Page 57 - 86 human physiology part-2

Chapter 14

of calcium and phosphate from bone into extracellular fluid. This is accomplished by stimulating
osteoclasts to break down bone structure, thus liberating calcium phosphate into the blood. In this way,
the store of calcium contained in bone is tapped; (3) it increases reabsorption of calcium by the renal
tubules, thereby decreasing urinary calcium excretion; (4) it reduces the reabsorption of phosphate by
the renal tubules.

The first three effects result in a higher extracellular calcium concentration. The adaptive value of
the fourth is to prevent the formation of kidney stones.

If parathyroids are removed accidentally during surgery on the thyroind, there would be a rise in
the phosphate concentration in the blood. There would also be a drop in the calcium concentration as
more calcium is excreted by the kidneys and intestines, and more incorporated into the bone. This can
produce serious disturbances, particularly in the muscles and nerves, which use calcium ions for normal
functioning. Overactivity of the parathyroids, which can result from a tumor on the glands, produces a
weakening of the bones. This is a condition that makes them much more vulnerable to fracturing
because of excessive withdrawal of calcium from the bones.

=Adrenal glands

Adrenal glands are a pair of ductless glands located above the kidneys. Through hormonal
secretions, the adrenal glands regulate many essential functions in the body, including biochemical
balances that influence athletic training and general stress response. The glucocorticoids include
corticosterone, cortisone, and hydrocortisone or cortisol. These hormones serve to stimulate the
conversion of amino acids into carbohydrates which is a process known as gluconeogenesis, and the
formation of glycogen by the liver. They also stimulate the formation of reserve glycogen in the tissues,
such as in the muscles. The glucocorticoids also participate in lipid and protein metabolism. The cortex
of the adrenal gland is known to produce over 20 hormones, but their study can be simplified by
classifying them into three categoreies: glucocorticoids, mineralcorticoids, and sex hormones.

They are triangular-shaped glands located on top of the kidneys. They produce hormones such as
estrogen, progesterone, steroids, cortisol, and cortisone, and chemicals such as adrenalin (epinephrine),
norepinephrine, and dopamine. When the glands produce more or less hormones than required by the
body, disease conditions may occur.

The adrenal cortex secretes at least two families of hormones, the glucocorticoids and mineral
corticoids. The adrenal medulla secretes the hormones epinephrine (adrenalin) and norepinephrine
(noradrenalin).

Adrenal Cortex: The hormons made by the Adrenal Cortex supply long-term responses to stress.
The two major hormons produced are the Mineral Corticoids and the Glucocorticoids. The Mineral
Corticoids regulate the salt and water balance, leading to the increas of blood volume and blood
pressure. The Glucocorticoids are monitoring the ACTH, inturn regulating carbohydrates, protiens,
and fat metabilisum. Resulting into an increase in blood gluclose. Glucocorticoids also reduce the
bodys inflammitory responce.

Cortisol is one of the most active glucocorticoids. It usually reduces the effects of inflammation or
swelling throughout the body. It also stimulates the production f glucose from fats and proteins, which
is a process referred to as gluconeogenesis.

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