Homeostasis- Kidney Flashcards
Define osmoregulation
Control of water potential of the blood
Role of hypothalamus in osmoregulation
Water potential too low
More water is reabsorbed by osmosis into the blood from the tubules of the nephrons.
More ADH released
Urine more concentrated
Water potential too high
Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons
Less ADH released
Urine more dilute
Where is loop of Henle
Medulla of kidneys
What is kidney medulla made up of
Descending and ascending limb
Role of descending and ascending limbs
Control movement of sodium ions for water absorption
Where is water reabsorbed into the blood
Along most of nephron
Mainly in loop of Henle, distal convoluted tubule, collecting duct
Afferent arteriole
Takes blood into glomerulus
Larger diameter
Blood under less pressure
Efferent arteriole
Takes filtered blood away from glomerulus
Smaller diameter
Blood under higher pressure
Forces small molecules out of capillary endothelium and into Bowman’s Capsule epithelium
Formation of glomerular filtrate
High pressure in efferent arteriole forces liquid and small molecules in the blood out of the capillary and into Bowman’s Capsule- glomerular filtrate
Pass through 3 layers to do so.
Large molecules e.g. proteins stay in blood
Glomerular filtrate passes along rest of nephron + useful substances absorbed along way
3 layers molecules pass through to get from capillary to Bowman’s Capsule
Pass through capillary endothelium, a membrane, epithelium of Bowman’s Capsule
Nephron
Long tubules with bundles of capillaries where blood is filtered
Selective reabsorption
Useful substances leave tubules of nephrons and enter capillary network around them
Useful solutes reabsorbed along proximal convoluted tubule by active transport and facilitated diffusion.
Water enters by osmosis because water potential of blood is lower than filtrate.
Water reabsorbed by PCT, loop of Henle, DCT and collecting duct
Filtrate that remains is urine
Proximal convoluted tubule adaptations
Microvilli for large surface area
Increase diffusion rate
How is the gradient of sodium ions in the medulla maintained by loop of Henle
Top of ascending limb- Na^+ ions actively transported into medulla (impermeable to water)
Lowers water potential in medulla
Water moves from descending limb into medulla by osmosis
Glomerular filtrate more concentrated (descending limb not permeable to ions)
Water in medulla reabsorbed into blood
Bottom of ascending limb- Na^+ ions diffuse into medulla, lower water potential in medulla
Water moves out of DCT by osmosis + reabsorbed into blood
High ion conc + low water potential in medulla
Water moves out of collecting duct by osmosis
Water reabsorbed into blood
How is volume of water reabsorbed in capillaries controlled
Changing permeability of distilled convoluted tubule and collecting duct
How is ADH released into blood
Osmoreceptors in hypothalamus
Detect decrease in water potential of blood
Water moves out of osmoreceptor by osmosis
Cells decrease in volume
Sends signals to other cells in hypothalamus which sends signals to posterior pituitary gland
Sends signal to release hormone ADH
Role of ADH in osmoregulation
ADH molecules bind to receptors on plasma membranes of cells in DCT + collecting duct
Protein channels - aquaporins inserted into plasma membrane.
Walls more permeable to water- increased osmosis rate
More water reabsorbed from tubules to medulla and into blood
Small amount of concentrated urine produced
