homeostasis Flashcards
what is homeostasis and what does it affect
maintenance of contant stable internal environment despite external changes within restricted limits
controls ph, bgl , temperature
too high bgl- wp reduced cells shrivel and die
too low- no respiration
negative and positive feedback
neg- restores to norm
pos- further increases deviation eg contractions in childbirth
when does bgl rise and fall
rises after eating , falls after excericse
role of pancreas
endocrine tissue that has islets of langerhans. a cells secrete glucagon and b cells secrete insulin
in the liver
1glycogenesis
2glycogenolysis
3gluconeogenesis
1 glucose to glyogen - when bgl too high
2 glycogen to glucose - when bgl low
3 make glucose from non carb sources - when bgl low
if bgl too high
insulin secreted, binds to receptors on liver and muscle cells
changes tertiary structure of glucose channel proteins so more glucose into cell via facilitated d
incr absorption of glucose to cells
insulin activates enzymes to do more gylogenesis
incr rate of respiration
incr conversion of glucose to fat
if bgl too low
glucagon secreted binds to specific protein receptors on liver cells which causes glyogenolysis and gluconeogenesis to happen to incr amount of glucose in blood
also decr rate of resp in cells
what is the role of adrenaline
if bgl too low, secreted by adrenal glands,binds to receptors on liver cells
activates glycogenolysis and activates glucagon secretion
reduces insulin and glycogenesis
2nd messenger model
adrenaline and glucagon bind to transmembrane protein receptors, changes the shape and activates adenylyl cyclase which converts atp to camp.
camp binds to protein kinase a to do glycogenolysis
diabetes type 1 vs type 2
type 1- immune system attacks b cells, bgl stays high, stops synthesis of insulin, treat w insulin injections and eat less carbs
type 2 - cant make enough insulin, bgl high, contol w excercise and good diet
why does wp fluctuate
incr - diet, resp
decr- sweat, urination , breathing
making the glomerular filtrate
diameter of afferent arteriole bigger than efferent so buildup of hydrostatic pressure in glomerulus
water glucose and minerals squeezed out capillary to form gf
blood cells and proteins cant get through into renal capsule as too big since wall of glomerulus is 1 cell thick
what is the movement of gf resisted by
capillary endothelial cells
connective tissue,
low wp of glomerulus
adaptation of glomerulus
renal capsule inner layer has podocytes which let filtrate pass through easier
reabsorption of glucose and water by pct
na + actively transported out cells lining the pct into the blood capilaries so na+ conc in pct low
na+ diffuse down conc grad from lumen of pct into epithelial cells via faciliated diffusion. they take glucose w them (co transport)
now the glucose and na+ and wateer into pct they diffuse into blood and are reabsorbed
adaptations of pct
microvilli -large sa to reabsorb h20 and glucose
lots of mitochondria for active trans of na+
infoldings of basal membrane to incr sa
maintaining na+ grad in medulla by loop of henle
loh produces na+ to allow water to be absorbed by collecting duct
na+ actively transported out ascending limb , impermeable to water, so wp lowered in surrounding medulla
in descending, water moves out via osmosis and na+ moves in.
at lowest point, lowest wp of filtrate
countercurrent system
between the filtrate in the collecting duct and the fluid in the medulla. although diff in wp are low, grad is maintained along whole length of collecting duct
reabsorption of water by dct and collecting duct
cells lining dct have microvilli and mitochondria for active transport
these help h20 and salt levels in filtrate to adjust to help control ph and water level of blood
permeability of dct wall adjusted depends on how much water needs to be absorbed
how does adh deal w low wp
osmoreceptors in hypothalamus detect fall in wp as they shrink via osmosis
so hypothalamus makes adh which goes to pituatry gland and secreted by kideny
receptors on dct and collecting duct bind w adh , which actives phosphorylase
this causes vesicles in cell to fuse w cell surface membrane and plasma membranes w aqua porins let out. membrane becomes more permeable to h20.
also incr permeability of collecting duct to urea which lowers wp of fluid around duct so more water leaves cs via osmosis down grad and enters blood
