Unit 4.6

Introduction The endocrine system uses chemical messages called hormones to transfer information around the body Hormones are responsible for controlling many processes in your body, such as the storage and release of glucose into the blood.

Glands of the Endocrine System Pituitary gland Thyroid gland Pancreas Adrenal gland Ovaries Testes Each having a set role to play in the regulation of bodily functions

Hormones Are chemicals produced by endocrine glands which are located in many various parts of the body. The endocrine glands work together as a system, yet they are not centrally controlled like the nervous system is. Hormones regulate functions like growth, development, water balance, sexual reproduction and the rate of chemical reactions in the bodies cells.

How hormones work Produced and released by the gland into the body Travel throughout the body. Certain cells respond to the hormone [chemical], all others ‘block it’. When reaching the target cell they trigger a certain activity or ‘task’ for the cell. The kidneys clean the hormones out of the blood so they do not build up in the body.

Why hormones? The endocrine system works more slowly than ‘instant’ reactions of the nervous system. A hormone triggered cells will usually react for a longer period of time Hormones are ideal for controlling long-term activities such as reproduction, growth and development.

Systems working together Both the nervous system and the endocrine system respond to a stimulus. Sometimes they work together, as in the case of fear. The nervous system responds quickly, the shock/surprise reaction and the endocrine system prepares the body for a long term response of fight or flight by releasing adrenalin into to blood stream.

Systems working together The pituitary gland, located at the base of the brain is considered the ‘master’ gland. It has influence on the function of many of the body's other glands. The Pituitary gland receives messages directly from the brain, providing a connection between the nervous and endocrine systems.

Examples of chemical control Controlling growth Controlling glucose levels Diabetes Pheromones

Growth Growth is controlled by the hypothalamus, pituitary and thyroid glands. A number of hormones are required for growth, imbalances in these can cause developmental problems of both a physical and mental nature. Some hormones are, TSH, thyroxin and HGH.

Diabetes A disease in which the blood glucose levels are not maintained in the required range for healthy living. Type I and type II.

Pheromones These are chemicals released into the environment by an animal to affect the behaviours and or development of others around it. To attract a mate To mark territory To mark food trails

Activity Consider the messages relayed by the endocrine system compared with messages relayed by the nervous system. List 5 or more examples of each. Suggest reasons why the body would have two different messaging systems.

Homework page 147 Q