Hormones & Endocrine System

DEFINITION

The endocrine system consists of a group of organs (sometimes referred to as glands of internal secretion), whose primary function is to produce and release hormones directly into the bloodstream. Hormones act as messengers to coordinate the activities of various organs.

Endocrine

The main organs of the endocrine system are:

The hypothalamus

Pituitary gland

The thyroid gland

Parathyroid glands

Pancreatic islands

Adrenal gland

The scrotum

Ovaries.

During pregnancy, the placenta also acts as an endocrine gland.The hypothalamus releases a hormone that stimulates the pituitary; some of which trigger the release of other hormones that suppress pituitary and pituitary hormone release.

Pituitary gland is sometimes called the ruling because the pituitary gland coordinates many functions of other endocrine glands. Some pituitary hormones have direct effects, some others simply controlling the speed of release of hormones by other organs.

Pituitary hormones control the release rate itself through a feedback mechanism, where the other endocrine hormone levels in the blood gives a signal to the pituitary to slow down or accelerate the release of hormones.

Not all of the endocrine glands are under the control of the pituitary; some of them respond, either directly or indirectly, against the concentration of substances in the blood:

Insulin-producing cells of the pancreas respond to glucose and fatty acids

Parathyroid cells respond to calcium and phosphate

Adrenal medulla (part of the adrenal gland) responds to direct stimulation of the parasympathetic nervous system.

Many organs that release hormones or hormone-like substances, but usually not mentioned as part of the endocrine system. Some of these organs produce substances that act only at its disposal, while others do not release their products into the bloodstream.For example, the brain produces various hormones whose effects are primarily confined to the nervous system.

HORMONES

Hormones are substances that are released into the bloodstream from a gland or organ, which affects the activity in the cells. Most hormones are proteins consisting of amino acid chains with different lengths. The rest is a steroid, which is a fatty substance which is a derivative of cholesterol. Hormones in very small amounts can trigger the body's response is very broad.

Hormone bound to receptors on the cell surface or inside the cell.Association between hormone and receptor will accelerate, slow down or alter cell function. In the end hormones control the function of the organ as a whole:

Hormones control the growth and development, reproduction and sexual characteristics

Hormones affect the way the body uses and stores energy

Hormones also control the volume of liquid and water and salt levels in the blood.

Some hormones affect only one or two organs, while other hormones that affect the entire body. For instance, TSH is produced by the pituitary gland and affects only the thyroid gland.While thyroid hormone produced by the thyroid gland, but these hormones affect cells throughout the body. Insulin is produced by pancreatic islet cells and affects the metabolism of sugars, proteins, and fats throughout the body.

ENDOCRINE CONTROL

If the endocrine glands function disorders, the levels of hormones in the blood may be high or low, thereby disrupting body functions. To control the endocrine function, then the release of each hormone should be regulated within the limits of the right.The body needs to feel from time to time if it takes more or less hormones.

The hypothalamus and pituitary gland releases hormones if they feel that the levels of other hormones that control them are too high or too low.

And pituitary hormones into the bloodstream to stimulate activity in the target gland. If the target gland hormone levels in the blood sufficient, then the hypothalamus and pituitary gland to know that stimulation is not required anymore and they stopped releasing hormone. Feedback system can control all the glands that are under the control of the pituitary.

Certain hormones under control of the pituitary has a function that has a specific timetable. For example, a woman's menstrual cycle involves increased secretion of LH and FSH by the pituitary gland of each month. Hormones estrogen and progesterone on the ovaries also had levels have fluctuated each month.

The exact mechanism of control by the hypothalamus and pituitary to bioritmik still can not understand. But it is clear that the organs respond to such a biological clock.

Other factors also stimulate the formation of hormones. Prolactin (hormone secreted by the pituitary gland) causes the milk glands in the breast produce milk. The baby's sucking on the nipple stimulates the pituitary to produce more prolactin. The baby's sucking also increase the release of oxytocin which causes wrinkle milk ducts so that the milk can flow into the baby's mouth.

Such gland and parathyroid gland pakreas island, not under the control of the pituitary. They have their own system to sense whether the body needs more or less hormones. For example, insulin levels increased immediately after a meal because the body has to process sugar from food. If insulin levels are too high, blood sugar levels will drop to very low.

Other hormone levels vary based on reasons that are unclear.Corticosteroid levels and the highest growth hormone found in the morning and lowest at dusk. The reason this happens is not fully understood.