2. z
Introduction of Autonomic nervous system
Autonomic nervous system is a part of the nervous system that controls and regulates
the internal organs.
The autonomic nervous system controls all involuntary actions and helps to maintain
the constancy of the internal environment.
ANS is also known as visceral or involuntary nervous system. It works through nerves,
ganglia arid plexuses and regulates functions which are not conscious control.
ANS consists of two main parts:
1) Sympathetic nervous system
2) Parasympathetic nervous system
Both these nervous systems have opposite actions.
The sympathetic nervous system has catabolic effects like increase in blood pressure,
contraction of arteries, relaxation of bronchial muscles.
The parasympathetic nervous system has anabolic effects like contraction of pupil,
decrease in blood pressure, increase in the activity of digestive system and GIT
secretions etc
4. z
ADRENERGIC DRUGS AND NERUOTRANSMITTERS
Adrenergic drugs are the agents which directly on the sympathetic nervous system.
Adrenergic drugs are also called as sympathomimetic drugs and these agents mimics
the actions of sympathetic nervous system.
Neurotransmitters are often referred to as the body's chemical messengers. They
are the molecules used by the nervous system to transmit messages between
neurons, or from neurons to muscles.
The neurotransmitters of the adrenergic system belongs to a class-catecholamines.
Epinephrine, Norepinephrine and Dopamine are the principal Neurotransmitters.
Epinephrine (Adrenaline), Nor-Epinephrine (Noradrenaline) and dopamine are the
naturally occurring catecholamines and controls various responses of "fight, flight and
fear" system.
5. z
BIOSYNTHESIS OF NEUROTRANSMITTERS (CATECHOLAMINES)
The biosynthesis of neurotransmitter is
carried out in adrenergic neuron in
CNS, in sympathetic neuron in AND
and in adrenal medulla.
It involves the following steps:
Steps are shown here……..
STORAGE AND RELEASE OF
NEUROTRANSMITTERS
NA is stored in synaptic vesicles or
‘granules’ within the adrenergic nerve
terminal in form of of ATP complex.
These neurotransmitters will release
only when there is increase in the
permeability of the nerve terminal membrane
to Ca2+ because of an action potential.
6. z
Catabolism of catecholamines
Catabolism of catecholamines is mediated
by two main enzymes:
catechol-o-methyltransferase (COMT)
which is present in the synaptic cleft and
cytosol of the cell and monoamine oxidase
(MAO) which is located in the
mitochondrial membrane. Finally we will obtain
the 4-hydroxy-3-methoxyphenyl-glycoaldehyde.
7. z
ADRENERGIC RECEPTORS (alpha and beta)
Adrenergic belong to the class of G-protein coupled receptors (GPCRs).
These receptors have a common structure organisation i.e. molecule has 7alpha helical
transmembrane (TM) spanning domains. It has 3 extracellular and 3 intracellular loops.
G-proteins consist of three subunits α , β and y.
Adrenergic receptors are classified into two types α and β receptors,
α receptors are excitatory in nature and, β receptors are inhibitory in nature.
Functions of α1and α2 receptor are as follows
α1 α2
1.Gland secretion
2.Relaxation of Gut
3.Vaoconstrictim and
contraction of smooth muscls
4, Glycogenolysis in liver
1.Vasoconstriction
2.Platelet aggregation
3.Decrease insulin release
4.Decreases sympathetic flow
5.Inhibits neurotransmitter
release
8. z
ß- receptors are further sub-divided intö and ß1receptor and ß2 receptors.
ß1 receptors are present in Cardiac tissue i.e. Heart and JG cells in Kidney.
ß2 receptors are present in smooth muscle and some gland cells i.e.bronchi,blood
vessels,liver etc.
Functions of ß1 and ß2 receptor are as follows
ß1 ß2
1.Increases force and rate of
contraction of heart muscles
2.Dilates coronary blood vessels
3.Relaxes smooth muscles in the
gastrointestinal tract
4.Lipolysis in kidney liver
5.Renin release from JG cells of
kidney
1. Relaxation of smooth muscles in the
bronchi, uterus and arteries which
supply skeletal muscle
2.Linked with inhibitory responses
