controlling bgc Flashcards
what is the role of the PCT
reabsorbing glucose and water
role of the loop of Henle
Maintenance of a gradient of sodium ions
formation of glomerular filtrate
high hydrostatic pressure in glomerulus
as diameter of afferent arteriole is wider than efferent arteriole
small substances like glucose water and urea are forced out into glomerular filtrate and this filtration takes place by
capillary basement membrane, podocytes and pores between capillary endothelial cells
large protiens remain in blood
reabsorption of glucose by pct
na at out epithelial cells to capillary
na moves by FD into epithelial cells down a conc gradient
bringing glucose against its conc gradient
glucose moves into the capillary via fd down its conc gradient
reabsorption of water by pct
glucose lowers the wp of capillaries
so water moves into the capillaries by osmosis down a wpg
features of cells in PCT allow reabsorption of glucose into blood
microvilli provide LSA
many channel carrier protiens for FD co transport
many carriers for AT
many mitochondria produce ATP for AT
many ribosomes produce carrier and channel protiens
why is glucose found in urine pf untreated diabetic
bcc too high not all glucose reabsorbed at PCT
as the glucose carrier and cotransporter protiens are working at maximum rate
why is it important to maintain a gradient of sodium ions in the medulla
so wp decreases down the medulla
so wp gradient maintained between CD and medulla
maximising reabsorption of water by osmosis of filtrate
ascending limb
NA AT out
filtrate conc decreases
water remains as impermeable to water
increasing conc of na in medulla and lowering the WP
DESCENDING LIMB
water moves out by osmosis then reabsorbed by capillaries so filtrate conc increases
na recycled and diffuses back in
why do animals who need to conserve water need a longer loop of henle
more na moves out so na gradient needs to be maintained for longer in medulla
so wpg maintained for longer
so more water reabsorbed from CD by osmosis
reabsorption of water by cd and dct
water moves out dct and cd by osmosis
down a wpg
controlled by adh which increases their permeability
hypothalamus
contains osmoreceptors
detect increase or decrease in blood wp
produce more adh when wp low
ppg role in osmoregulation
secrete more or less adh in blood due to signals from hypothalamus
adh
attach to receptors on cd and dct
stimulating addition of aquaporins into CSM
so increases permeability of cells of cd and dct to water
so increases water reabsorption from cd and dct back into blood by osmosis
so decreases volume and increases conc of urine produced
