Hormones
Hormones are the body’s chemical messengers. They travel in the bloodstream to organs or tissues. Hormones work slowly, over time, and affect various processes, including
- Respiration
- Metabolism
- Reproduction
- Growth and development
- Sensory perception
- Movement
- Sexual development
Hormones are potent. That’s why too little or too much of a specific hormone can be severe.
Laboratory tests may measure the levels of hormones in the blood, saliva or urine. A health care provider may carry out these tests if one has signs of hormonal disorder. Home pregnancy tests are similar, and they test for pregnancy hormones in the urine. Endocrine glands are groups of cells which produce hormones. The major endocrine glands are pituitary, pineal, thymus, thyroid, adrenal glands, and pancreas. The endocrine system comprises of a group of glands that make and secrete hormones that the body uses for various functions. These control several different body functions, including:
- Respiration
- Metabolism
- Reproduction
- Growth
- Sensory perception
- Movement
- Sexual development
Hormones are produced by glands which are sent into the bloodstream to the different tissues in the body. They send signals to the tissues to instruct them what they are supposed to do. When these glands do not produce the right amount of hormones, they develop diseases that can affect many facets of life. Hormones, and they develop conditions that can affect many facets of life.
THE MAIN HORMONE-PRODUCING GLANDS ARE:
- Hypothalamus: The hypothalamus helps to maintain body temperature, moods hunger, and the release of hormones from the other glands; and it also controls thirst, sleep and sex drive.
- Pituitary: It is called the “master control gland,” the pituitary gland controls other glands and produces hormones that trigger growth.
- Parathyroid: This gland is responsible for controlling the amount of calcium in the body.
- Pancreas: This gland produces insulin which helps control the blood sugar levels.
- Thyroid: The thyroid produces hormones associated with heart rate and calorie burning.
- Adrenal: Adrenal glands produce hormones which control cortisol, sex drive and the stress hormone.
- Pineal: This gland produces melatonin, which affects sleep.
- Ovaries: The ovaries secrete oestrogen, testosterone and progesterone, the female sex hormones.
- Testes: the testes produce the male sex hormone, testosterone, and produce sperm in men.
Specific factors that affect endocrine organs include ageing, certain diseases and conditions, stress, the environment, and genetics.
Characteristics of Hormones
Chemical Nature of Hormones:
Chemically, hormones can be classified as either steroids or proteins. All the hormones in the human body, except the sex hormones and those from the adrenal cortex, are proteins or protein derivatives.
Mechanism of Hormone:
Blood carries action hormones throughout the body, but only individual cells are affected. Specific cells that respond to a particular hormone have receptor sites for the hormone. It is a lock and key mechanism. If a key fit the lock, the door opens. If the hormone fits the site of the receptor, it will be affected. If the hormone and the receptor site do not match, there is no response. All cells that have receptor sites for a given hormone are made up of the target tissue for that hormone. In some instances, the target tissue is located in a single gland or organ. In other cases, the target tissue is diffused and scattered throughout the body that leads to many areas being affected. Hormones have a particular effect on target cells by modifying cellular activity. Protein hormones react with receptors on the surface of the cell, and the sequence of events resulting in hormone action is relatively rapid. Steroid hormones usually react with receptor sites inside a cell. Because this method of action involves protein synthesis, it is pretty slow.
Control of Hormone Action:
Hormones are very potent substances, which means that small amounts of hormones can have profound effects on metabolic processes. Because of their potency, the secretion of hormones must be regulated within very narrow limits to maintain homeostasis in the body.
Some negative feedback mechanism controls many hormones. In this type of system, the gland is sensitive to the concentration of the substance it regulates. A negative feedback system causes a reversal of increases and decreases in body conditions to maintain stability or homeostasis. Some endocrine glands are secreting hormones in response to other hormones. The hormones that cause secretion of other hormones are called tropic hormones. A hormone from gland A causes gland B to secrete its hormone. A third method of regulating hormone secretion is by direct nervous stimulation. A nerve stimulus causes gland A to secrete its hormone.
