L3 - homeostasis Flashcards
define homeostasis
the dynamic maintenance of physiological variables within a certain range
why do we need homeostasis
short term - survival
long term - maintenance of health&wellbeing
what factors have to be maintained for immediate survival
o2 and glucose supply to all cells
extra&intracellular fluid osmolarity and volume
blood co2 content and pH
how are o2 and glucose supplies maintained
- glucose metabolism
- regulated blood pressure&flow
- regulated lung ventilation
what factors have to be maintained for med/long term survival
- optimal functioning of organs
2. fulfilling dietary requirements
describe hierarchy of importance
a factor of immediate importance may be maintained at expense of other variables important in long term
example of hierarchy of importance
too much salt - drink water - increases blood vol - increases MABP - hypertension
describe negative feedback
a response that acts to reverse a change in a variable (normalisation)
describe feed forward mechanism
anticipation of change in a variable brings about a response before the change is detected
eg fight or flight or anticipation of a meal
describe positive feedback
changes in variable trigger response that causes further change in that variable
function of integrating centre in eliciting a response
compares incoming info to ‘set point’ and elicits response if needed
where are neuronal integrating centres found
midbrain & brainstem (hypothalamus/pons/medulla)
what does the brain stem consist of
hypothalamus
pons
medulla
what homeostatic factors are regulated by brain
temp
osmolarity
blood pressure&flow
ventilation
example of peptide hormones
ADH
oxytocin
GH
