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
examples of hormones that are glycoproteins
LH
FSH
TSH
what is meant by local homeostatic responses and give example
independent of endocrine and neuronal
eg local control of blood flow during exercise
