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Endocrine Physiology
Lecture 1
INTRODUCTION
• Endocrinology-
is the study of the
endocrine system
...
• Hormones are are biologically active molecules
secreted by endocrine glands or cells into the
bloodstream and targeted toward cells in
another organ
...
- specificity
- receptor
- distribution
Types of chemical messenger system
• Neurotransmitters- released by axon
terminals into synaptic junctions
...
• Endocrine hormones- Released by glands
into the blood to influence the function of
target cells at other locations
• Neuroendocrine hormones- secreted by
neurones into the blood and influence the
function of target cells at other locations
...
• Regulation
This includes the processes by which organisms
respond to stimuli within & around them
...
Regulation is achieved by the
integration of the nervous system & the
endocrine system
...
Endocrine glands
•The principal endocrine glands in the human body
are the hypothalamus, pituitary, thyroid,
parathyroids, adrenals, pancreatic islets, gonads,
and pineal
...
g
...
Chemical Identity of Hormones
1) hormones- synthesized from cholesterol eg adrenal
cortex hormones like aldosterone and cortisol
2) Polypeptide / Protein hormones eg anterior and
posterior pituitary gland hormones, pancreas, parathyroid
3) Derivatives of amino acid tyrosine eg thyroid
hormone ( thyroxine and triiodothyroxine) and
adrenal medullae (epinephrine and norepinephrine)
Hormone Interactions
Synergistic effects
Two hormones act together to produce an effect that
is greater than the sum of their separate effects
...
Antagonistic effects
One hormone opposes the action of another
hormone
...
It is logic then
to classify hoimones according to their solubility
into:
• 1
...
• 2
...
MECHANISM OF ACTION OF
HORMONES
• Hormones of the same class have similar
mechanism of actions
...
• The lipophilic hormone passes easily through
the cell membrane and binds with the receptor
...
• The process of two receptor units coming
together at the two half sites is called
Dimerization
...
g
...
Second messengers
• Some actions of hydrophilic hormones are
carried out and completed on binding of the
hormone to its receptor without the need to
another chemical mediator, activation or
inhibition of ion channels
...
• This mediator starts the reactions of the cell,
response
...
• Accordingly, hormones may be called “first
messengers”
...
Adenylyl Cyclase–cAMP Second
Messenger System
Phospholipase C Second Messenger
System
Methods of study of Hormones
Radioimmunoassay (RIA)
ELISA (enzyme-linked immunosorbent
assay)
• The basic components of an ELISA
...
Each well is precoated
with an antibody (Ab1) that is specific for the
hormone (H) being measured
...
A third antibody (Ab3), which recognizes
Ab2, is then added
...
• The amount of product formed can be
determined using optical methods
...
Any unbound material
is washed out of the well before the addition
of the next reagent
...
Concentrations are
determined using a standard curve