1st lec on endo physiology by dr roomi
TRANSCRIPT
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ENDOCRINE PHYSIOLOGY
BY
DR. MUDASSAR ALI ROOMI (MBBS, M. Phil.)
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INTERCELLULAR COMMUNICATION
Cell Target Cell
Cell
CellTarget Cell
Target CellNeuron
Hormone
Hormone
Hormone Hormone
Hormone
Hormone
Hormone
Endocrine
Paracrine
Autocrine
Blood
Neuroendocrine
Blood
Interstitial Fluid
Interstitial Fluid
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Endocrine hormones are released by glands or
specialized cells into the circulating blood and
influence the function of cells at another
location in the body.
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Chemical Structure of hormones
There are three general classes of hormones:
1. Proteins and polypeptides2. Steroids
3. Derivatives of the amino acid tyrosine
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Steroid hormones
secreted by the adrenal
cortex (cortisoland
aldosterone), the
ovaries (estrogen andprogesterone), the
testes (testosterone),
and the placenta
(estrogen andprogesterone).
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Adrenal Cortex
Testes
Ovaries
Corpus Luteum
Placenta
Kidney
Cortisol, Aldosterone,
Androgens
Testosterone
Estrogens, Progesterone
Estrogens, Progesterone
Estrogens, Progesterone
1,25-Dihydroxycholecalciferol
GLAND/TISSUE HORMONES
STEROID HORMONES
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Proteins and polypeptides: including
hormones secreted by the anterior and
posterior pituitary gland, the pancreas (insulin
and glucagon), the parathyroid gland
(parathyroid hormone), and many others.
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Hypothalamus
Anterior pituitary
Posterior pituitary
Thyroid
Pancreas
Liver
Parathyroid
TRH, GnRH, CRH
GHRH, Somatostatin,
ACTH, TSH, FSH, LH,
PRL, GH
Oxytocin, ADH
Calcitonin
Insulin,Glucagon,
Somatostatin
Somatomedin C (IGF-1)
PTH
Placenta
Kidney
Heart
G.I. tract
Adipocyte
Adrenal medulla
HCG, HCS or HPL
Renin
ANP
Gastrin, CCK,
Secretin, GIP,
Somatostatin
Leptin
Norepinephrine,epinephrine
Gland/Tissue Hormones Gland/Tissue Hormones
PEPTIDE & PROTEIN HORMONES
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Derivatives of the amino acid tyrosine:
secretedby the thyroid (thyroxine and
triiodothyronine) and the adrenal medulla
(epinephrine and norepinephrine).
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Tyrosine
L-Dopa
Dopamine
tyrosinehydroxylase
Norepinephrine
dopa decarboxylase
dopamine-
hydroxylase
Dopaminergic
Neurons
Thyroid Hormones
Adrenergic
Neurons
Epinephrine
phenylethanolamine-
N-methyltransferase
Thyroid GlandAdrenal Glands
Synthesis of Amine Hormones
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SYNTHESIS & SECRETION OF PEPTIDE HORMONES
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Types of Receptors
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Hormone receptors
The locations for the different types of hormonereceptors are generally the following:
1. In or on the surface of the cell membrane. Themembrane receptors are specific mostly for the
protein, peptide, and catecholamine hormones.2. In the cell cytoplasm. The primary receptors forthe
different steroid hormones are found mainly in thecytoplasm.
3. In the cell nucleus. The receptors for the thyroidhormones are found in the nucleus and are believed tobe located in direct association with one or more of thechromosomes.
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down-regulation of the receptors
can occur as a result of:
(1)inactivation of some of the receptor molecules,
(2) inactivation of some of the intracellular protein signaling
molecules,(3) temporary sequestration of the receptor to the inside of
the cell, away from the site of action of hormones thatinteract with cell membrane receptors,
(4) destruction of the receptors by lysosomes after they are
internalized, or(5) decreased production of the receptors. In each case,
receptor down-regulation decreases the target tissuesresponsiveness to the hormone.
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up-regulation of receptors
Some hormones cause up-regulation of receptors andintracellular signaling proteins by:
1. stimulating greater than normal formation of receptor
2. or intracellular signaling molecules by the protein-manufacturing machinery of the target cell,
3. or greater availability of the receptor for interactionwith the hormone.
When up-regulation occurs, the target tissue becomesprogressively more sensitive to the stimulating effectsof the hormone.
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Cell surface receptors
Most are embedded inplasma membrane
Detect signals fromextracellularenvironment
Three major types are :1. Ion channel linked
receptors (ligandgated and voltagegated)
2. G protein linkedreceptors
3. Enzyme linkedreceptors
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Ligand-gated ion channels:
protein pores that open or close in
response to a chemical signal. Binding changes proteins
shape to allow or block ionflow, such as Na+ or Ca2+.
Ion flow changes theconcentration inside thecell.
e.g Ach gated channels in
the sk. Muscles.
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G-Protein coupled receptors
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Cyclic Adenosine Monophosphate (cAMP) Second
Messenger Mechanism
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Cell Membrane Phospholipid Second Messenger
System
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JAK-STAT PATHWAY
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1. The steroid hormone diffuses across
the cell membrane and enters the
cytoplasm of the cell, where it binds
with a specific receptor protein.
2. The combined receptor proteinhormone then diffuses into or is
transported into the nucleus.
3. The combination binds at specific
points on the DNA strands in the
chromosomes, which activates the
transcription process of specific
genes to form mRNA.
4. The mRNA diffuses into the cytoplasm,
where it promotes the translation
process at the ribosomes to form
new proteins.
Steroid & Thyroid Hormones - Mechanism of Action
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SUMMARY
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SUMMARY