Pharmacology Of Autonomic Nervous System & Chemical Transmission AND DIFFERENT TYPES OF NERVE RECEPTORS

1. Pharmacology
Of Autonomic
Nervous System &
Chemical
Transmission
By Meenali mishra
(M.sc Medical Physiology )

2. INTRODUCTION

3. Some Important Terms
 ANS: The system of nerves and ganglia that
innervates the blood vessels,heart,smooth
muscle,viscera and glands
 Controls their involuntary functions
 Consisting of sympathetic and parasympathetic.
 Neurones involved in the ANS pathway
 Preganglionic
 Postganglionic
• Ganglia
Sympathetic trunk ganglia
Preventral ganglia
Terminal ganglia

4. More Terms
 Afferent neurons:- carry
nerve impulse from the organ to
the CNS.
 Efferent neurons:- carry
impulses from CNS to the
organ
 Neurotransmitters:-
chemicals substances made in
the neurons that are released
when an action potential comes
down the neurons.
 Receptors:- structures
usually proteins that receive
neurotransmitters release from
the axonal terminals of the
neuron.

5. Sympathethic &
Parasympathetic
Nervous system
 Two have opposite actions in many cases
 One activates physiological response and
other inhibits it
 Acc. to older simplifications one is
“excitory”(SNS) and other(PSNS) is
“inhibitory”.
 But overturned due to many exceptions
 Modern characterizations: SNS (quick
response mobilizing system) & PSNS(more
slowly activated dampening system)

6. Neurotransmiters
CHOLINERGIC:- Neurons which
sectrets achtylcholamine
ADRENERGIC:- Neurons which
secrets norepinephrin

7. Neurotransmiters
All preganglionic and postganglionic
parasympathetic neurons secret
acetylcholine
2% of postganglionic sympathetic
secret acetylcholine
These are termed as CHOLINERGIC
98% of postganglionic sympathetic
neurons secret norepinephrin
These neurons termed as
ADRENERGIC.

8. Receptors
 Cholinergic : receptors which receive acetylcholine
 Nicotinic
 Location :skeletal muscle, dendrites of postganglionic neurons,adrenal
medulla
 Mechanism of action direct.
 Na+ ion influx produces depolarization of the membrane therefore excitation
 Examples of action: skeletal muscle contraction, generation of action
potential on postganglionic neuron, stimulation of adrenal gland and
secretion of norepinephrin and epinephrine
 Muscuranic
 Location :effectors innervated by postganglionic parasympathetic neurons,
effectors innervated by postganglionic sympathetic neurons
 Mechanism of action is indirect
 Efflux of K+ ion is reduced ,depolarization results and the effect is excitation.
 If Efflux of K+ ion is increased ,hyperpolarization results and the effect is
inhibition
Sympathetic examples:excitation –Eccrine Sweat Gland
inhibition-Blood vessels in skeletal muscles
Parasympathetic examples:excitation:G.I tract
inhibition: heart ,blood vessels supplying penis and
clitoris

9. Receptors
 Adenergic: receptors which receive norepinephrin (NE)
 Alpha 1:
 Location:blood vessels serving skin,viscera,kidney,and
salivary gland
 Most sympathetic target organ except heart
 Mechanism of action is indirect
 Mode of action:produce depolarization therefore they
are excitatory
 Examples of action:
 Constriction of blood vessels
 Constricts visceral organ sphincters
 Constriction of radial muscle of the iris,which causes
dilationof the pupil of the eye.

10. Receptors
Alpha 2
 Location:blood platelets,exocrine glands
of pancreas,liver
 Mecahnism of action is indirect
 They produce hyperpolarization
therefore they are inhibitory
 Examples of function:
 Inhibition insulin and enzyme secretion
from the pancreas
 Inhibit gall bladder contraction.

11. Receptors
Beta 1
Location: heart
,kidney
Mechanism of action
is indirect
They are excitatory
Examples of action:
increase heart rate
and strength of
contraction
Secretion of renin
from JG cells of
kidney

12. Sympathetic Nervous System
SNS general action is to mobilize body’s
nervous system flight or fight response.
Sympathetic nerves originate inside the
vertebral column, toward the middle of the
spinal cord in the intermediolateral cell column
(or lateral horn)
Beginning at the first thoracic segment of the
spinal cord & are thought to extend to the
second or third lumbar segments.
Because its cells begin in the thoracic & lumbar
regions of the spinal cord, the CNS is said to
have a thoracolumbar outflow.
SNS are composed of two-neuron systems
composed of pre- and post-ganglionic neurons.

13. SNS Divisions
 Cell bodies of
preganglionic
neurons reside
within the CNS &
their axon extends
to specialized
sympathetic
ganglia outside of
the CNS where
they synapse on
postganglionic
neuron cell
bodies.
 axons of these
postganglionic
neurons then