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 Nervous System
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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Autonomic Nervous System
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
Sympathetic Nervous System
The sympathetic chain communicates with spinal nerves via rami communicans
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Sympathetic Nervous System
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
Sympathetic Supply to the Head
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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Sympathetic Supply to the Head
Loss of sympathetic supply to the head leads to Horner’s syndrome
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Sympathetic Supply to the Head
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
Sympathetic Nervous System
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
Sympathetic Nervous System
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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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Autonomic Nervous System
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
Parasympathetic Outflows
Postganglionic parasympathetic fibres arising from cranial nerves III, VII, IX & X travel with branches of CN V
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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
Parasympathetic Outflows
(via lesser petrosal nerve)
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Pterygopalatine Ganglion(CN VII)
Parasympathetic Outflows
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
Parasympathetic Outflows
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
Parasympathetic Outflows
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
Autonomic Innervation
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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
Autonomic Innervation
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Different receptors bring about different effects
…………..even the same receptor can have different effects
Autonomic Innervation
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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
Autonomic Innervation
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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
Autonomic Innervation
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