Endocrine Glands & Hormones

1.Endocrine glands lack ducts , so called ductless glands.

2. Their secretions are called Hormones – are non nutrient chemicals that act as intercellular messengers & are produced in trace amounts.

3.The hormones are released into blood & are transported to a distant ly located target organ

Human Endocrine system 1.It consists of endocrine glands & hormones.2 .Endocrine glands of our body are- Pituitary Pineal Thyroid Parathyroid Thymus Pancreas Adrenal Gonads- Ovary & testis Gastrointestinal tract Liver Kidney Heart

Sl. gland location Hormones Action

1 Hypothalamus Basal part of forebrain

A) 2Types of hormones produced thatReleasing InhibitingStimulate Inhibit Secretion Secretion of of Pituitaty ant.. Pituitaty Hor. Dopamine Somatostatin Thyrotropin-releasing ------------------hormone (TRH)•Gonadotropin-releasing--------------- hormone (GnRH)

•Growth hormone-releasing hormone

(GHRH)•Corticotropin-releasing hormone (CRH)

•Prolactin H (PRL)

B) Few neurons go & terminate at at post, pituitary storing the hormones produced at its ends.•Vasopressin (ADH)-

•Oxytocin(BIRTH .H /MILK EJECTION H)

PosteriorPituitary Gland

•stimulate the ant.pituitary to produce –

Thyrotropin stimulating hormone (TSH)•Follicle stimulating hormone (FSH)•LH in 0+ /ICSH0↗

Growth hormone

Corticotropin stimulating hormone

Stimulate mammary glands to produce milk

Stimulates reabsorption of water at DCTStimulates contraction Of i)uterine muscles during delivery & ii)mammary glands

Sl. gland location Hormones Action

2 PITUITARY attached to lower part of brain through a stalk

anteriorpituitary glandthyrotropin stimulating hormone (tsh)•follicle stimulating hormone (fsh)•lh (leutinising h)in 0+ /icsh (interstitial cell stimulating H) in 0↗

posteriorpituitary gland

Sl.

gland location Hormones Action

3 Pineal Dorsal side of forebrain

Melatonin Regulates 24 Hr rhythm of our body & in addition metabolism ,pigmentation, menstrual cycle & defence capability

4 Thyroid Either side of trachea

•Tetraiodothyronine /Thyroxine(T4)•Triiodothyronine(T3)

•Thyrocalcitonin(TCT)

•Regulation of BMR ,RBC formation, metabolism of carbohydrates, protrins & fats,Maintenance of water & electrolyte balance•Regulates blood Calcium levels

5 Parathyroid 4 on back side of thyroid

Parathyroid hormone (PTH)

Increases Ca2+ levels in blood & reabsorption of Ca2+ by renal tubules & in digested food , so known as “Hypercalcaemic Hormone”

Sl gland Location Hormones Action

6 Thymus •Dorsal side of the heart & the aorta

•Thymosin •Play a role in differentiation of T-Lymphocytes in cell mediated immunity & production of antibodies in Humoral immunity

7 Adrenal On anterior part of each kidney,has 2 types of tissues- Adrenal Medulla

&

Adrenal Cortex-3 layers-Zona reticularisZona fasciculataZona glomerulosa

2 hormones-Catecholamines (Adrenaline/epinephrine & noradrenaline /nor epinephrine)(Emergency H/ H Of flight or fight)

•CorticoidsGlucocorticoids(Cortisol)

•Mineralocorticoids-Aldosterone•AndrogenicSteroids

•Increase alertness,pupilary dilation, piloerection, sweating, heart beat,respiratory rate, stimulate breakdown of glycogen ,lipids & proteins

•In carbohydrate metabolism-stimulate gluconeogenesis,lipolysis& proteolysis& inhibit utilisation of aminoacids ,inmaintaining cardiovascular system & kidney functions , produce anti-inflamatory reactions ,suppresses immune response,stimulate RBC pProductionRegulate water & electrolyte balance

Growth of axial ,pubic & facial hair

PancreasAdrenal glands

Sl gland Location Hormones Action

8 Pancreas(2 in 1 gland)

•Below stomach-endocrine part(Islet of Langerhans) has 2 types of cells-β cells α cells

Insulin- secreted byβ cells

•Glucagon-secreted by α cells

•Stimulates conversion of glucose to glycogen•(glycogenesis)controls the level of glucose in the blood-act on hepatocytes & adipocytes & increase cellular glucose uptake .So decreased bloodsugar-so called Hypoglycemic Hormone

• hydrolyse glycogen to glucose- ( glycogenolysis ) acts mainly on the liver cells & stimulate glycogenolysis leading to increased bloodsugar-so called Hyperglycemic Hormone

•Prolonged hyperglycemia =Diabetis mellitus

9 Testis In scrotal sacs-Has interstitial cells of Leydig

Androgens-Testosterone

•Regulate development ,maturation & functions of the male accessory sex organs like epididymis , vas deferens ,seminal vesicles ,prostate gl;and urethra ,etc •Stimulate muscular growth ,growth of facial & axillary hair,aggresiveness low pitch voice•Stimulate spermatogenesis•It is an anabolic hormone as it helps in synthesising proteins & carbohydrates.

10 Ovary Abdomen has ovarian follicles that secrete-Estrogen

The ruptured ovarian follicles is converted into Corpus luteum that secrete -Progesterone

•Stimulation of growth & activities of female secondary sex organs,development of growing ovarian follicles ,appearance of 0+ secondary sexual characters,mammary gland development, 0+ sexual behavior.

Supports pregnancy & Stimulates mammary glands to produce milk

Sl TIssues Location Hormones Action

10 Heart •Atrial walls •Atrial natriuretic factors (ANF)

•decreases blood pressure by dilating the blood ves sels

11 Kidney •JGA •Erytropoietin •Stimulates Erytropoiesis(\formation of RBC)

12 Alimentary canal

•Gastroint-estinal Tract

•Gastrin

•Secretin

•Cholecystokinin(CCK)

•Gastric Inhibitory Peotide (GIP)

•Acts on Gastric glands & stimulate secretion of HCL & Pepsinogen • Acts on exocrine Pancreas & stimulate secretion of water & bicarbonate ions•Acts on both Pancres & gallbladder & stimulate secretion of Pancreaticenzymes & bile juice•Inhibits gastric secretion & motility

13 Other tissues

•at most places

•Growth Factors •Essential for normal growth of tissues & their repair / regeneration

Mechanism of Hormone Action1.Hormones produce their effect on target tissues by binding to specific proteins called Hormone Receptors located in the cell membrane of target tissues – membrane bound receptors or the receptors found inside the target cell-intracellular receptors specially the in the nucleus forming Hormone Receptor Complex 2. These receptors are specific to hormone.3. The complex thus formed leads to biochemical changes in the target tissue. Target tissue metabolism & thus physiological functions are regulated by hormones

5.On the basis of the chemical nature , hormones are classified as

i)Peptide , polypep[tide,protein hormones(eg.

Insulin ,glucagon, pituitary H ,hypothalamic H ,etc.) ii)Steroids(eg. Cortisol , testosterone, progesterone) iii)Iodothyronines (eg,Thyroid H ) Iv)Aminoacid derivatives (eg.epinephrine)

8,.There are two mechanisms of hormone action on all target cells.9. Nonsteroid Hormones Nonsteroid hormones (water soluble) do not enter the cell but bind to plasma membrane receptors, generating a chemical signal (second messenger) inside the target cell. Five different second messenger chemicals, including cyclic AMP have been identified. Second messengers activate other intracellular chemicals to produce the target cell response.

10.Steroid Hormones – The second mechanism involves steroid hormones, which pass through the plasma membrane and act in a two step process. Steroid hormones bind, once inside the cell, to the nuclear membrane receptors, producing an activated hormone-receptor complex. The activated hormone-receptor complex binds to DNA and activates specific genes, increasing production of proteins.1 2.