlled because most of our intracellular functions are temperature dependant
name factors which are under homeostatic control
- nutrients (glucose)
- temperature
- blood volume and pressure
- pH
- gases (pCO2 and pO2)
- waste products (urine)
what do negative feedback loops do
act to reduce an effect
give an example of a negative feedback loop
hypothermia
describe an example of a negative feedback loop
hypothalamus registers decreased body temp - smooth muscles vasoconstrict (become pale - keeping blood away from skin surface), skeletal muscle begins to shiver, pili (hair) erects to induce a heat blanket of air over skin
= body temp increases
what do positive feedback loops do?
act to increase an effect
give an example of a positive feedback loop
blood-clotting cascade
describe an example of a positive feedback loop
thrombin (a hormone) allows blood to clot, which creates a scab on a wound
what is feedforward control
an anticipatory change to a physiological variable
give an examples of feedforward control
salvation in anticipation of eating
why do physiological set points need to be modified
because if the body is working abnormally, the set points need to adjust to account for the abnormalities
give examples of modifying set points
- body temp for pyrexia
- prostoglandin E2 for a fever
