homeostasis

homeostasis is the maintenance of a constant internal environment via physiological control systems

• temperature • blood ph • blood glucose concentration

if it is too low then there is not enough kinetic energy for enzyme-substrate complexes to be formed this means the rate of important biological reactions/ processes is too slow

is it is too high then enzymes will denature the body will react to the deviation from normal and return the body back to normal temperature

if ph deviates from optimum, it causes enzymes to denature

if it is too low then it leads to cell death as glucose is required for respiration (both aerobic and anaerobic)

it leads to the blood water potential to decrease, s water leaves cells by osmosis this increases the water potential of cells so water can move back into the cells causing it to burst

negative feedback restores systems back to their normal level when there is a change vai the nervous system

stimulus →receptor →CNS→effector→response the receptor detects the change it then sends the impulse along a sensory neuron to the CNS which contains a relay neurone the impulse is then sent along a motor neurone to an effector that elicits a response

positive feedback: when deviation from the optimum stimulus changes which results in an even bigger deviation from the optimum e.g. contractions during labour contractions releases oxytocin which stimulates even more contractions

positive feedback is not involved in homeostasis because it does not keep your internal environment stable. Positive feedback is useful to rapidly activate processes in the body

positive feedback can also happen when a homeostatic system breaks down for example, hypothermia is low body temperature. It happens when the body has lost heat quicker than it can produce it. As the body temp falls the brain does not work properly and shivering stops. This makes body temp to fall even more Positive feedback takes body temp further away from the normal and continues to decrease unless action is taken

diet exercise levels insulin adrenaline glucogon

excess glucose converted to glycogen by the liver only occurs when blood glucose levels are too high

breakdown of glycogen back to glucose in the liver when glucose levels are too low

creates glucose from non- carbohydrates stores in the live e.g. amino acids and glycerol it occurs when glucose levels are still too low despite glycogenolysis occurring

insulin is secreted when beta cells in the Islets of Langerhans (which are in the pancreas) detect blood glucose levels that are too high

• Insulin attaches to receptors on target cells and changes the tertiary structure of the channel proteins so more glucose is absorbed into the cells by facilitated diffusion • more protein carriers are incorporated into the membranes so even more glucose is absorbed from the blood into the cells • glycogenesis occurs - which is catalysed by activating enzymes once it is absorbed in the cells

• glucagon attaches to receptors on the surface of target cells • this stimulates adenylate cyclase to convert ATP into cyclic AMP (cAMP) • cAMP acts as a second messenger model which contains 1 phosphate unlike three like ATP • cyclic AMP activates an enzyme called protein kinase which hydrolysis glycogen to glucose→ so glycogen action stimulates glycogenolysis • It can also activate enzymes involved in glyconeogensis

molecules inside a cell that transmit signals intracellularly from the binding of an extracellular molecule to a receptor

• adrenaline attached to a receptor on the surface of a target cell • this causes a G protein to be activated and to convert ATP to cAMP • cAMP activated an enzyme that hydrolyses glycogen to glucose this whole process is the flight or flight mechanism

this occurs when the body is unable to produce insulin this starts at childhood most often, the results of an autoimmune disease where beta cells are attacked by antibodies TREATMENT: insulin injections

Receptors on target cells lose responsiveness to insulin and so it leads to a decrease in insulin sensitivity This usually develops in adulthood due to obesity and poor diet → if you have too much glucose/ sugar in your blood due to diet, insulin works soo hard to decrease it your body becomes resistant to insulin TREATMENT: regulating the uptake of carbohydrates, increasing exercise and sometimes insulin injections

It is called osmoregulation