Biological Bases of Behavior Part Four – The Endocrine System

The Endocrine System Neurons and neural communication aren’t the only way information is communicated by our bodies. Sometimes, an alternate system communication called the endocrine system, is used. The endocrine system operates by use of specialized groups of cells called glands, which secrete chemicals, called hormones. Biological Basis 4

The Endocrine System While the neural communication is fast, to allow us to react quickly to environmental stimuli, the endocrine system is slower and represents more long-term information transfer. Biological Basis 4

Hormones and Glands Hormones foster growth and proliferation of cells, as well as growth and development of the body in general. Hormones perform their work by interacting with receptors on the surface of target cells, or by entering the cells and interacting with specialized molecules inside them. Biological Basis 4

Hormones and Glands Hormones are similar to neurotransmitters in that they are chemicals which interact with receptors on one cell after being secreted by another, and like neurotransmitters, hormones are key aspects of internal communication; some acting as neurotransmitters when secreted by neurons. Hormonal control is largely an unconscious process, by which the body monitors the levels of the given hormone and the activities it affects through a negative feedback loop. Biological Basis 4

The Adrenal System The adrenal glands are located above the kidneys in two parts. The first is the adrenal medulla and the second is the adrenal cortex. The adrenal glands are important for our energy levels, moods, and stress reactions. Biological Basis 4

The Adrenal System The medulla secretes two hormones: epinephrine and norepinephrine. These two chemicals are also neurotransmitters in the nervous system, and they are important for arousal and the fight-or-flight response of the autonomic nervous system. Biological Basis 4

The Adrenal System The adrenal cortex produces more than 50 hormones for various functions vital for a physiological survival and reproductive function. Anabolic steroids, synthetic forms of male sex hormones produced by the adrenal cortex can cause hyperaggression, mood swings, and mental instability if taken in high doses. Biological Basis 4

3 The Endocrine System Endocrine Glands Pituitary Gland Thyroid Gland Adrenal Glands Pancreas Ovaries/Testes Biological Basis 4

The Thyroid and Pituitary Glands The thyroid gland regulates the metabolic rate of cells by producing the hormone thyroxine. Biological Basis 4

The Thyroid and Pituitary Glands Overproduction of this hormone can lead to hyperthyroidism, which is characterized by weight loss, high blood pressure, and muscular weakness. Too little causes hypothyroidism, associated with slow metabolism, weight gain, and sluggishness Biological Basis 4

3 The Endocrine System Endocrine Glands Pituitary Gland Thyroid Gland Adrenal Glands Pancreas Ovaries/Testes Biological Basis 4

The Thyroid and Pituitary Glands The pituitary gland is sometimes called the master gland because many endocrine glands release hormones in response to hormones released by the pituitary. Biological Basis 4

The Thyroid and Pituitary Glands The pituitary, is in turn, controlled by the hypothalamus (in the forebrain) to which it is attached. Biological Basis 4

The Thyroid and Pituitary Glands The pituitary acts as a bridge between the endocrine system and the nervous system; the nervous system signals a stressful situation to the brain, and the brain stimulates the pituitary to release adrenocorticotropic hormone (ACTH), our primary stress hormone, to affect other organs, such as the adrenal glands. Biological Basis 4

3 The Endocrine System Endocrine Glands Pituitary Gland Thyroid Gland Adrenal Glands Pancreas Ovaries/Testes Biological Basis 4

3 The Endocrine System Endocrine Glands Pituitary Gland Thyroid Gland Adrenal Glands Pancreas Ovaries/Testes Biological Basis 4

3 The Endocrine System Endocrine Glands Pituitary Gland Thyroid Gland Adrenal Glands Pancreas Ovaries/Testes Biological Basis 4