Control of Blood Water Potential Flashcards
Define Osmoregulation
- maintaining water potential of the blood within restricted limits
Which body parts are heavily involved in osmoregulation
- hypothalamus
- pituitary gland
- kidneys
what is the functional unit of the kidney and how many are there in each kidney
- the nephron
- approximately 1 million nephrons in each kidney
what are the two parts of the kidney
- the cortex (outer part) and the medulla (inner part)
what does the cortex of each kidney contain
- the glomerulus
- renal capsule
- proximal convoluted tubule
- distal convoluted tubule
what does the medulla of each kidney contain
- part of the loop of Henle
- the collecting duct of each nephron
describe the process of ultrafiltration
- High hydrostatic pressure (due to contraction of left ventricle) in glomerulus forces small molecules (glucose, amino acids, water, ions, urea) into the renal capsule through fenestrations and the basement membrane
- blood cells and large plasma proteins stay in the blood
how much of each substance is reabsorbed out of the glomerular filtrate and how
- most of the water via osmosis
- some small proteins via diffusion
- most of the ions via facilitated diffusion/active transport
- all of the glucose/amino acids via co transport
where in the kidney are substances reabsorbed
- into the cells lining proximal convoluted tubule (PCT)
describe and explain adaptations of the cells lining the PCT
- microvilli = large surface area
- numerous mitochondria = provide ATP for active transport
- continuous movement of blood = maintains concentration gradient for further reabsorption
- close to capillaries = short diffusion pathway
how does the loop of Henle allow for the production of concentrated urine
- Na⁺ and Cl⁻ ions actively transported out of ascending limb = high ion conc in the medulla tissues
- water osmoses out of the descending limb as it has a higher water potential than surrounding medulla tissues
- filtrate then becomes more concentrated as it moves up the ascending limb
what feature of the loop of Henle allows it to function
- the descending limb is permeable to water and the ascending limb is impermeable to water
what are aquaporins
- water protein channels that enable the absorption of water via osmosis
describe the role of ADH (Anti-Diuretic Hormone) in the control of blood water potential
- ADH attaches to specific receptors on the cells of the DCT and collecting duct and stimulates the inclusion of aquaporins to the cell surface membrane of their cells
- this increases the permeability of water allowing more water to osmose out and into the kidneys
what are osmoreceptors
- receptors in the hypothalamus that are sensitive to the water potential of the blood
what happens when there is a decrease in the blood water potential
- osmoreceptors in the hypothalamus are stimulated which stimulates the production and release of ADH to the posterior pituitary gland
- ADH increases the permeability of the distal tubule and collecting duct, so more water is reabsorbed from the filtrate into the blood increasing the blood water potential
- this produces a smaller volume of more concentrated urine
what happens when there is a increase in the blood water potential
- osmoreceptors in the hypothalamus are less stimulated which decreases the production and release of ADH to the posterior pituitary gland
- less ADH means less permeability of the distal tubule and collecting duct, so less water is reabsorbed from the filtrate into the blood decreasing the blood water potential
- this produces a higher volume of less concentrated urine
what mechanism regulates blood water potential
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