Transcript The Autonomic Nervous System

The Autonomic Nervous
System
Nervous System
Central
Peripheral
Somatic
Control out
Autonomic
Control inside
A.1. The autonomic nervous system:
•
is regulated by the
Hypothalamus
• It regulates activities of :
(1) Visceral muscles : which
are involuntary , and include
(a) cardiac muscle , and
(b) smooth muscle in arterioles
and the gastro-intestinal tract
(GIT) .
(2) Glands ( e.g. , sweat glands
and GIT glands )
•
It consists of 2 subdivisions:
Figure 11-2
Def: Involuntary control of
the visceral organ activities
eg (circulation, digestion,
sweating, papillary size)
Sympathetic
Division:
Parasympathetic
Functional Anatomy
The autonomic nerves consist of two neutrons.
1. Preganglionic: Its cell body is located in the
CNS.
2. Postganglionic: Its cell body in a ganglion
outside the CNS. It innervates the effector organ.
Functional anatomy..cont
Originate in the lateral
horn cells in the spinal
cord.
Sympathetic:
originate in the thoracic
and lumbar regions of
the spinal cord.
(Thoracolumbar)
Parasympathetic:
originate from cranial
nerves (3rd, 7th, 9th,
10th), and sacral spinal
nerves.
(craniosacral)
C3,7,9,10
P
T1-12
L2-3
S2-4
SYMP
P
Site of Ganglia
Both systems are 2 neuron system.
Sympathetic:
Preganglionic fibers are very
short, synapsing with cell
bodies of postganglionic
C°
neurons within ganglia lie in
sympathetic ganglion chain
(sympathetic trunk).
T1 о
Postganglionic fibers originate in T2 о
the ganglion chain terminate on T3 о
the effector organs.
Some preganglionic fibers pass
through the ganglion chain
without synapsing and
terminate later in sympathetic
Pre
collateral ganglia located
halfway between the CNS and
innervated organs.

effector
organ
Post
Site of ganglia
Parasympathetic:
Ganglia are near or within the effector
organs.
Postganglionic fibers are shorter
than Preganglionic
Parasympathetic (Craniosacral ) system :
1. The preganglionic neurons are
located in the CNS.
1. The postganglionic neurons
(located in parasympathetic
ganglia) are either close to or
embedded in their targets tissues .
Functions of the ANS
The ANS controls involuntary visceral
organ activities.
Such as: circulation, digestion, sweating, and
papillary size.
The sympathetic and parasympathetic
systems exert opposite effects.
The sympathetic is activated during stress &
emergencies. Prepare for “fight or flight”.
The parasympathetic is concerned with
vegetative functions (general
housekeeping), eg: feeding, resting and
sexual stimulation.
The ANS has 2 subdivisions :
sympathetic and parasympathetic
Sympathetic
Parasympathetic
ُُEye
Iris
Ciliary ms
Dilatation of pupil
Relaxation (far vision)
Lacrimal glands
non
Costriction of pupil
Contraction
(nearvision)
lacrimation
heart
Peripheral bl vessels
Increase H.R
Increase force of cont
Dilatation of coronary bl
vessl
Vasoconstriction
Vasodilatation of sk ms
lungs
bronchodilation
GIT
Relax of walls &
Const of sphincters
(filling promoted)
Decrease H.R
non
constriction
Increase motility &secretion
Relaxation of sphincters
(emptying promoted)
Sympathetic
Urinary bladder
Sex organs
Relax of walls &
Cont of internal
sphincter
(filling promoted)
ejaculation
Parasympathetic
Cont of walls &
Relax of internal sphincter
(emptying promoted)
Erection of penis
Or clitoris
Figure 113
Figure 112
Chemical or neural transmitter
All preganglionic fibers release acetylcholin (Ach).
All parasympathetic postganglionic release Ach.
All sympathetic postganglionic release
noradrenalin, except sweat glands and blood
vessels in skeletal muscle release Ach.
Ach
Para
Ach
Symp
Ach
Noradrenaline
except sweat gl
bl vessl of skeletal ms)
Chemical Division of ANS
Cholinergic
(Ach)
Adrenergic
(adrenalin&nor)
1. All preganglionic most symp post
ganglionicnoradrenalin.
(para+symp)
Adrenalin
2. All Para Post
Adrenal medulla is a
ganglionic.
modified symp ganglion
3. Symp
that does not give rise to
postganglionic at postganglionic fibers. It
sweat glands and secretes mainly adrenalin
blood vessels in upon stimulation by
preganglionic.
skletal ms.
Ach
Adrenalin
Adrenal Medulla
Chemical transmitters..cont
Chemical transmitters act locally either
at the synapse or at the target cell
receptors.
Their effect lasts only for a few seconds
because they are either destroyed or
removed from the site of their release.
Ach is removed by hydrolysis.
Achcholinesterase cholin+acetate
Noradrenalin is rapidly taken up by the
nerve endings by active transport.
Biosynthesis and reuptake of
noradrenalin
Receptors:
Def: the site on the cell membrane with which
the chemical
transmitter combines to produce its effect on
the cell.
Adrenergic receptors
α is found in :
– Iris
– Blood vessels
– GIT
β is found in :
– Heart
– bl vessel of Skeletal muscle
– GIT
Adrenergic receptors


(1, 2)
Constriction
on blood vessels
2 Dilatation
coronary,bl vessel of
skeletal ms
Bronchial tree
Adrenergic receptors
1. -receptors
Vasoconstrition
Dilatation of pupil
Blocked by phentolamine
2. receptors
1
2
Mainly in heart
H.R.&force
Blocked by atenolol
(hypertention)
In bronchial tree
Cause
bronchodilatation
Stimulated by
salbutamol
(bronchial asthma)
Proprranlol
Blocks both 1& 2
Not useful, C/I in asthmatic people
Cholinergic receptors
Divided into :
Nicotinic ( in all ganglia )
Muscarinic ( in effector tissues )
Cholinergic receptors
Nicotinic
Muscarinic
In ganglia
Stim by small dose of
nicotine
Inhibt by large dose of
nicotine
Not blocked by atropine
Blocked by ganglion
blocker
In target organs
hexamethonium
Blocked by atropine
(for relief of colic&before
surgery to reduce
salivary&bronchial
secretion to prevent
inhaling these secretions)
.
Drugs that you should know
Epinephrine .
Salbutamol ( ventolin ) .
Propranolo ( inderal ) .
Atenolol ( tenormin ) .
Atropine .
Prazosin
Phentolamine
Hexamethonium
Sympathetic (Thoracolumbar):
3.
4.
5.
The neurotransmitter between the preganglionic and the
postganglionic neuron is Ach. The receptors on the postganglionic
neurons are of the cholinergic nicotinic type.
The neurotransmitter secreted by the postganglionic neuron is
NorEpinephrine (NE). The receptors on the target are adrenergic
receptors (alpha or beta).
There is a great divergence. The divergence implies diffuse
adrenergic actions
Parasympathetic (Craniosacral)
3.
4.
5.
6.
The neurotransmitter between the preganglionic and the
postganglionic neuron is Ach. The receptors on the postganglionic
neurons are of the cholinergic nicotinic type.
The neurotransmitter secreted by the postganglionic neuron is Ach.
The receptors on the target are of the muscarinic cholinergic type.
There is little divergence. The ratio (pre/post) = 1/3.
The limited divergence results in more specific cholinergic actions.
Higher control
Sympathetic sys is regulated by neurons
in the Post part of the hypothalamus.
Parasympathetic is regulated by neurons
in the Anterior part of the hypothalamus.
Origin of preganglionic fiber
Sympathetic
Parasympathetic
Thoracic and lumbar
Cranial and scral
Origin of postganglionic fiber Sympathetic ganglion chain
(location of ganglion)
or collateral ganglia
Terminal ganglia (in
or near effectors
organ
Length and type of fiber
Shorter cholinergic
preganglionic fiber, long
adrenergic post-ganglionic
fiber (most)
Long cholinergic
preganglionic fiber,
short cholinergic postganglionic fiber
Types of receptors for
neurotransmitters
, 1, 2
Nicotinic, muscarinic
Dominance
Emergency fight or flight
Relaxed situation
Types of discharge
Mass discharge of whole
system
Involves discrete organ
Difference between Somatic &
Autonomic
Somatic
innervates skeletal muscle.
Control is precise & voluntary.
Neuronal connection located within
CNS.
Mylenated nerves transmit rapid
impulses.
Autonomic
Innervate smooth &cardiac
muscle, gland and viscera.
Control is diffuse & involuntary.
Nonmyelinated postganglionic
nerves conduct slow impulses.
Mylenated preganglionic nerves
conduct rapid impulses.
Stimulation increases or
decreases activity.
Applied Neurophysioloy (1)
Epinephrine :
Stimulates both beta1 and beta2 receptors
Useful in Tt of Asthma
Contraindcated ( C/I ) in Hypertension or Heart
disease . Why ?
Salbutamol (ventolin ) :
Stimlates mainly beta 2 receptors
Used in Tt of Bronchial asthma
Safer than epinephrine . Why ?
Applied Neurophysioloy (2)
Propranolol ( Inderal ) :
Blocks beta1 & beta2
Used in Tt of hypertension
Should not be given to a patient with Bronchial Asthma .
Why ?
Atenolol ( Tenormin ) :
Blocks only beta 1
Used in Tt of hypertension
Safer than Inderal . Why ?
Atropine :
Blocks muscarinic receptors ( of Ach )
Used in Tt of colic