2.1 Insulin

Secrete hormones – insulin and glucagon that work together to regulate the blood glucose level, directly into the bloodstream. (Normal blood glucose level: 70-150 mg/dL).
Beta cells of Islets of Langerhans release insulin while alpha cells of Islets of Langerhans release glucagon.
Hormones are circulated round the body until they reach the target organs where they exert their effects.

2.1 Effects of insulin

1. Stimulates liver cells to convert excess glucose into glycogen.

2. Stimulates synthesis of lipids.

3. Inhibits lipolysis, proteolysis, glycogenolysis and gluconeogenesis.

2.2 Regulation of blood glucose concentration

When blood glucose concentration is above normal level, the pancreas which is the receptor detects the rise in blood glucose concentration.
Beta cells of Islets of Langerhans release insulin.
Insulin stimulates liver cells to convert excess glucose into glycogen.
When blood glucose concentration returns to normal, there is a negative feedback to the pancreas to reduce the secretion of insulin.

2.3 Diabetes mellitus

2.3.1 Symptoms of diabetes mellitus

(a) High blood glucose level

(b) Presence of glucose in the urine after a meal.

2.3.2 Types of diabetes mellitus and their respective treatments

1. Type 1 diabetes - Juvenile-onset diabetes

-Islets of Langerhans unable to produce sufficient insulin.

Effects of lack of secretion of insulin

- Glucose cannot be stored or utilized by tissue cells, so blood glucose concentration rises. Some glucose is lost in the urine.
- Weight loss
- Body oxidises fats instead of glucose to release energy. This results in the production of poisonous substances known as ketones that are excreted in the urine.

Treatment: Inject appropriate amount of insulin at fixed time intervals.

2. Type 2 diabetes - Late-onset diabetes

-Cells do not respond well to insulin.

-Treatment: Reduce the intake of carbohydrate in the diet and exercise regularly.

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