Notes on Endocrine System | Psychology

The endocrine system performs the function of maintaining the chemical balance in an organism. The endocrine glands which are located in the different parts of the human organism secrete chemical substances known as ‘hormones’. Hormones are secreted directly into the blood stream by the ductless glands.

There are two kinds of glands, viz., duct or exocrine glands and ductless glands or endocrines. The former are glands of external secre­tion, while the latter are glands of internal secretion. The former discharge their products through ducts or little tubes into a body cavity or on the surface of the body. They separate chemical substances from the body fluids and form new chemical compounds.

This process is called secretion. Salivary glands, liver, pancreas, other digestive glands, tear glands, and sweat glands are important duct glands. Saliva is secreted by the salivary glands in response to the taste or smell of food. The liver gland secretes bile; the pancreas gland secretes the pancreatic juice.

The other digestive glands secrete other digestive juices. They respond to the presence of food. The sweat glands secrete sweat in response to heat and to the excitation of the autonomic nervous system. The tear gland secretes tears.

Ductless glands of endocrines discharge their products directly into the blood stream through the walls of the blood vessels which interpenetrate the glands. Their secretions are called hormones. The adrenal glands, the thyroid glands, the pituitary gland, and the sex glands or gonads are ductless. They are intimately connected with emotions.

There are two adrenal glands, one lying close to each kidney. Each adrenal gland consists of two parts, a central gland core or medulla and a cortex surrounding it. The medulla produces the hormone called adrenalin. The cortex produces the hormone called cortin.

The adrenalin hastens and strengthens the heart-beat, increa­ses the blood pressure, stimulates the circulation, removes the fatigue of muscles, arrests the digestive activities of the stomach, expands the pupil of the eye, and produces perspiration.

Excessive secretion of adrenalin produces excessive muscular activity, emotivity, and restlessness. Deficient secretion of adrenalin produces fatigability of muscles and weak responsiveness. Cortin acts as a general stimulant. Its deficiency produces weakness and languor, aversion to activity, and loss of sex interest. Its over activity pro­duces increased masculinity in both sexes.

The thyroid gland lies at the base of the neck in the front of the windpipe. It secretes the hormone called thyroxin, the main consti­tuent of which is iodine. It speeds up metabolism and stimulates the growth of the body and the development of the mind. If the gland is defective, growth is stunted, and intelligence is impaired. Overactive thyroid brings on sluggishness.

Near the thyroid glands there are parathyroid glands which have something to do with the removal of toxic products from the body. The parathyroid hormone is a quieter, while the thyroid hormone is a stimulator. The absence of the parathyroid hormone makes the nervous system over excitable.

The presence of this hormone restores the nervous system to relative calm. Excessive parathyroid hormone produces lassitude and lack of interest. Deficient para­thyroid hormone produces muscular tenseness, and quick and intense response to stimuli.

The pituitary gland is attached to the under-side of the brain. It is called “the master gland” because its hormones affect most of the other glands. It has an anterior lobe and a posterior lobe. The former produces hormones that stimulate the thyroid, the adrenal, and the sex glands.

The latter produces hormones which regulate blood pressure. The former has great influence on the growth of bones. Its over-activity produces a giant, and its under-activity produces a dwarf.

The sex glands or gonads are vitally connected with sex emotions. The male sex hormones produce development in the direction of masculinity. The female sex hormones produce development in the direction of feminity. The lack of gonadal hormones tends to make a person of either sex neutral or devoid of sex characteristics.

The hormones produced by the endocrine glands are carried by the blood stream throughout the whole body. The functions of the different ductless glands are interrelated to one another. A disorder in the function of one gland may cause disorders in the functions of others.

The functions of the endocrine glands have not yet been determined precisely. The science of endocrinology is still in an infant state. Thus personality is to a great extent, influenced by the hormones secreted by the ductless glands or hormones.