Adrenal glands

Adrenal glands

The pair of ductless glands which are located above the kidneys are commonly known as Adrenal glands. The adrenal glands help in the regulation of many essential functions in the body, which includes biochemical balances that influence athletic training and general stress response. The corticosterone, cortisone, and hydrocortisone or cortisol is included by the glucocorticoids. To stimulate the conversion of amino acids into carbohydrates these hormones plays the great role which is a process known as gluconeogenesis and the formation of glycogen by the liver. It can also stimulate the formation of stored glycogen in the tissues, like in the muscles. In the lipid and protein metabolism, the glucocorticoids also participate. The cortex of the adrenal gland is known to produce over 20 hormones, but it can be studied simply by classifying them into three categories. They are given as glucocorticoids, mineralocorticoids, and sex hormones.

The gland which is located on top of the kidneys is generally triangular in shape. Estrogen, progesterone, steroids, cortisol, and cortisone, and chemicals such as adrenalin (epinephrine), norepinephrine, and dopamine are produced by these glands. The disease conditions may occur when the glands produce more or fewer hormones than required by the body.

At least two types of hormones are secreted by the adrenal cortex. The glucocorticoids and mineral corticoids are the hormones secreted by the adrenal cortex. The hormones epinephrine and norepinephrine are secreted by the adrenal medulla.

Adrenal Cortex:

The Adrenal Cortex makes the hormones which supply long-term responses to stress. The Mineral Corticoids and the Glucocorticoids are the two major hormones produced by this gland. The regulation of the salt and water balance is done by the Mineral Corticoids, which leads to the increase of blood volume and blood pressure in the body. The Glucocorticoids are monitoring the ACTH, which regulates carbohydrates, proteins, and fat metabolism. Which results in an increase in blood glucose in the body. The body inflammatory response is reduced by the glucocorticoids.

One of the most active glucocorticoids is Cortisol. Which usually overcomes the effects of inflammation or swelling of the body surface. The production f glucose from fats and proteins is stimulated by it.

The one of the examples of mineral corticoid is aldosterone. The kidney nephrons are signaled by it to absorb again sodium while potassium secretion occurs. If there is a low level of sodium in the blood, the kidney secretes more renin. This is an enzyme which stimulates the formation of angiotensin from a molecule made from the liver is renin. The aldosterone secretion is stimulated by angiotensin. When it enters the blood the more reabsorption of sodium occurs.

The major mineral corticoid is aldosterone, which stimulates the cells of the distal convoluted tubules of the kidneys that increase reabsorption of sodium and decrease reabsorption of potassium. This, in turn, leads to an increased reabsorption of chloride and water. The insulin and glucagon, are important regulators which regulate the ionic environment of the internal fluid.

The blood pressure can be raised by the renin-angiotensin-aldosterone mechanism when it tends to drop. Different two ways are used for this process. The diameter of blood vessels is decreased by vasoconstrictor which is angiotensin. The blood pressure increases when the size of vessels contracts. The blood passing through the kidney becomes more hypertonic when the sodium is reabsorbed. Water follows the sodium into the hypertonic blood and the process is generally known as osmosis. Which increases the amount of volume in the blood and the blood pressure is also increased.

Adrenal Medulla

The hypothalamus starts nerve impulses that travel the path from the bloodstream, spinal cord, sympathetic nerve fibers to the Adrenal Medulla, which then releases hormones. The effects of these hormones provide a short-term response to stress. Excessive secretion of the glucocorticoids causes Cushing's syndrome, characterized by muscle atrophy or degeneration and hypertension or high blood pressure. Under secretion of these substances produces Addison's disease, characterized by low blood pressure and stress.

The "fight or flight" response are produced by epinephrine and norepinephrine, which is similar to the effect of the sympathetic nervous system. The increase in heart rate, breathing rate, blood flow to most skeletal muscles, and the concentration of glucose in the blood is due to these hormones. The blood flow to the digestive organs are decreased and most digestive processes are decreased.

The male sex hormones (androgens) and lesser amounts of female sex hormones such as estrogens and progesterone, which consist mainly by the adrenal sex hormones. Generally, the sex hormones which are produced by the adrenal cortex are undistinguished due to the low concentration of secretion. The masculinizing or feminizing effects appear when the excess secretion occurs. The virilism of the female is the most common syndrome of this sort.

The Addison's disease would result when there be an insufficient supply of cortical hormones. The excessive excretion of sodium ions characterizes this types of diseases, and hence water, due to lack of mineralocorticoids. The blood glucose level decreases due to a deficient supply of glucocorticoids. The effect of a decreased androgen supply cannot be observed immediately. These symptoms are quickly relieved when the adrenal cortical hormones are injected.

The anterior pituitary hormone generally control the hormonal production in the adrenal cortex directly which is generally called adrenocorticotropic hormone (ACTH).

Very close to the kidneys there lie two adrenal glands. Each adrenal gland is actually a double gland, composed of an inner core like medulla and an outer cortex. They are functionally unrelated to each other.

The two hormones are secreted by the adrenal medulla, which is adrenaline or epinephrine and noradrenaline or norepinephrine, the functions of them are very much similar but not identical to each other. The neural tissue is derived embryologically from the adrenal medulla. It has been likened to an overgrown sympathetic ganglion whose cell bodies do not send out nerve fibers but release their active substances directly into the blood, thereby fulfilling the criteria for an endocrine gland. The adrenal medulla behaves just like any sympathetic ganglion by controlling the epinephrine secretion, and which is dependents upon sympathetic preganglionic fibers stimulation.

The several responses are promoted by epinephrine, almost all of them are helpful in coping with emergencies like the blood pressure rises, the heart rate increases, the glucose content of the blood rises, which is the reason of breakdown of glycogen, the spleen contracts and squeezes out a reserve supply of blood, the clotting time decreases, the pupils dilate, the blood flow to skeletal muscles increase, the blood supply to intestinal smooth muscle decreases and hairs become erect. These adrenal functions, which mobilize the resources of the body in emergencies, have been called the fight-or-flight response. Norepinephrine stimulates reactions similar to those produced by epinephrine but is less effective in conversion of glycogen to glucose.

The significance of the adrenal medulla may seem questionable since the complete removal of the gland causes few noticeable changes; humans can still exhibit the flight-or-fight response. This occurs because the sympathetic nervous system complements the adrenal medulla in stimulating the fight-or- flight response, and the absence of the hormonal control will be compensated for by the nervous system.

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