Chemical Coordination and Integration:
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Human Endocrine System:
Pituitary, pineal, thyroid, parathyroid, thymus, pancreas, adrenal and gonad are the endocrine glands while organs like heart, liver, kidney and gastro-intestinal tract also produce hormones. The Hypothalamus: Basal part of diencephalon (forebrain) is the hypothalamus. Hypothalamus contains several groups of neurosecretory cells called nuclei which produce hormones that regulate the synthesis and secretion of pituitary hormones. |
Hypothalamic hormones are of two types: releasing hormones and inhibiting hormones.
Releasing hormones stimulate the release of pituitary hormones, for example, GnRH stimulates the release of gonadotrophins. Inhibiting hormones inhibit the release of pituitary hormones, for example, somatostatin inhibits the release of growth hormone from pituitary gland.
The hormones produced by hypothalamus reaches the anterior pituitary through portal circulatory system (passed through axons and released at the nerve ending). The posterior pituitary is under the direct neural regulation of hypothalamus.
Releasing hormones stimulate the release of pituitary hormones, for example, GnRH stimulates the release of gonadotrophins. Inhibiting hormones inhibit the release of pituitary hormones, for example, somatostatin inhibits the release of growth hormone from pituitary gland.
The hormones produced by hypothalamus reaches the anterior pituitary through portal circulatory system (passed through axons and released at the nerve ending). The posterior pituitary is under the direct neural regulation of hypothalamus.
Endocrine Glands:
(1) Gland: Pituitary gland.
Hormones: Pars distalis secretes:
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(2) a. Gland: Pineal Gland.
b. Location: dorsal side of forebrain.
c. Hormone(s): melatonin.
d. Function(s):
b. Location: dorsal side of forebrain.
c. Hormone(s): melatonin.
d. Function(s):
- maintains 24-hour (diural rhythm) of our body. (Eg. sleep-wake cycle and body temperature).
- Influences metabolism, pigmentation, menstrual cycle and defense capability.
(3) a. Gland: Thyroid Gland.
b. Location:
c. Hormone(s):
b. Location:
- located on either side of the trachea and both lobes are interconnected by a thin flap of connective tissue called isthmus.
- Thyroid gland is composed of follicles and stromal tissues.
c. Hormone(s):
- tetraiodothyronine or thyroxine (T4).
- triiodothyronine (T3).
- thyrocalcitonin (TCT), a peptide hormone.
- tetraiodothyronine and tiiodothyronine are produced by follicular cells.
- Regulation of the Basal metabolic rate, (BMR)
- RBC formation,
- metabolism of carbohydrates, proteins and fats.
- maintenance of water and electrolyte balance.
- thyrocalcitonin (TCT) regulates the blood calcium levels.
(4) a. Gland: Parathyroid gland.
b. Location: back side of the thyroid gland. one pair on each side. c. Hormone (peptide): parathyroid hormone (PTH), a hypercalcemic hormone. d. Functions: increases the blood Ca+2 level by stimulating:
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(5) a. Gland: Thymus gland.
b. Location: dorsal side of the heart and the aorta. c. Hormone (peptide): thymosins. d. Functions: helps in:
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(6) a. Gland: Adrenal Gland.
c. Hormones:
- adrenal gland is composed of two types of tissues: i. inner adrenal medulla and ii. outer adrenal cortex.
- adrenal cortex is divided into three layers : zona recticularis (inner layer), zona fasciculata (middle layer) and zona glomerulosa (outer layer).
c. Hormones:
- adrenal medulla secretes adrenaline or epinephrine and nor-adrenaline or nor-epinephrine collectively called catecholamines, emergency hormones or hormones of Fight and Flight.
- adrenal cortex secretes a group of hormones called corticoids,which includes glucocorticoids (eg. cortisol) and mineralocorticoids (eg. aldosterone). small amount of androgenic steroids are also secreted.
- glucocorticoids: stimulates glyconeogenesis, lipolysis, and proteolysis, and inhibit cellular uptake and utilization of amino acids.
- Cortisol: (i) maintains cardio-vascular system and kidney functions. (ii) produces anti-inflamatory reactions and suppresses the immune response. (iii) stimulates RBC production.
- Aldosterone: (i) stimulates reabsorption of Na+ and water and excretion of K+ and phosphorus ions. (ii) helps in the maintenance of electrolytes, body volume, osmotic pressure and blood pressure.
(7) a. Gland: Pancreas, both exocrine and endocrine.
* endocrine pancreas consists of “Islets of Langerhans”, which is made up of two types of cells: alpha cells and beta cells.
* alpha cells secrete glucagon and beta cells secrete insulin.
b. Location: near the duodenum.
c. Hormones (peptide): glucagon (hyperglycemic) and insulin (hypoglycemic).
d. Function(s):
Glucagon (hyperglycemic) increases blood glucose level by:
* endocrine pancreas consists of “Islets of Langerhans”, which is made up of two types of cells: alpha cells and beta cells.
* alpha cells secrete glucagon and beta cells secrete insulin.
b. Location: near the duodenum.
c. Hormones (peptide): glucagon (hyperglycemic) and insulin (hypoglycemic).
d. Function(s):
Glucagon (hyperglycemic) increases blood glucose level by:
- acting on lever cells (hepatocytes) and reducing the cellular glucose uptake and utilization.
- stimulating glycogenolysis resulting in hyperglycemia.
- stimulating glyconeogenesis resulting in hyperglycemia.
- acting on hepatocytes and adipocides (cells of adipose tissue) enhancing cellular glucose uptake and utilization.
- stimulating glycogenesis resulting in hypoglycemia.
- Prolonged hyperglycemia leads to diabetes mellitus which is associated with loss of glucose through urine and formation of
- harmful compounds known as ketone bodies.
- Treatment: insulin therapy.
(8) a. Gland: Testes
* composed of seminiferous tubules and stromal or interstitial tissues
b. Location: outside the abdomen in sortal sac to lower the temperature.
c. Hormone: interstitial cells or Leydig cells produce a group of hormones called androgen, which contains
mainly testosterone.
d. Function(s):
* composed of seminiferous tubules and stromal or interstitial tissues
b. Location: outside the abdomen in sortal sac to lower the temperature.
c. Hormone: interstitial cells or Leydig cells produce a group of hormones called androgen, which contains
mainly testosterone.
d. Function(s):
- Androgen regulates the growth and activities of the male accessory sex organs.
- Stimulates spermatogenesis (formation of spermatozoa), muscular growth, growth of facial and axillary hair, aggressiveness etc...
9. a. Gland: Ovary.
b. Location: abdomen.
c. Hormone(s): androgen (group of hormones) and progesterone.
b. Location: abdomen.
c. Hormone(s): androgen (group of hormones) and progesterone.
- Ovary contains ovarian follicles and stromal tissues.
- Growing ovarian follicle secrete mainly estrogen.
- corpus luteum- structure formed from raptured follicle after ovulation-secrete progesterone.
- Estrogen regulates the growth and activities of female secondary sex organs, development of growing ovarian follicles.
- Progesterone supports pregnancy and stimulates the formation of alveoli (sac-like structure which stores milk) and milk secretion.
Hormones of Heart, Kidney and Gastrointestinal Tract:
Hormones are also secreted by some tissues which are not endocrine.
1. a. Organ: atrial wall of heart.
b. Hormone(s): atrial natriuretic factor (ANF).
c. Function(s) (peptide): decreases blood pressure being vasodilator.
2. a. Organ: juxtaglomerular cells of kidney.
b. Hormone(s): erythropoietin
c. Function(s) (peptide): stimulates erythropoiesis (RBC formation).
3. a. Organ: endocrine cells of gastrointestinal tract.
b. Hormone(s) (peptide): gastrin, gastric inhibitory peptide, secretin and cholecystokinin (CCK).
c. Function(s):
1. a. Organ: atrial wall of heart.
b. Hormone(s): atrial natriuretic factor (ANF).
c. Function(s) (peptide): decreases blood pressure being vasodilator.
2. a. Organ: juxtaglomerular cells of kidney.
b. Hormone(s): erythropoietin
c. Function(s) (peptide): stimulates erythropoiesis (RBC formation).
3. a. Organ: endocrine cells of gastrointestinal tract.
b. Hormone(s) (peptide): gastrin, gastric inhibitory peptide, secretin and cholecystokinin (CCK).
c. Function(s):
- gastrin: stimulates HCL and pepsinogen secretion.
- gastric inhibitory peptide: inhibits gastric secretion.
- secretin: stimulates exocrine pancreas secretion of water and bicarbonates.
- cholecystokinin: stimulates secretion of bile and pancreatic juice.
Mechanism of Hormone Action:
Based on chemical nature, hormones are divided into 4 groups:
Hormones produce their effect by binding with hormones receptors located in target tissues. Hormone receptors that are located on the membrane of target cells are called membrane-bound receptors and hormone receptors that are located in the target cells are called intercellular receptors. Hormone will bind with receptor leading to formation of hormone-receptor complex, which leads to biochemical change in the target tissue.
Hormones which interact with membrane-bound receptors generate second messagers (AMP, iP3, Ca++ etc) which regulate cellular metabolism. Hormones which interact with intercellular receptors regulate the gene expression by interacting with the genome.
Diagrammatic representation if hormone action:
- peptide hormones ( e.g. insulin, glucagon, pituitary and hypothalamic hormones)
- steroids (e.g. testosterone, progesterone, cortisol)
- iodothyronines (e.g. thyroid hormones)
- amino-acid derivatives (e.g. epinephrine).
Hormones produce their effect by binding with hormones receptors located in target tissues. Hormone receptors that are located on the membrane of target cells are called membrane-bound receptors and hormone receptors that are located in the target cells are called intercellular receptors. Hormone will bind with receptor leading to formation of hormone-receptor complex, which leads to biochemical change in the target tissue.
Hormones which interact with membrane-bound receptors generate second messagers (AMP, iP3, Ca++ etc) which regulate cellular metabolism. Hormones which interact with intercellular receptors regulate the gene expression by interacting with the genome.
Diagrammatic representation if hormone action:
Comments (9)
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On 2014-09-09 13:54:43.357900 by Anonymous
gud
On 2014-08-24 12:02:11.844280 by viru
very very wonderful
On 2014-03-12 11:58:46.087480 by Anonymous
interesting
On 2014-02-09 05:07:40.993440 by Muhib
Very helpful for quick revision... But it has some spelling mistake...
On 2014-01-28 06:19:32.568870 by manand
Nice
On 2014-01-22 01:18:03.559270 by Anonymous
all information was very much helpful.thnks
On 2013-12-03 23:36:14.778500 by bharat
beutiful -smart guide
On 2013-08-09 00:08:37.947640 by vippin vinod
This material is very useful to study rather than wasting time reading the whole text.
On 2013-07-05 22:59:41.644200 by Zaheer mahmood
Nice teach