Topic 7 Flashcards
Water balance
Regulation of water levels in blood and body fluids, cells and molecules can function properly.
Urination
The removal of excess water, ions and urea from the body via the kidneys
Urine
Mixture of water, urea and excess minerals that is filtered from the blood by the kidneys and excreted
Filtration
The separation of specific substances such as urea, water and minerals which are filtered from the blood by the kidneys
Selective reabsorption
The kidneys reabsorb key molecules such as glucose and some ions and water depending on how concentrated the blood is
How kidneys contribute to balancing water levels
Kidneys control the concentration of urine that is excreted and can change the levels of water that is filtered, so that water levels are maintained
Nephron
Microscopic tubules of the kidney that act as functional units, nephrons are the site of filtration in kidneys
Collecting duct
The portion of the nephron where water reabsorption is regulated via anti-diuretic hormone, several nephrons empty into each collecting duct and this is the final region through which urine must pass on its way to the ureter
Negative feedback cycle
Where a change in something brings about a process that causes the opposite effect, keeping levels constant
ADH
Anti-diuretic hormone which causes more water to be reabsorbed back into the blood from the kidneys if blood water levels are low\
Kidney tubules
Where ADH acts to increase the permeability so that more water is reabsorbed back into the blood
Permeability
The ability of particles to move through a membrane
Pituitary gland
The master gland where ADH is released
Concentrated blood negative feedback
If water levels in the blood become too low, ADH is released to counteract the change
Dilute blood negative feedback
If water levels in the blood become too high, ADH is inhibited to counteract the change
Difficulties regarding water balance
There is no control over water, ion or urea loss by the lungs or skin
Kidney transplant
The transfer of a healthy kidney by a donor to a person with kidney failure, depends on donor lists and there is risk of rejection
Dialysis
A procedure to remove waste products and excess fluid from the blood in individuals with kidney failure
Counter-current system in dialysis
Ensures that a diffusion gradient for urea is always maintained, otherwise urea could be reabsorbed
Hemodialysis
Uses a machine and filter to remove waste products and excess water from the blood
Peritoneal dialysis
Uses a catheter and a fluid that is placed in the abdominal cavity to remove waste products and excess water from the blood
Issues of transplants and dialysis
Transplants can be rejected by the body unless treated with medication and dialysis affects lifestyle or can lead to diseases if complications occur
Dialysis fluid concentrations
Dialysis fluid must contain similar concentrations to blood plasma to prevent cells bursting/shrinking and to maintain a concentration gradient