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Endocrinology
•
The study of hormones, the endocrine system,
and their role in the physiology of the body
• The body’s slow chemical communication
system; a set of glands that secrete hormones
into the blood stream
...
g
...
Most hormones enter interstitial fluid and then the blood stream
...
Both neurotransmitters and hormones exert their effects by binding to
receptors on or in their target cells
...
Functions of Hormones
1
...
Metabolism and energy balance
Contraction of smooth and cardiac muscle fibers
...
Control growth and development
3
...
Help to regulate circadian rhythms
Hypothalamus
Releasing
hormones
Nervous
Anterior pituitary
Posterior pituitary
Thyrotropin
Somatotropin
T3
Adrenal
Cortex
Pancreas
Ovary
Vasopressin
Prolactin
LH
ACTH
Thyroid
FSH
Adrenal
Medulla
Testis
Cortisol
Insulin,
Estradiol Testosterone
aldosterone glucagon,
somatostatin
Muscles
liver
Tissues
Liver,
muscles
Reproductive
organs
Oxytocin
Epinephrine
Mammary
glands
Endocrine and nervous systems
•
Many common aspects:
–
small quantities
–
regulate other cells & tissues
–
act through receptors
–
functional overlap between some hormones &
neurotransmitters
–
excitability
–
both can secrete into blood
Hormones travel via the bloodstream to
target cells
•
•
The endocrine system broadcasts its
hormonal messages to essentially all
cells by secretion into blood and
extracellular fluid
...
11
A cell is a target because it has a specific
receptor for the hormone
Most hormones circulate in the blood, coming into contact with
essentially all cells
...
A target cell
responds to a hormone because it bears receptors for the hormone
...
Hormone can also be classified according to their ways of
communication
...
Paracrine hormones (and other paracrine transmitters) only act on cells in the
immediate vicinity of the cells from which they are released
...
General characteristics of hormone
•
Most hormones are either derived from lipids or
modified from amino acid such as tyrosine
...
-Hormones which are water soluble, bind to the
plasma membrane of the cell and function via secondary
messengers are called protein hormones
...
•
•
•
•
Hormones can also be secreted in the final active form egaldosterone
...
They are present in such small quantities as
nanomole and picomole
...
Hormones
are lost by metabolism and conjugation
...
Different tissue respond differently to a hormone, egglucocorticoids stimulate the breakdown of protein in
Classification of Hormone
Hormones may be classified in many ways based on their
characteristics and functions
...
1
...
Each steroid
hormone is unique due to the presence of different chemical
groups attached at various sites on the four rings at the core of its
structure
...
2
...
The presence of two
benzene rings within a T3 or T4 molecule makes these molecules
very lipid-soluble
...
Nitric oxide (NO) is both a hormone and neurotransmitter
...
Peptide hormone and Protein hormones are amino acid
polymers
...
Examples of peptide hormones are antidiuretic hormone and
oxytocin; protein hormone include human growth hormone and
insulin
...
•
The eicosanoid hormones are derived from arachidionic acid,
a 20 carbon fatty acid
...
The eicosanoids are important
local hormones, and they may act as circulating hormone as
well
...
Group I hormones: These hormone bind to intracellular
receptors to form receptor hormone complex through which their
biochemical functions are mediated
...
In circulation, these hormones possess relatively longer half life
(hours or days)
...
Group-II hormones:
•
These hormones bind to cell surface receptors and
stimulate the release of certain molecules namely the
second messengers, which in turn perform the
biochemical function
...
These hormones are hydrophilic
in nature, usually transported in the free form and
possess short half lives (minutes)
...
– mRNA is synthesized in the nucleus and enters
the cytoplasm and promotes protein synthesis for:
• Enzymes as catalysts
• Tissue growth and repair
• Regulate enzyme function
30
Steroid Hormone Intracellular Actions
31
Steroid Hormone Intracellular Actions
33