14- homeostasis Flashcards
homeostasis
maintenance of a stable internal environment within restricted limits in organisms
Negative feedback
coordination between receptors and effectors to control conditions around set optimum points
Positive feedback
amplifies changes rather than reversing them (blood clotting, childbirth)
nervous system
info transmitted as electrical impulses travelling across NEURONES
endocrine system
info transmitted as chemical messengers(hormones) in BLOOD
long distance
steps to produce urea in the liver from a.a
deamination: remove amine group+H atom -> ammonia
urea cycle: combine with CO2 -> keto acid remains
remaining keto acid is
enters krebs cycle to be respired
converted to glucose
converted to glycogen/fat for STORAGE
Bowman’s capsule (renal capsule)
surrounds glomerulus(filtration) + contains cells called podocytes in its inner layer
PCT
reabsorbs useful substances(water, glucose, and salts) into surrounding capillaries
- epithelial cells in its wall have microvilli to increase SA
Loop of Henle
extends from the cortex into the medulla and then back into cortex, creates high SOLUTE gradient in medulla, helps reabsorption process
DCT
reabsorbing water into surrounding capillaries, influenced by ADH. surrounded by fewer capillaries than PCT
ultrafiltration action
- high hydrostatic pressure in glomerulus
- causes water, glucose, salts, urea to pass out capillary
- through pores in capillary endothelium
- through basement membrane
- proteins, platelets too large remain in blood
adaptations of epithelial cells in PCT
- microvilli
- basal infoldings- further increase the surface area for moving substances into surrounding blood capillaries
- numerous mitochondria
- co-transporter proteins in plasma membrane- co-transport of substances from filtrate into epithelial cells
order of membrane in reabsorption
PCT lumen
epithelial cells lining PCT
capillary
ADH features
where: produced, stored
- produced in hypothalamus
- stored in pituitary gland
target cells: those lining PCT and collecting duct in kidneys
ADH action
- attaches to receptors on CSM of cells in DCT and collecting duct
- triggers activation of cAMP, initiating a series of reactions that lead to the phosphorylation of aquaporins
- aquaporin vesicle merges with cell membrane
- water moves through aquaporins by osmosis from DCT+collecting duct into surrounding interstitial space
- water reabsorbed into surrounding vessels
suggest reasons why the water potential of blood may decrease
- sweating
- ingestion of salty food
- dehydration
- high solute conc in blood
disease where ADH isn’t produced
what happens when ADH can’t bind to receptor proteins
- fewer aquaporins added to membrane
low permeability to H2O
