The Endocrine System

The Endocrine System There are normal physical responses to scary situations. The endocrine system controls the conditions in your body by making and sending chemicals from one part of the body to another. Most responses of the endocrine system are controlled by the autonomic nervous system, because they occur automatically (without your control).

Hormones Hormones are chemicals that are made in one organ and travel through the body to a second organ (called a “target organ”). The target organ responds to the chemical. Most hormones have more than one target organ, and many hormones affect all the cells of the body. Because hormones are made at one location and function at another, they are often called chemical messengers. The hormone binds to the receptor in the target organ and chemical changes occur. Different types of hormones have different jobs. Examples include: adrenaline, insulin, and estrogen.

Glands Glands are the structures that produce and release hormones!! Pituitary Gland Director of the endocrine system!! Located at the base of the brain (right above the roof of your mouth). Hormones produced here control growth, sexual development, and absorption of water. Pineal Gland Buried deep in the brain (also about the size of a pea). Sensitive to light, and necessary for sleep, body temp, reproduction, and aging. Thyroid Gland Found in your throat near your Adam’s apple. Necessary for growth and metabolism and regulation of calcium.

Glands Continued Thymus Adrenal Gland Located in your chest. Continues to grow until puberty when it then begins to shrink. Helps the body fight disease by controlling the production of WBC’s called T cells. Adrenal Gland Located on top of your kidneys. Produces 30 different hormones that regulate carbohydrates, proteins, fat metabolism, water, and salt levels. Some hormones help fight allergies and infections. Also produces adrenaline which makes your heart beat faster.

Glands Continued Pancreas Ovaries and Testes Located beneath the stomach, connected to S.I. Secretes two hormones: insulin and glucagon. These regulate the level of glucose in your blood. Ovaries and Testes Secrete hormones that control sexual development. These organs are not considered part of the “endocrine system” but produce important hormones: Kidneys- produce hormones to regulate RBC production. Heart- produces hormones to regulate blood pressure.

Feedback Mechanisms Hormones are powerful chemicals and are capable of producing drastic changes in our bodies, so their levels must be carefully regulated. Homeostasis is achieved through negative feedback. Most feedback in the body is NEGATIVE Negative Feedback turns OFF the response to the hormone. Example: Thyroid gland releasing thyroxine. Some responses are controlled by POSITIVE feedback. The purpose is NOT to achieve homeostasis, but to produce a response that continues to increase. This is only needed in EXTREME CONDITIONS!! Example: clotting blood, fever, immune response, puberty, labor.

Balanced/Imbalanced Hormones When you ride a bike, you are constantly making adjustments to maintain balance and control despite conditions The pancreas produces two hormones One is insulin which decreases the level of sugar in the blood The other is glucagon which increases sugar levels in the blood The balance of these two hormones maintains stable blood sugar between meals Too little or too much or any hormone can cause serious disease When the pancreas produces too little insulin, sugar levels in blood can rise to dangerous levels Very high levels of blood sugar can damage the circulatory system and the kidneys This is called diabetes where synthetic insulin is injected into the body to replace insulin not being made by the pancreas

Hormone Balance The action of one hormone is balanced by the action of another hormone. Example: the pancreas produces two hormones: insulin (decreases glucose levels) and glucagon (increases glucose levels). The balance of these two maintain stable blood sugar between meals. Too little or too much of any hormone can lead to serious disease. Example: Insulin -> Diabetes