The Endocrine System

The Endocrine System (21:00)

After an introductory segment contrasting the human endocrine and nervous systems, this program addresses the complex physiology of the endocrine system. Topics include the endocrine organs and glands; the characteristics of hormones and the process of signal transduction; hormonal regulation of blood glucose and blood calcium levels; the roles of growth hormone, thyroid hormone, testosterone, and estrogen in bodily development; hormones and reproduction; and hormonal involvement in the fight-or-flight response. A viewable/printable instructor’s guide is available online. A Films for the Humanities & Sciences Production. A part of the series The Human Body: How It Works. (21 minutes)

Endocrine System: Introduction (00:52)
The endocrine system is a collection of organs (glands) that secrete chemical messages called hormones directly into the bloodstream. Hormones control responses that do not have to be immediate.

Hormones and How They Work (02:21)
Hormones are classified as steroids--all the sex hormones, cortisol, and a form of Vitamin D--and nonsteroids--proteins such as insulin, and amines such as thyroid hormone. Hormones produce responses in cells.

Endocrine Organs (03:24)
Endocrine organs include the pituitary, pineal gland, thyroid and parathyroid, thymus, pancreas, kidneys, adrenals, ovaries, and testes. The pancreas secretes two hormones that regulate blood glucose levels.

Blood Glucose Levels (02:22)
Glucose molecules are transported via the blood to all the body's cells. Some tissues store glucose as glycogen. Blood glucose level is maintained primarily by insulin. Glucagon stimulates the liver and muscles to convert glycogen to glucose.

Growth and Metabolism (02:43)
Hormones affect growth either directly or indirectly. Growth hormone stimulates protein synthesis in bone and muscle, and stimulates the use of fat as fuel. Thyroid hormone stimulates metabolism in nearly every tissue in the body.

Endocrine System: Reproduction (00:35)
Estrogens produce female characteristics, and testosterone produces male characteristics. Hormones control the production of eggs and sperm, as well as pregnancy, birth, and milk production.

Endocrine System: Stress (01:54)
When humans are exposed to danger, signals are immediately sent to the medulla of the adrenal glands to release epinephrine (adrenaline) and norepinephrine (noradrenaline). The fight-or-flight response is in full function.

Endocrine System: Mineral Balance (05:01)
Certain minerals are critical to the proper functioning of the human body. The endocrine system ensures that the body maintains the required levels of minerals such as calcium. Water and electrolyte balance must be maintained.