Multicellular Organisms 3 b Hormones are chemical messengers

Multicellular Organisms 3 b

• Hormones are chemical messengers and are released from endocrine glands. These hormones are carried around the body in the bloodstream. • The tissues that hormones act on are known as target tissues. Target tissues have cells with receptor proteins for hormones. This makes hormones specific to their target tissue.

Pituitary • Hormone: – Anti diuretic • Target organs: – Kidneys • Effect: – Controls water balance

Thyroid • Hormone: – Thyroxine • Target organs: – All cells • Effect: – Controls metabolic rate

Adrenal • Hormone: – Adrenaline • Target organs: – Liver / Heart • Effect: – Prepares body for action

Pancreas • Hormone: – Insulin • Target organs: – Liver • Effect: – Controls blood sugar levels

Ovary • Hormone: – Oestrogen • Target organs: – Uterus /ovaries / pituitary gland • Effect: – Controls puberty and menstrual cycle in females

Testicles • Hormone: – Testosterone • Target organs: – Male reproductive organs • Effect: – Controls puberty in males

• Carbohydrates obtained in the diet are broken down into glucose. Blood glucose level must be kept within a certain concentration range in the body so that there is a steady supply of energy for the cells. • The pancreas monitors and controls the concentration of glucose in the blood.

• When blood glucose levels increase, a hormone called insulin is released by the pancreas. This converts excess glucose into glycogen which is then stored in the liver.

• When the blood glucose levels decrease, a hormone called glucagon is released by the pancreas. This converts stored glycogen in the liver back into glucose which is then released into the blood stream. Glucagon is needed when glucose is gone

• Diabetes is a disease where the concentration of glucose in the blood is not controlled properly by the body. There are two types of Diabetes.

• Type 1 diabetes develops when the insulin-producing cells in the body have been destroyed and the body is unable to produce any insulin.

• Type 2 diabetes develops when the body can still make some insulin, but not enough, or when the insulin that is produced does not work properly

• Both types can lead to high levels of glucose in the blood, which can be fatal. There are two types of treatment for diabetes: 1. Careful monitoring of food intake, with particular care taken over carbohydrates which are digested into glucose.

2. Injecting insulin into the blood before meals. The extra insulin causes glucose to be taken up by the liver and other tissues. Cells get the glucose they need for respiration, and the blood glucose concentration stays normal.