Endocrine System: The glands in the human body are of two types: Human body has two type of glands, Exocrine glands and Endocrine glands.
The exocrine glands produce fluid secretions that are delivered by tubes or duct either to the body surface e.g. glands of skin or to the inner regions where these are required e.g. pancreas delivers its pancreatic juice to the intestine for digesting food etc.
Endocrine glands produce secretions called hormones that are not carried by ducts but are passed into the bloodstream and carried to the target area by blood circulation. The following endocrine glands are present in the human body (Fig 15.9).
Fig 15.9 Endocrine system
- Pituitary gland
- Thyroid
- Parathyroid glands
- Pancreas (Islets of langerhans)
- Adrenal glands
- Gonads
Parathyroid glands
The function of endocrine glands is very much inter-related. Several of the hormones produced by them serve only to alter the functions of other endocrine glands. They serve as double check automatic control over one another.
Pituitary gland
The pituitary gland is known as the master gland in the body and plays an important role in several ways. It has certain hormones which have direct action on the body e.g. the growth hormone.
In addition it has hormones which control the action of the other endocrine glands. It is closely associated with the base of brain in the skull. In size it is a little larger than a garden pea. There are two lobes of pituitary gland each produces its own hormones.
- Anterior Lobe
- Posterior Lobe
Anterior lobe produces many hormones. One of the important hormones produced by the pituitary is somatotrophic (STH) which is the growth promoting hormone due to which the process of growth takes place in the body. Influences all those organs and tissues of the body concerned in the process of growth.
Another important hormone is thyroid stimulating hormone (TSH) which stimulates the thyroid to produce its hormone. The remaining hormone of the anterior lobe of pituitary influences the activities of reproductive organs both in men and women but in different ways and controls the working of adrenal glands.
1. Endocrine System – Two hormones are produced by the posterior lobe of pituitary gland. One hormone helps to conserve water in the body according to requirement, and the other has no effect on males but has certain effect in females.
2. Thyroid gland
The thyroid gland is located in the neck and fits closely around the from and side of trachea (wind pipe) just below the organ of voice of larynx. The thyroid receives a lot of blood supply to nourish its cells and to carry away the hormones it produces. It produces two hormones.
1. Thyroxin 2. Calcitonin
The above hormones of thyroid are produced under the influence of TSH from the pituitary gland. The thyroid hormones increase the consumption of oxygen by the body tissues. This increases the rate of metabolism. They also increase the ability of a person the think. Adequate supply of these hormones is also needed for normal growth and skeletal development in children.
Goiter (abnormal enlargement of thyroid) is due to its malfunction. The major cause of this disease is iodine deficiency is iodine deficiency in the food / body.
3. Parathyroid gland
These are very small structures usually four in number embedded in the back side of the thyroid gland. They produce parathyroid hormones which control the amount of calcium and phosphate in the blood serum.
4. Pancreas
Pancreas is present in the abdominal cavity close to the stomach. Pancreas is known as double gland as it has two kinds of glandular tissues. One exocrine and the other endocrine in function. The main bulk of pancreas is exocrine that produces pancreatic juice which helps in the digestion and is carried by the pancreatic duct to the intestine. Distributed at various places in its tissue are groups of cells, known as islets of Langerhans which are endocrine (not having ducts). The islets of Langerhans produce two hormones:
1. Insulin 2. Glucagon
These two hormones have opposite effect in regulating use of glucose in the body. The two hormones therefore counter balance each other. When the amount of glucose in the blood plasma increases the production of insulin is also increased due to which the entry of glucose into muscles and other tissue from blood is made easier. In the absence of insulin the glucose level in the blood is raised resulting in the disease known as diabetes mellitus. (Diabetes =to go through; mellitus = honey)
Another form of diabetes is diabetes insipidness in which there is excessive flow of urine.
Too much insulin in the blood may cause lowering of glucose level to such an extent that it may result in unconsciousness and death. Glucagon, the second hormone in such emergency situations brings about release of stored blood sugar so as to maintain a proper level of glucose in the blood.
5. Adrenal glands
Adrenal glands are paired and lie in abdominal cavity above the kidneys. Adrenal glands produce adrenaline which prepares the body for action in an emergency by raising blood pressure, increasing heart and breathing rate.
6. Gonads
They have two functions, to produce male sex-cells (sperms) and to produce the male hormones androgens e.g. testosterone. These are produced by the interstitial cells of testes. Testosterone helps in the development of male secondary sex characters such as growth of hair on the face and thickness or coarseness of voice in males.
Endocrine System – female gonads or Ovaries
Ovaries in female produce oestrogen which controls development of secondary sexual characters (development of breast etc) and causes the lining of uterus to thicken.
Drugs and Nervous System
There are different types of drugs known to us. Many types of drugs known to us. Many of them have medicinal value and are being used by the pharmaceutical industry. But the misuse or abuse can produce serious physiological, behavioral and mental problems in a person. A brief description of some of the common drugs and alcohol are given below:
. Excessive or harmful use of drug is considered drug abuse of substance abuse. Drug abuse is a major problem. It affects people, their families and many other people with whom they interact.
. Most drugs have devastating effect on brain and other part of nervous system and may cause loss of memory and weakening of nerves due to which permanent damage to the coordination mechanism taken place.
Aspirin
It will not be an exaggeration to call it a wonder drug as it has wide ranging effects e.g. it is used as an analgesic (pain-killer), as antipyretic (anti-fever) as anti-inflammatory and is also useful in heart patients as antithrombotic, but its overuse may lead to blood thinning leading to hemorrhage with serious consequences. It is derived from opium.
Morphine
Primarily a pain relieving drug but its abuse affects the central nervous system and is addictive. It can cause constipation and lowering of blood pressure. Since the drug reduces anxiety the user of the drug develops escapist tendencies and gradually loses the confidence to face the realities of life. It can also produce serious allergic reactions, nausea and vomiting.
Heroin
It is the most addictive drug and is produces form morphine by modification in its chemical structure and this has some adverse effects as of morphine. It affects the nervous system adversely and its indiscriminate use can produce drug induced toxicity. Its addiction is extremely difficult to treat.
Cocaine
It affects the mental functioning and behavior of a person causing anxiety. Insomnia irritability and can make the user psychotic. It has been called as the third scrouge of humanity alcohol and heroin.
Marijuana
It is the oldest drug. It is also called charus and hashish. This drug can produce lightened sensation and hallucination. Its high doze results in death. It alters the production of hormones e.g. reproductive hormones, decreasing the production of sperms in man and ovulation in woman. Men may develop fatty enlargement of the breast.
Nicotine
Cigarette smoke contains over 1000 drugs, a large number of which are carcinogenic. The primary among them is nicotine. This drug is least sedative but highly addictive. When taken for the first time, it may cause nausea, vomiting, headache and general weakness. If a pregnant woman smokes, the nicotine damages the placenta, increasing the likelihood of miscarriages, premature births, and damage to the foetus.
Alcohol (Ethyl)
Among the most harmful of drugs, particularly in view of the frequency of its use, is alcohol. It is a central nervous system depressant. It causes temporary loss of body coordination. It is one of the cases of brain, liver and muscle tissue (including heart) damage. Alcohol in the gut also destroys certain vitamins and interferes whit absorption of others leading to severe vitamin deficiencies. It is also associated with an increased risk for cancer. It produces permanent mental and physical birth defects called foetal alcohol syndrome, in children born to alcoholic mothers.
. In addition to addiction, the use of psychoactive drugs can impair the health of individual drug users in other ways. It can also affect their gametes, and thus the development of their children.
The use of alcohol causes stomach ulcers and permanent damage to heart and liver.
Endocrine System – Nervous disorders
Paralysis: It is the partial or complete loss of the power of motion or sensation especially of voluntary motions in some parts of all of the body. This is usually because of a brain stroke in which some part of the brain becomes inactive because of hemorrhage or clotting of a blood vessel in the brain, there by blocking the blood supply to the brain part. It may also be due to some viral toxins as in polio.
Neurosis: A functional mental disorder characterized by combination of anxiety, obsession, phobia depression etc.
Chemical control in plants: As mentioned before the plants respond to various stimuli but their movements as response to stimuli are slow and limited e.g. plants respond to light, gravity, water and chemical stimuli. The chemical substances known as plant hormones are produced within their bodies which bring about a number of responses by the plants. The plants hormones are mainly produced in the growing parts of plants such as tips of roots and shoots. There are no separate hormone producing organs in plants as compared with endocrine glands of animals. In plants hormones are mainly concerned with the growth and are therefore called growth regulators. In animals hormones perform a number of other functions in addition to growth. The following are important plant hormones.
- Auxins
- Gibberellins
- Cytokinins
- Abscisic acid
Auxins are involved in the change of direction of growth of shoots towards light (phototropism), against the force of gravity (negative geotropism) and growth of root toward gravity (positive geotropism). Auxins also stimulate cell elongation in stem, buds and root in certain concentration while the same hormone in light concentration will inhibit such growth.
Gibberellins were discovered by Japanese scientists in 1930s. These hormones induce rapid elongation of stem in plants. Besides this, gibberellins also help in breaking seed dormancy, induce flowering and also induce early fruiting in some plants.
Cytokinins have been found to be useful in developing tissue culture in the presence of Auxins. They also help in the germination of certain seeds, promote fruit development in certain species.
Abscisic acid is a growth inhibitor hormone and induces dormancy in seeds and buds.