Autonomic Nervous System concise and informative

1. AUTONOMIC NERVOUS
SYSTEM
Dr Onaadepo O

2. Nervous system- overview

3. Autonomic nervous system(ANS).
introduction
• Autonomic nervous system(ANS) is a motor or
efferent system which connects the central
nervous system(CNS) with the smooth muscle,
cardiac muscle and glands cells of the body
• It helps to control visceral functions such as blood
pressure, GI motility and secretion, urinary
bladder emptying, sweating, body temperature,
heart rate and several other activities
• Some of these functions are controlled almost
entirely by ANS and some only partially

4. Autonomic nervous system(ANS).
introduction
• Note that,
• when there’s a group of neuron cell bodies
located next to each other in the central
nervous system, the whole thing is called a
nucleus,
• while a group of neuron cell bodies located
outside the central nervous system is called a
ganglion.

5. Autonomic nervous system(ANS).
introduction
• It is a two neuron pathway, there is a ganglion
between the CNS and the effector
• Ratio of preganglionic to post ganglionic
neuron is not one to one
• There are more postganglionic than
preganglionic neurones
• Preganglionic neurones are myelinated
whereas post ganglionic are unmyelinated

6. Autonomic nervous system(ANS).
introduction
• ANS is subdivided into
two divisions
• Parasympathetic
( craniosacral
component)
• Sympathetic
(thoracolumbar
component

7. Functional anatomy of the PSN
• Parasympathetic Nervous
system is associated with 4
of the 12 cranial nerves
and three segments of the
spinal cord region
• Cranial nerves transmitting
preganglionic
parasympathetic fibres are
; cranial nerves III
(Oculomotor) , VII (Facial),
IX (Glossopharygeal) and X
(Vagus)
• Sacral nerves arise from
S2, S3 and S4

8. Functional anatomy of the PSN
• Nuclei associated
with these cranial
nerves are
• Edinger- Westphal
nucleus CN III
• Superior salivary
nucleus CNVII
• Inferior salivary
nucleus IX
• Dorsal motor nucleus
of the vagus X

9. Functional anatomy of the PSN
• Parasympathetic ganglia
between the CNS and the
effector(post ganglionic
neurone) are generally
located near or lie within
the innervated organ
• in the cranial region of the
system, there four ganglia,
the
cilliary,pterygopalatine,
submandibular and otic
• they form pathways to the
eyes, lacrimal glands,
salivary glands and the oral
and nasal mucousae

10. Functional anatomy of PSN
• vagus nerves have a
wide distribution
including the
heart,respiratory
tract,GIT as far as the
proximal colon
• distal colon,
rectum,kidney,bladder
and sexual organs are
supplied by the pelvic
splachnic nerves
• parasympathetic
preganglionic neurons
are relatively long
compared with the post
ganglionic neurons

11. Functional anatomy of the
parasympathetic nervous
system(PSN)

12. Functional anatomy of the
Sympathetic nervous system(SNS)
• Preganglionic cell bodies of
the sympathetic portion of
the ANS are located only in
14 spinal cord segments
between T1 and L2( total of
31c1-c7,t1-t12,li-l5,s1-s5
• preganglionic cell bodies are
located in the
intermediolateral cell column
of the grey matter in the
thoracolumbar region of the
spinal cord

13. Functional anatomy of the
Sympathetic nervous system(SNS)
• sympathetic ganglia are arranged
as two interconnected chains
immediately outside the spinal
cord
• each chain or trunk consist of 22-
23 ganglia extending alongside
the whole length of the spinal
cord
• Collateral ganglia are found at
various points along points along
the abdominal aorta(coeliac,
superior mesenteric and inferior
mesenteric)
• the axons leave through the
ventral roots of the spinal cord
and enter the sympathetic chain
in the white rami
communicantees

14. Functional anatomy of the
Sympathetic nervous system(SNS)
• after this, the
preganglionic sympathetic
fibres may;
 Synapse immediately in a
ganglion
 pass up or down the chain
before synapsing
 not synapse in the chain
but pass through into a
splanchnic nerve to a
collateral ganglion(GIT)
 pass back to the dorsal or
ventral branches of spinal
nerve(blood vessel, sweat
glands, hairs)

15. Functional anatomy of the
Sympathetic nervous system(SNS)
• sympathetic ganglia lie
close to the CNS, the
preganglionic fibres are
relatively short
compared with the
postganglionic fibres

16. Sympathetic nervous system(SNS)

17. Autonomic nervous system

18. Neurotransmitters of the ANS
• Most neurotransmitters released by the
preganglionic fibres in both PSN and SNS is
acetylcholine, transmitter interaction is excitatory
• neurotransmiter at the neuro effector junction in
the parasympathetic is acetylcholine
• neurotransmiter at the neuro effector junction in
the parasympathetic is noradrenaline
• neurotransmiter at the neuro effector junction to
the sweat glands, piloerector muscle and skeletal
muscle arterioles is acetylcholine

19. Neurotransmitters of the ANS
some neurotransmission in the ANS involves
neither adrenergic nor cholinergic pathways
some synapses use more than a single
neurotranmitter(co transmission)
acetylcholine and norepnephrine play important
but not exclusive roles in the ANS
Non classic transmitters can be released at any
level (dopamine, glutamine,glycine, GABA,
Neuropeptides

20. Neurotransmitters of the ANS

21. Receptors of the ANS( Ach receptors)
• Acetylecholine activates two different types of
receptors muscarinic and nicotinic receptors
• It is important to understand the two types of
receptors because knowlege of location and
action is important in clinical medicine where
specific drugs can be used to stimulate or
block one or the other two types of receptors

22. Receptors of the ANS( Ach receptors)
• nicotinic receptors are found in the synapses
between prepanglionic and post ganglionic
neurones of both the sympathetic and
parasympathetic systems and also in the
membranes of skeletal muscle at the
neuromuscular junction
• nicotinic receptors on post ganglionic
autonomic ganglia are N2 type, N1 are found
at the neuromuscular junction
• N1 and N2 can be stimulated by nicotine and
Ach(parasympathomimetics)
• N1 can be blocked by curare, N2 can be
blocked by hexamethonium

23. Receptors of the ANS( Ach receptors)
• muscarinic receptors are found in all effector
cells stimulated by post ganglionic neurons of
the parasympathetic nervous system and post
ganglionic cholinergic neurons of the
sympathetic system
• they exist in five subtypes M1-M5
• muscarinic receptors can be stimulated by
muscarine, acetylcholine and can be blocked
by atropine

24. Receptors of the ANS (
Adrenergic receptors)
• Noradrenaline [NA] interacts with two types of
receptors:
• Alpha-adrenergic receptors [alpha adrenoceptors]
• Alpha-1 – blood vessels
• Alpha-2 – CNS (presynaptic)
• Beta-adrenergic receptors [beta adrenoceptors]
• Beta-1 – heart
• Beta-2 – lungs
• Beta-3 – bladder

25. Receptors of the ANS
(Adrenergic receptors)

26. Receptors of the ANS
(Adrenergic receptors)

27. Receptors of the ANS
( Adrenergic receptors)
• type of receptor present and action of drugs that
mimick the action of noradrenalin on sympathetic
effector organs(sympathomimetic drugs)
determine their effects in variuos tisssues
• adrenalin excites mainly alpha receptors but excites
beta receptors slightly
• adrenaline excite both receptors
• isoproterenol has an extremely strong action on
beta but not on alpha
• adrenergic receptors subtypes have a tissue
specific distribution

28. Functions of the Autonomic Nervous
System
• stimulation of sympathetic and
parasympathetic nerves innervating the same
organ elicit opposite responses
• ANS functions spontaneosly, usually at the
subconscious level
• Stimulation of the PNS is responsible for the
rest and digest actions of the body

29. Functions of the Autonomic Nervous
System
• Genaral stimulation of the SNS is responsible
for the fight or flight responses of the body
and originates from thoracolumbar segments
of the spinal cord.
• These actions are most apparent when the
body is faced with stressful situations. It is
designed to mobilise energy stores, allowing
us to cope with the stress and increase our
chances of survival.

30. FUNCTIONS OF SYMPATHETIC AND
PARASYMPATHETIC ACTIVITY

31. FUNCTIONS OF SYMPATHETIC AND
PARASYMPATHETIC ACTIVITY

32. FUNCTIONS OF SYMPATHETIC AND
PARASYMPATHETIC ACTIVITY

33. Comparison between SNS and PSN
Feature Sympathetic NS Parasympathetic NS
Summary of responses Fight or flight Rest and digest
Spinal cord distribution Thoracolumbar Craniosacral
Preganglionic neurone Short Long
Preganglionic
neurotransmitter
Acetylcholine (Ach,
cholinergic)
Acetylcholine (Ach,
cholinergic
Postganglionic neurone Long Short
Postganglionic
neurotransmitter
Noradrenaline (NA,
adrenergic) in most
cases
Acetylcholine (Ach,
cholinergic)

34. Control of ANS functions
• Although the ANS, can function independently, it can
be influenced by brainstem nuclei ,Spinal cord and
sometimes the forebrain(hypothalamus,amygdala
prefrontal cortex, insula,others)
• Nuclei within the lower brainstem mediate
autonomic reflexes(CVS, RS GIT, UGS) or modulate
the general level of autonomic tone
• Hypothalamus in the forebrain cordinates autonomic
function with feeding, thermoregulation,
waterbalance,emotions,sexual drive, reproduction
motivativation

35. ANY QUESTION?