Homeostasis and excretion GapFill

While some animals cannot control their internal body temperature and hence rely on behavioural adaptations such as burrowing, mammals are  saprobiontsmutantsectothermsendotherms, so they have a number of physiological adaptations to maintain a core temperature. They often use  paralleltriangularnegativepositive feedback systems to correct a change away from an optimal internal condition using information detected by  effectorsreceptorssynapsesstimuli. For example,  increased respirationosmosisvasodilationshivering may be used as a method of heat loss when internal temperature starts to increase too much.

Water potential must also be carefully controlled by  thermoregulationmyogenic stimulationosmoregulationactinomyosin bridge formation to prevent cells from shrinking or bursting. The  medullahypothalamussinoatrial nodenephron is the functional unit of the kidney, which controls the selective reabsorption of water and minerals in this case. If the water potential of the blood starts to fall too much, the posterior pituitary can produce more of the hormone  glucagonadrenalineADHFSH, which increases the volume of water which is retained in the blood. It does this by increasing the number of  carrier proteinsaquaporinscollecting channelshaemochannels which form in the cell-surface membrane of the distal convoluted tubule and the collecting duct, so more water is reabsorbed.

The rate at which fluid passes through the kidneys, or  glomerular filtration ratenephron diffusion raterenal titration ratediuresis rate, can be used to diagnose potential kidney damage. If this figure is very low it suggests kidney failure, which requires urgent treatment, e.g. by  neurostimulationosmoregulationperitoneal dialysishaemodialysis, during which molecules pass across a partially permeable membrane in the abdomen to restore them to their correct concentrations.

This ultrafiltration and selective reabsorption produces urine which must be removed from the body along with other metabolic wastes, a range of processes known as  excretionosmosisurinationdialysis. The  appendixpancreasliversmall intestine has an important role in this process via detoxification and deamination, as well as being responsible for storing a lot of the body's  glucagonglycogenfatbile. Deoxygenated blood rich in nutrients enters through the  renal veinrenal arteryhepatic portal veinhepatic artery, and amino acids are then deaminated to produce ammonia. However, this is very toxic and so ammonia must enter the  peritoneal cycleornithine cycleKrebs cycleglomerular reaction to be converted to urea, which is less harmful to have in the blood.