Heredity and Hormones

The endocrine system helps coordinate and integrate complex psychological reactions in our bodies. The endocrine system works together with the nervous system I a constant chemical conversion. The endocrine glands release hormones that are carried by the bloodstream. Hormones carry messages and may take seconds or minutes to reach their goal.

(Psychology, 2005) "At first stages of development, hormones organize the nervous system and body tissues." During puberty hormones trigger development of sex characteristics such as breasts, voice changes, pubic hair, and underarm hair. Hormones also activate behaviors such as being alert or sleepy, excitability, sexual behavior, being able to concentrate, being aggressive, stress reaction, and desire for companionship. They also have dramatic effects on mood, emotional reactions, learning, and resisting diseases. Changes in hormones can cause psychological disorders like depression.

The endocrine glands are the pineal gland, pituitary gland, parathyroid gland, thyroid gland, pancreas, adrenal gland, ovaries, and testes. The thyroid gland is just below the larynx. The hormone it produces is thyroxin which regulates the rate of metabolism. If the thyroid is overactive than it can produce symptoms such as insomnia, over excitability, fatigue, reduced attention span, acting out, agitation, and snap decisions. Not enough thyroxin causes the feeling of being constantly tired.

The pineal gland is very small and is in the middle of the brain. Its hormone is called melatonin which helps regulate the sleep-wake cycles. When disturbed it causes what people call jet lag.

The pancreas is located between the stomach and small intestine. It controls the blood sugar level using the hormones insulin and glucagon. Having low insulin causes diabetes mellitus which is too much sugar in the blood and urine. Too much insulin causes fatigue called hypoglycemia which is when there is not enough sugar in the blood.

The pituitary gland is on the underside of the brain and is connected to the hypothalamus. It has the most hormones and causes the most effects on the body's functions such as blood pressure, contractions, thirst, producing milk, growing, sexual behavior, water in body cells, and other functions. Since it has the biggest role in regulating the endocrine glands, it is called the master gland.

The gonads (testes and ovaries) consist of hormones called masculine, androgens, and feminine, estrogens. Both hormones are found in males and females, but males have more androgens and females have more estrogen.

There are two adrenal glands that are found above the kidneys. An adrenal gland consists of an inner core, adrenal medulla, and an outer layer, adrenal cortex. These effect the reactions to stress. The hormones are epinephrine, which activates the sympathetic nervous system, and norepinephrine, which raises blood pressure and is carried by the