Download - Autonomic Nervous System Dr Richard Tunstall Warwick Medical School GEM 2013

Autonomic Nervous System

Dr Richard Tunstall

Warwick Medical SchoolGEM 2013

Objectives

State and demonstrate the regions of the spinal cord / the brainstem nuclei and the specific spinal and cranial nerves involved sympathetic and parasympathetic nerve outflow from the central nervous system.

Explain the location and structure of the sympathetic chain, and outline the range of patterns of synapse of pre- and post ganglionic sympathetic fibres

Outline the potential causes and consequences of a loss of sympathetic supply to a region/structure (this could be an intentional or unintentional loss)

Describe the route of travel of parasympathetic nerves (with cranial nerves) & name and explain the position of the ganglion at which the pre- and post-ganglionic fibres synapse

Explain the functions of the parasympathetic nerves such that you could explain the consequence of an injury to a given nerve, or deduce the location of an injury from a given set of signs/symptoms

Describe the receptors and neurotransmitters of the peripheral nervous system (somatic and autonomic)

Describe the functions of the autonomic nervous system and explain the differing effects of the receptor types within the sympathetic and parasympathetic nervous systems

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Overview

Parasympathetic nervous system

Slows heart rate (no effect on force)Relaxes blood vesselsSpeeds up GI transitRelaxes sphinctersIncreases salivationBronchoconstrictsConstricts pupil (miosis)Erection

Sympathetic nervous system

Raises heart rateIncreases force of contractionConstricts most blood vesselsSlows GI transitConstricts sphinctersBronchodilatesIncrease sweatingDilates pupil (mydriasis)Secretion of seminal fluid/movement of sperm

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Neurons

Dendrites: receptive projections sensitive to neurotransmitter input

Soma (cell body): metabolic centre

Axon: one-way rapid communication between cell body and axon terminals

Axon Terminals: form connections with other neurons/effector tissue via synapses

Neurons are the functional building blocks of the nervous system

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AT

AT

AT

S

S S

S

Nervous System

Central nervous system Brain, spinal cord, retina & CNII

Peripheral nervous system Spinal & cranial nerves (all except CNII)

Autonomic nervous system (sympathetic & parasympathetic)

Somatic sensory and motor nerves

The nervous system consists of central and peripheral parts

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Motor(Efferent)

Sensory(Afferent)

Somatic motor(Skeletal muscle)

Visceral/Autonomic motor(Organs & vessel)

Somatic sensory(Sensations from somatic tissues)

Visceral sensory(Sensations from organs & vessels)

Nervous System Outflows & Inflows

Spinal nerveMixed nerve containing motor, & sensory neuronsSome contain autonomic neurons

Branchio-motor(Pharyngeal arch muscle)

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Special Visceral sensory(Taste)


Autonomic neurons are classified as pre- and post-ganglionic

Brainstem nucleus / Cell body in lateral horn

Peripheral ganglion

TargetPreganglionic Postganglionic

These nuclei are controlled by descending reticospinal tract neurons. The latter neurons are separate to the pre/post ganglionic classification

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Lateral hornAutonomic (only seen T1-L2 & S2-4)

T1 spinal nerve

L2 spinal nerve

Sympathetic Nervous System

Neurons controlling lateral horn cells (or autonomic brainstem nuclei) arise in the hypothalmus

Sympathetic nerves exit CNS with T1 - L2 spinal nerves THERE ARE NO OTHER EXIT POINTS

Sympathetic chain extends to tip of sacrum

Sympathetic chain extends up to near the skull base

Damage to the spinal cord at VERTEBRAL LEVEL L1 should not affect sympathetic innervation but will affect pelvic parasympathetic nerves

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Sympathetic nerves emerge from the CNS only with spinal nerves T1-L2

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Sympathetic chainRuns on lateral sides of vertebral bodies throughout all vertebral column regions

Rami communicansWhite = preganglionic sympathetic neurons passing into chainGrey = postganglionic sympathetic neurons passing from chain into spinal nerve

Sympathetic chain

Sympathetic ganglia

Don’t forget nerves such as the thoracic & cardiac splanchnic nerves emerge from the sympathetic chain


The sympathetic chain communicates with spinal nerves via rami communicans

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Spinal nerve

Dorsal root ganglionFormed by the cell bodies of sensory neurons

Ventral ramus

Dorsal ramus

White rami communicans - seen between T1-L2 onlyPreganglionic sympathetic neurons passing into chain

Grey rami communicansPostganglionic sympathetic neurons passing back into spinal nerve

Sympathetic chain

ganglion

Grey rami communicans onlyNo white ramus communicans seen before spinal nerve T1 or after L2

The sympathetic chain communicates with spinal nerves via rami communicans

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T1

L2

a) Reticulospinal tract neurons originate in brainstem/hypothalamus

b) Descend to T1 & synapse with preganglionic neuron in lateral horn

c) Exit cord with T1 spinal nerve

d) Travel to sympathetic chain

e) Run up chain to cervical ganglia & synapse with postganglionic neuron

f) Postganglionic neurons enter head as plexus around internal carotid artery

g) Supply face via external carotid artery.

Sympathetic Supply to the Head

Brainstem or spinal cord injury proximal to T1 cord level can affect sympathetic supply to head

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Sympathetic Chain Ganglia in the Neck

Superior cervicalC1-4Near skull base

Middle cervicalC5-6

StellateC7-T1Near lung apex

There are normally x3 sympathetic chain ganglia in the neck

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Causes of damage

Pancoast tumour

Tumour of skull base

Lyphadenopathy

Iatrogenic

Trauma

CN VII

Sympathetic neurons form a plexus around the internal carotid artery which join parasympathetic nerves. Distributed with arterial branches

Run to pterygo-palatine ganglion from which they are distributed

Distributed with branches of CN V

This is the superior cervical ganglion in the neck


Forms deep petrosal nerve which joins parasympathetic greater petrosal nerve

Sympathetic neurons are distributed in the head with cranial nerves and arteries

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Loss of sympathetic supply to the head leads to Horner’s syndrome

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Loss of sympathetic supply to the head leads to Horner’s syndrome

Pupil constriction (miosis)

Vasodilation

Ptosis

Lack of sweating (anhydrosis)

Emerg Med J doi:10.1136/emj.2009.081679

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Causes of damage

Pancoast tumour

Tumour of skull base

Lyphadenopathy

Iatrogenic

Trauma

Raynaud disease with tissue damage

The sympathetic chain or sympathetic nerves can be cut/interrupted to treat certain diseases

http://www.assh.org/Public/HandConditions/Pages/Cold-Hand.aspx

Hyperhidrosis

http://bestpractice.bmj.com/best-practice/monograph/856/resources/image/bp/1.html

Sympathectomy

Review the lecture video resources on MoodleR G Tunstall 2013

http://www.assh.org/Public/HandConditions/Pages/Cold-Hand.aspx

http://bestpractice.bmj.com/best-practice/monograph/856/resources/image/bp/1.html

Sympathectomy

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Sympathectomy for hyperhidrosis


Sympathetic Chain Ganglion

Preganglionic Postganglionic

Pre-aortic Ganglion

Spinal nerves Visceral branchesArterial plexi

Splanchnic nerves

Fibres also travel up and down the chain

Adrenal Medulla

Lateral horn cells

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Chromaffin cells of adrenal medulla release adrenaline (95%) into the blood

Systemic release provides a mechanism for reaching cells with no sympathetic innervation


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Outflow with S2-4 spinal nerves

Note: The S2-4 spinal nerves are formed at the L1/2 vertebral level

Parasympathetic nuclei sit in the brainstem

Outflow with CN III, VII, IX & X

Parasympathetic Outflows

Parasympathetic outflow from the CNS is with x4 cranial nerves and x3 spinal nerves

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Parasympathetic outflow from the CNS is with x4 cranial nerves & 3 spinal nerves(conserve energy, bowel activity, urinate, defecate, erection……)

CN IIICN VIICN IX

CN X

Pelvic splanchnic nervesFrom S2-4 Spinal nerves

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Brainstem nucleus Peripheral ganglion

Emerges with CN III, VII, IX or X Travels with CN V

Target

Preganglionic Postganglionic


Postganglionic parasympathetic fibres arising from cranial nerves III, VII, IX & X travel with branches of CN V

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Parasympathetic nerves in the head are hitchhikers

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Edinger Westphal Nucleus

Superior salivatory nucleus

Inferior salivatory nucleus

Ciliary Ganglion

Pterygopalatine Ganglion

Submandibular Ganglion

Otic Ganglion

With CN III With CN Va

With CN VII(via chorda tympani)

With CN VbWith CN VII(via greater petrosal nerve)

With CN Vc

Eyes Pupil constriction Accommodation

Mucous membranesStructures above the maxillary teethe.g. palate, nasal cavity, sinuses, lacrimal gland

Mucous membranesStructures below the the mandibular teethe.g. sublingual, submandibular glands

Parotid glandWith CN IX With CN Vc

NOTE: POSTGANGLIONIC FIBRES DISTRIBUTED WITH CN V BRANCHES

Dorsal nucleus of vagus

With CN X

Organ-specific ganglia


(via lesser petrosal nerve)

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Pterygopalatine Ganglion(CN VII)


Ciliary Ganglion (CN III)

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Parasympathetic nerves to parotid gland(CN IX)

Parasympathetic nerves to submandibular & sublingual glands (CN VII)

CN V


Otic ganglion

Submandibular ganglion

Submandibular (CN VII supplied) & Otic Ganglia (CNIX supplied)

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Pelvic splanchnic nervesBranch from S2-4 spinal nerves

Autonomic nerve plexiForm around most pelvic organs


The pelvic splanchnic nerves emerge from the S2-4 spinal nerves

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Clinical Problems

Gustatory sweating of the face following parotid surgery/injury

Parasympathetic nerves regrow to innervate the sweat glands muscarinic receptors

No pupil light reflex(direct or consensual)

Unopposed sympathetic action

Loss of parasympathetic pupillary innervation

Frey / Frey-Baillarger syndrome

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AcetylcholineNoradrenaline

(norepinephrine)

There are two principal transmitters in the peripheral nervous system

Autonomic Innervation

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CNS

Somatic efferentACh

SympatheticACh

ACh AChParasympathetic

NA


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There are two principal transmitters in the peripheral nervous system

CNS

The receptors for acetylcholine and noradrenaline

Somatic efferentACh

SympatheticACh

ACh AChParasympathetic

NA

Nicotinic

Nicotinic

Nicotinic

Muscarinic

a or b


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Different receptors bring about different effects

…………..even the same receptor can have different effects


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Receptor Location Effect

α1

Blood vessels Smooth muscle contraction

GI smooth muscleRelaxation

(by hyperpolarisation)

Sphincteric muscle Contraction

α2Presynaptic sympathetic

neuron autoreceptorLimits transmitter release at synapseReduces salivation & insulin release

ß1

Heart

Increased HR, Increased speed of AV node

conductionincreased contraction force

GI smooth muscle Relaxation

ß2 BronchiRelaxation

(respond to adrenaline)

ß3 Adipose tissue Lipolysis


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Receptor Location Effect

M1 Autonomic ganglia EPSP (Ca2+ influx)

M2 Cardiac

Negative chronotropic effects on sinoatrial node, & dromotropic on AV

node & atria(Reduction of Ca2+ influx)

M3

Smooth muscle Contraction e.g. Pupil, GI transit(Ca 2+ influx)

Vascular endothelial cells (circulatory system, penis,

sphincters?)

Vascular smooth muscle relaxation(Ca2+ influx and NO release from endothelial cell – the NO causes

decrease in Ca2+ in vascular myocytes)

Muscarinic receptors are membrane-bound receptors working via G-proteins


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Download - Autonomic Nervous System Dr Richard Tunstall Warwick Medical School GEM 2013

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