lecture 1 hormones
TRANSCRIPT
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Hormones
PROF. DR. V P SONI
School of Biosciences and BioengineeringIIT BOMBAY
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What are Hormones?
A hormone is a chemical substancethat is secreted into the internal
body fluids by one cell or a group ofcells and has a physiological controleffect on other cells of the body.
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Classification
LOCAL or TROPIC
These hormones havea specific local effects.
Acetylcholinesecreted at the nerveendings
Secretinby theduodenal wall whichincreases waterysecretions of the
pancreas
GENERAL
Secreted by specificendocrine glands
Transported to all partsof the body and causedifferent reactions onall cells or specific cells(target tissue)
GrowthHormonebyanterior pituitary
stimulate all cells Reninsecreted by
kidneys in responseto hypotension affectblood vessels
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Chemical Composition
Three basic types
Steroid Hormones
Most of them derived from cholesterol
Cortisol, Aldosterone, Testosterone, Progesterone,Estrogen.
Derivatives of amino acid Tyrosine Thyroxin, Triidothyronine, Epinephrine, Norepinephrine.
Proteins or Peptides Hormones from anterior pituitary gland, Anti diuretic
hormone, Oxytocin, Insulin, Glucagon, Parathormoneetc.
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Endocrine System
Most of the general hormones are secreted by
the endocrine glands
Endocrine glandsDuct less glands
Functions:
Metabolism and tissue maturation Ion regulation
Water balance
Immune system regulation
Heart rate and blood pressure regulation
Control of blood glucose and other nutrients
Control of reproductive functions
Uterine contractions and milk release
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Endocrine Glands
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Hypothalamus and Pituitary gland
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Hypothalamus and Pituitary gland
The hypothalamus secretes tropic hormones exclusivelyinto the blood vessels within the hypothalamus. Thentravel to anterior pituitary by hypothalamic-hypophysialportal vessels. These tropic hormones are going toaffect the anterior pituitary by their releasing or inhibitingeffects.
Meanwhile, the hypothalamus also produces hormoneswhich are transmitted by nerve signals that terminate in
posterior pituitary gland and cause secretion ofhormones within the posterior pituitary (Oxytocin,Vasopressin or anti-diuretic hormone)
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Hormones secreted by Hypothalamus
affecting anterior pituitary
1. TRH-- Thyrotropin Releasing Hormone
This hormone will affect the anterior pituitary which will then affectthyroid gland activity
2. PIH-- Prolactin Release-Inhibiting HormoneProbably there is also present Prolactin Releasing Hormone;These twohormones will affect the secretion of prolactin from the anterior pituitary
3. CRH-- Corticotropin Releasing HormoneThis hormone affects ACTH release from the anterior pituitary
4. GnRH-- Gonadotropin Releasing HormoneThis hormone will affect the anterior pituitary & cause secretion ofgonadotropic hormnes (Lutieinizing hormone, Follicle stimulatinghormone)
5. GHRH-- Growth Hormone Releasing Hormone6. SS or GHIHSomatostatin or Growth Hormone Inhibiting Hormone
These two hormones affect secretion of growth hormone by the anteriorpituitary
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Pituitary Hormones
Anterior Pituitary
Growth Hormone (GH) Growth of almost all cells and tissues of body
Adrenocorticotropin (ACTH)
Stimulates adrenal cortex to secrete adrenocortical hormones
Thyroid Stimulating Hormone (TSH) Stimulates thyroid gland to secrete thyroxin & triiodothyronine
Follicle Stimulating Hormone (FSH)
Growth of follicles in ovaries/ promotes formation of sperms in
testes Leutenizing Hormone (LH)
Promotes secretion of sex hormones and ovulation
Prolactin
Breast development/ secretion of milk
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Posterior Pituitary
Anti Diuretic Hormone or Vasopressin (ADH)
Causes kidneys to retain water
Deficiency causes Diabetes insipidus
Vasoconstriction to blood pressure
Oxytocin
Uterine contraction during birth process
Milk let-down When baby suckles the nippleand areola of the breast of mother sensory
impluse are transmitted to hypothalamus anddue to reflex action oxytocin and prolactin arereleased ; Oxytocin causes contraction ofmyoepithelial cells of mammary glands alveoliexpressing milk into the ducts
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Thyroid Hormones
Thyroxine (T4) & Tri-ido-thyronine (T3)
Iodine is required to form thyroxin; quantity required is 50 mg iodidespre year or 1mg/wk. Common table salt is iodized with 1 part sodiumiodide per 100,000 parts of sodium chloride.
Functions of thyroid hormone and its effect due to changes in amount
of secretionIncrease in thyroid hormone level called Hyperthyroidism and
decreased levels called hypothyroidism
Increase in transcription of large number of genes
Increase rate metabolism by increasing mitochondria number &
size
Thyroid GlandThyroid stimulating hormone
(TSH) controls thyroid secretion bynegative feedback mechanism
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Thyroid Hormones
Promote growth & development of brain during fetal life & fewyears of postnatal life
Promotes growth in growing children
Increase carbohydrate metabolism Increase fat metabolism, fat stores depleted
Decreases quantity of cholesterol, phospholipids & triglyceridesin plasma
Vitamin need increases due to increased metabolism
Body weight decreased and appetite increased
Vasodilatation, increasing blood flow in body tissues especiallymore in skin to eliminate heat, increase cardiac output and heart
rate, increase strength of heart, slight increase in blood volume. Increased rate and depth of respiration Increased appetite & secretion of digestive juices and motility of
gastrointestinal tract
Increase cerebration so hyperthyroid person has extremenervousness, anxiety complex, extreme worry
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Thyroid Hormones
Slight increase in thyroid hormone makes muscle react with vigor
but excessive quantities cause muscle weakening and less quantitycause muscle to be sluggish & relax
Hyperthyroid person has fine muscle tremors
Hyperthyroid person feel constant tiredness & difficulty in sleeping;in contrast hypothyroid person has extreme somnolence.
In men lack of thyroid hormone cause loss of libido and on otherhand excess amount cause impotence
In women lack of thyroid hormone cause menorrhagia &polymenorrhagia (excessive & frequent menstrual bleeding),decreased libido and excess amount cause oligomenorrhea &occasionally amenorrhea
In hypothyroidism gland increase in size condition called Goiter
Calcitonin
Promotes deposition of Calcium in bones and thereby decreaseCalcium concentration in ECF
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Regulation of Thyroid Hormones (Negative
feedback mechanism)
Hypothalamus
Anterior pituitary gland
Thyroid Gland
T3, T4
TRH
TSH
+ve
+ve
-ve
-ve
Iodide+ve
Somatostatin
-ve
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Parathyroid Hormone
Parathyroid Gland
ParathormoneControls calcium concentration in ECF1. Absorption of Ca through gut
2. Tubular resorption of Ca by kidneys
3. Release of calcium from bones
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Parathyroid & Calcitonin Hormones
(Regulation of Calcium)
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Islets of Langerhans in the Pancreas
Insulin
Secreted by cells of islets ofLangerhans
Promotes glucose entry intomost cells of the body.
Deficiency causes Diabetes
mellitus
Glucagon Secreted by cells Increases the release and synthesis of glucose from the liverinto circulating body fluids
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Adrenal Gland
Adrenal Cortex
Cortisol
Multiple metabolic functions(fats, protein and carbohydrates)
Aldosterone Reduces Sodium excretion by
kidneys
Increases Potassium excretion
Adrenal Medullae Epinephrine/ Nor epinephrine
Constriction of blood vesselsand increase in arterial
pressure
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Hormones of Reproductive System
Testes
Testosterone Stimulate growth of male sex organs
Promotes development of secondary sexualcharacteristics
Ovaries
Estrogen Stimulate development of female sex
organs and secondary sexualcharacteristics
Development of breasts mammaryglands plus deposition of fat around it
Progesterone
Preparation of uterus for pregnancy
Promotes development of secretary
apparatus i.e. lobule alveolar systemof the breast
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