ENDOCRINE SYSTEM

Endocrine System:- Consists of endocrine (ductless) glands and tissues that

produce regulatory chemicals that are called hormones.

- The endocrine and nervous system work together to control and coordinate all other systems of the body.

Hormones:- Are chemical messengers that have specific regulatory

effects on certain (specific) cells or organs- They are secreted in very small amounts - Released directly into the blood stream by which they

are carried to all parts of the body- The specific tissue acted on by each hormone is called

the target tissue

They are divided into to 2 categories:1. Amino acids compounds all except the sex glands

and adrenal cortex hormones2. Steroids hormones derived from lipids

Regulation of Hormones:

-The amount of each hormone that is secreted is normally kept within a specific range. The concentrate of the hormone itself acts as a break on further secretion of that hormone.-When target tissue becomes too active there is a negative effect on the endocrine gland and it decreases secretary action.-The adrenal cortex hormones are the greatest just before arising.-Female hormones are secreted monthly.

Endocrine Glands:

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1. Pituitary Gland small gland attached to the hypothalamus located in the saddle-like depression of the sphenoid bone just behind the optic nerve crossing. It is divided into 2 parts: Anterior and Posterior Lobe. It releases hormones that affect the workings of other glands. It is controlled by the hypothalamus of the brain. Hormones produced in the anterior pituitary are not released from the gland until the releasing hormones arrive from the hypothalamus. There is a releasing hormone for each hormone produced by the anterior lobe. Posterior lobe is controlled by neural impulses originating in the hypothalamus. Axons take the neuron secretions to the posterior lobe, where they are released and absorbed into the blood. The two types of hormones released by the posterior pituitary gland are the ADH and oxytocin. They are produced in the hypothalamus and stored in the posterior pituitary. Tumors of the pituitary gland can cause gigantism in childhood and acromegaly in adults.

2. Thyroid Gland -Largest of the endocrine glands-Located in the neck just below the larynx and in front of the trachea with 2 lateral lobes-A narrow band called the isthmus connects these 2 lobes. A connective capsule encloses the entire gland.-Two types of hormones are produced to help regulate

metabolism are: 1. Thyroxine (T4) 2. Triiodothyronine (T3)-Each of these hormones has iodine atoms in its makeup-These hormones function to increase the rate of

metabolism in body cells (Increase energy and protein metabolism)-The thyroid gland needs an adequate supply of iodine

in the blood to produce these hormones-Calcitonin - active in calcium metabolism and is

antagonistic (opposite) to the parathyroid glands

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-Goiter an enlargement of the thyroid gland may or may not be

associated with over production of hormone.-an under active thyroid gland causes hypothyroidism-an over active gland cause hyperthyroidism

3. Parathyroid Glands: -located behind the thyroid gland and embedded in its capsule are 4 tiny glands-They secrete PTH (parathyroid hormone) which regulates calcium metabolism along with Calcitonin-PTH promotes the release of calcium from the bone increasing the amount free floating in the blood stream. Also causes kidneys to retain calcium -Calcitonin promotes deposit of calcium into the bones-Disorders: 1.) can cause spasms called Tetany from deficiency of calcium or low calcium concentration in blood. 2.) Kidney stones with excess production and re-absorption by the kidneys. (Kidney stones are calcium deposits)(Excess of calcium in the blood causes kidney stones)

4. Adrenal Glands: -Adrenal or suprarenal glands they are 2 small glands located above the kidneys-Each has a medulla (inner area) and a cortex (outer area)-Hormones produced from the medulla portion are called epinephrine (adrenaline) and the norepinephrine.-Sympathetic nervous system regulates secretion of adrenal medullar hormones.-They are secreted when the body is under stress-Medullar hormones have longer and stronger affects for fight and flight-Hormones of the cortex portion are classified into 3 groups:1. Glucocorticoids maintain the carbohydrate reserve (glycogen) by promoting conversion of amino acids into glucose (the main hormone is Cortisol)

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2. Mineralocorticoids important in regulation of electrolyte balance. They control the re-absorption of sodium and secretion of potassium by kidney tubals. (The main hormone is Aldosterone) 3. Sex hormones androgens, estrogens, and progestin

5. Pancreas :-Organ located posterior of the stomach-An endocrine and exocrine gland-Small groups of specialized cells called Islets of Langerhans make up the endocrine portion and function independently from exocrine portion, which produces pancreatic juices-The most important hormone is insulin, active in transport of glucose across the membrane and inside the cell to be metabolized for energy (ATP) source-Insulin also stimulates the liver to convent glucose in glycogen for storage-Glucagon works with insulin to regulate blood sugar levels-Glucagon is antagonistic to insulin. The glucagon increases the concentration of glucose in the blood and insulin decreases the amount of glucose by feeding it to cells.-Disorder is diabetes mellitus glucose is not available

6. Sex Glands or Gonads: -Ovaries and testes not only produce ova and sperm, which are your sex cells, but are also important endocrine glands.-Needed in development of sexual characteristics-Sex hormone or Androgen is testosterone, estrogen, and progesterone-Progesterone is secreted by an empty follicle after ovum is released helps prepare uterus for embryo pregnancy and milk-The sex hormone assists in normal development of pregnancy, stimulates development and maturation of female sex organs, and second characteristics.

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7. Thymus Gland: -Is a mass of lymph tissue-Lies in the upper part of the chest above the heart-Important in development of immunity-The hormone is Thymosin-It assists in the maturation of T-Cells

8. Pineal Gland: -A small flattened cone-shaped structure-Located posterior to the mid brain and connected to the root of the 3rd ventricle -It produces the hormone Melatonin-Melatonin influences regulation of sleep versus wake cycles (produced during the dark period (night) of each day)

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