Homeostasis

• Homeostasis involves physiological control systems that maintain the internal environment within restricted limits
• Negative feedback - a series of changes resulting in a return to the original level.
• Positive Feedback - a process which results in a departure from the original level becoming further away from its original level.
• The possession of separate mechanisms involving negative feedback controls departures in different directions from the original state, giving a greater degree of control.
• If blood glucose concentration becomes too high, this will lower the water potential of the blood; water will then move out of cells, by osmosis. Causing them to shrivel and die.
• If blood glucose is too low, there will be insufficient respiration occurring so the cells will lack ATP and be unable to complete their normal metabolic processes.
• Glucose - a monosaccharide, the main respiratory substrate
• Glycogen - a polysaccharide, made up of alpha glucose joined by glycosidic bonds
• Glucagon and insulin - hormones used to regulate blood glucose concentration
• Glycogenesis - conversion of glucose molecules into glycogen
• Gluconeogenesis - conversion of amino acids and glycerol into glucose
• Glycogenolysis - the hydrolysis of glycogen into glucose
• Blood glucose concentration is regulated by the Islets of Langerhans which is a tissue in the pancreas
• Alpha Cells - have receptors which detect a decrease in blood glucose concentration and secrete the hormone glucagon
• Beta Cells - have receptors which detect the increase in blood glucose concentration and secrete the hormone insulin