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| ===Insulin=== | | ===Insulin=== |
| + | [[Image:Pancreatic Beta Cell.jpg|thumb|right|150px|Pancreatic Beta Cell - Copywright RVC 2008]] |
| + | *Insulin is stimulated under conditions of hyperglycaemia and inhibited under conditions of hypoglycaemia. |
| + | *It has an ''anabolic'' effect on energy sources. |
| + | *It is a small polypeptide consisting of two chains; A and B; which are linked by disulphide bonds. |
| + | **It is synthesised inactively as a pre-pro-hormone which undergoes cleavage to produce the active form. |
| + | *Insulin is released when blood glucose levels are high. The process of insulin release occurs as follows: |
| + | **GLUT 2, which only operate at high glucose concentrations, are present in the plasma membranes of β cells. |
| + | **After a meal, glucose concentrations in the blood rise and glucose is taken into the cell. |
| + | **Glucose is metabolised inside β cell which produces ATP. |
| + | **ATP inhibits potassium channels which depolarises the plasma membrane. |
| + | **Depolarisation causes calcium signalling, which stimulates insulin to be released. |
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| ==Vasculature== | | ==Vasculature== |