The nervous system coordinates all body functions and enables adaptation to internal and external changes. It is composed of nerve cells called neurons and supporting cells called neuroglia. The autonomic nervous system regulates involuntary functions like heart rate and respiration. It has three subdivisions: the sympathetic nervous system mobilizes the body during fight or flight, the parasympathetic nervous system enables rest and digestion, and the enteric nervous system controls the gastrointestinal system.

2. The Nervous System
coordinates all body
functions, enabling a
person to adapt to
changes in internal and
external environment .
The Nervous System is
composed mainly of the
nerve cells (neurons) and
supporting cells
(neuroglia) .
The Nervous
System
Classification of The Nervous
System

3. The Autonomic Nervous System is a control system that acts largely
unconsciously and regulates bodily functions such as the heart rate, digestion,
respiratory rate, pupillary response, urination, and sexual arousal . This system is
the primary mechanism in control of the fight-or-flight response.
The critical component of central network involved in homeostasis & adaptation.
3 Subdivisions :
1 . Sympathetic Nervous System : Mobilization & increased metabolism
“fight, flight or fright” or “fight, flight or freeze”
2 . Parasympathetic Nervous System : Routine maintenance “rest &digest”
3 . Enteric Nervous System : The enteric nervous system is the intrinsic nervous
system of the gastrointestinal system. It has been described as "the Second
Brain of the Human Body"
The Autonomic Nervous System

4. Functional Differences Between Sympathetic And
Parasympathetic Nervous System

5. A chemical substance which is released at the end of a nerve fibre by the arrival of a
nerve impulse and, by diffusing across the synapse or junction, effects the transfer of
the impulse to another nerve fibre, a muscle fibre, or some other structure.
Classification Of Neurotransmitter According To Site Of Action :
1. Peripheral Neurotransmitter : Acetylcholine (Ach), Epinephrine , Nor Epinephrine
, Histamine .
2. Central Neurotransmitter : Dopamine , GABA , Glutamate , Aspartate , Serotonin
Etc .
Neurotransmitters

6. Receptors are groups of specialised cells. They can detect changes in the
environment, which are called stimuli, and turn them into electrical impulses.
The autonomic nervous system receptors act as on/off buttons that control the
various sympathetic and parasympathetic effects in the body.
Receptor In Nervous System
Adrenoceptors : The receptors on
which epinephrine (adrenaline ) and nor
epinephrine (nor anrenaline ) act are
called adrenoceptors . Adrenoceptors
are of 2 types . They are :
1 . α – adrenoceptors ( α1 , α2 )
2 . β – adrenoceptors ( β1, β2 , β3 )
Cholinoceptors :
The receptors on which acetycholine
(ach) act are called cholinoceptors .
cholinoceptors are of 2 types . they are:
1. Muscarinic receptors : M1, M2 ,
M3 , M4 , M5 .
2. Nicotinic receptors : Nm , Nn
Sympathetic Receptors Parasympathetic Receptors
Adrenoceptors (α , β ) And Muscarinic Receptors Are G-protein Coupled Receptors .

7. Structures of G-protein
The G-protein is a membrane protein composed of three subunits (α , β and γ ) .
The α subunit possesses GTP-ase activity . The 3 subunits are anchored to the membrane through
attached lipid residues .
Types of G-protein : On the basis of α-GTP .
Target for G-protein :
1 . Adenylyl cyclase enzyme : This enzyme is responsible for cAMP formation . e.G : beta
receptors .
2 . Phospholipase C enzyme : This enzyme is responsible for inositoltriphosphate (IP3) and diacyl
glycerol formation . E. G: M1 and M3 receptors .
3. Ion channels : Particularly ca2+ and K+ channels .E. G : M2 receptors .
G-protein Coupled Receptors

8. When an agonist binds with the G-
protein receptor (GPCR)
GPCR couples with alpha subunit of
the G-protein . This coupling further
causes -
Exchange of GDP (which remain
bound with G-protein) with the
intracellular GTP .
So , an alpha G-GTP complex forms .
•The alpha-GTP complex then dissociates
from the receptors and interacts with a
target protein .
•The remaining free βγ-complex subunit
may interacts with another target protein.
Interaction with target protein may result:
a) Formation of 2nd messenger ( cAMP,
IP3 , DAG )
b) Inhibition of 2nd messenger formation.
c) Regulation of receptor operated ion
channel .
Pharmacological response
Activation of G-protein :

9. Methotramine
Muscarinic Cholinoceptors
Features M1 M2 M3
Location &
Function
Autonomic ganglia:
depolarization
Gastric glands:
Increased secretion
CNS :
learning, memory,
motor function
Heart: Decrease rate,
force Nerve endings:
Decrease ACh release
CNS: tremor,
analgesia Visceral
smooth muscle:
contraction
Visceral smooth muscle:
contraction
Iris: constriction of pupil
Ciliary muscle: contraction
Exocrine glands: secretion
Vascular endothelium:
vasodilatation
Nature Gq protein coupled Gi/G0 protein coupled Gq protein coupled
Transducer
mechanism
IP3/DAG – increase
Ca++ PLA2 increasd
– PG synthesis
K+channel opening,
decreased cAMP
IP3/DAG – increase Ca++
PLA2 increasd – PG synthesis
Agonists Oxotremorine, MCN 343A Methacholine Bethanechol
Antagonists Pirenzepine, Telenzepine Solifenacin, Darifenacin