Peripheral and autonomic Nervous system

Dr N. SATHYANARAYANA

Nervous System• Has two divisions

– Central Nervous System– Peripheral Nervous System

• Central Nervous System– It Consists of brain and spinal cord– They are center of integration and control

• Peripheral Nervous System– It is nervous system outside brain and spinal cord

• Consists of:– 31 pairs of Spinal nerves– 12 pairs of cranial nerves – They carry information to and from the spinal

cord and brain

Peripheral Nervous System

Peripheral Nervous System

• 3 kinds of neurons connect CNS to the body– sensory– motor– interneurons

• Motor - connect CNS to muscles and organs

• Sensory - connect sensory receptors to CNS

• Interneurons: they are connections within CNS

SpinalCord

Brain

Nerves

• Sensory -Conducts impulses from receptors to the CNS

• There are two divisions :– Somatic (from skin, skeletal muscles and joints)– Autonomic (from organs in body cavity)

• Motor Division –conducts impulses from CNS to effectors

• There are two divisions :– Somatic – Muscles– Autonomic - Smooth muscle ,cardiac muscle Glands

Peripheral nervous system

Somatic Autonomic

Sympathetic Parasympathetic

1.Somatic System

Autonomic-Somatic Motor Systems

Somatic System

• It includes nerves to and from spinal cord

• Controls muscle movements• Sensory inputs comes from skin , skeletal muscles and

joints

Muscle

MotorNeuron

InterneuronSkin receptors

SensoryNeuron

Brain

2.Autonomic Nervous System

Autonomic Nervous System

• 1.Sympathetic nervous System-“Fight or Flight”• 2.Parasympathetic Nervous System-“Rest and

Digest” • These 2 systems are antagonistic• Typically, we balance these two to keep ourselves in

a state of dynamic balance.

Autonomic nervous system

• Once thought to be self governing • But it is regulated by centers in the brain and

hypothalamus• ANS operation follows reflex arc principal

– At the spinal cord level– At brain stem level

• Higher centers of brain play modulatory role

ANS divisions: A) Sympathetic and B)parasympathetic

A)Sympathetic:

–Thoracolumbar outflow - From T1- L2

CENTRAL NERVOUS SYSTEM

Brain

Spinalcord

SYMPATHETIC

Dilates pupil

Stimulates salivation

Relaxes bronchi

Accelerates heartbeat

Inhibits activity

Stimulates glucose

Secretion of adrenaline,nonadrenaline

Relaxes bladder

Stimulates ejaculationin male

Sympatheticganglia

Salivaryglands

Lungs

Heart

Stomach

PancreasLiver

Adrenalgland

Kidney

B) Parasympathetic: Craniosacral outflow - In III,VII, IX and X cranial

nerves – And in Spinal S2-4

CENTRAL NERVOUS SYSTEMBrain

PARASYMPATHETIC

Spinalcord

Stimulates salivation

Constricts bronchi

Slows heartbeat

Stimulates activity

Contracts bladder

Stimulates erectionof sex organs

Stimulates gallbladder

Gallbladder

Contracts pupil

• Most viscera receive both• Except sweat glands and arrector pili –

supplied by sympathetic • Normally their actions are opposite • ANS efferent's have two neurons • Preganglionic and postganglionic • Preganglionic are in the CNS – relay

on post ganglionic • Postganglionic are in the ganglia –

supply target organs

Autonomic nervous system

• Has a chain of two motor neurons

• Preganglionic neuron• Postganglionic neuron• Conduction is slower due to thinly or unmyelinated axons

Pre-ganglionic

Ganglion

Post-ganglionic

ORGANS

A.Sympathetic nervous system

A)Sympathetic:

–Thoracolumbar outflow - From T1- L2

CENTRAL NERVOUS SYSTEM

Brain

Spinalcord

SYMPATHETIC

Dilates pupil

Stimulates salivation

Relaxes bronchi

Accelerates heartbeat

Inhibits activity

Stimulates glucose

Secretion of adrenaline,nonadrenaline

Relaxes bladder

Stimulates ejaculationin male

Sympatheticganglia

Salivaryglands

Lungs

Heart

Stomach

PancreasLiver

Adrenalgland

Kidney

Sympathetic nervous system • Preganglionic neurons :• Cell bodies in the lateral horn

from T1-L2• Leave via the spinal nerve • Enters ganglia of sympathetic

trunk• End at same level • Or send branches above or

below • Or continue as splanchnic nerves

to end collateral ganglion .• Postganglionic neurons :• Cell bodies are in the ganglia of

the sympathetic chain • Pre vertebral or collateral ganglia• Adrenal medulla

Sympathetic pathway

Sympathetic trunks

• They are two cords on either side of vertebral column

• From base of skull to coccyx

• Contains cell bodies of postganglionic neurons

• There are 31 pairs • Due to fusion number

reduced to 22-23

Cervical portion & Superior cervical ganglion• Has 3 ganglia -Superior ,middle

and inferior cervical ganglia • Superior cervical ganglion is :• Formed by fusion of upper 4

cervical ganglia • Located in front of C2&3 vertebra • Lies posterior to internal carotid

artery• Gives gray rami to C1- 4• Forms plexus over internal and

external carotid arteries • Gives branches to pharynx • Superior cardiac branches

Middle cervical ganglion

• Formed by fusion of 5th and 6th cervical ganglia

• Lies anterior to inferior thyroid artery

• Located at the level of C6

• Communicates with inferior by ansa subclavia

• Gives gray rami to C5-6

• Middle cardiac nerves • Thyroid gland

Inferior cervical ganglion

• Formed by fusion of 7th and 8th cervical ganglia

• Lies anterior to transverse process of 7th cervical vertebra

• The ganglion fuses with the T1 to from the Stellate ganglion

• Gives gray rami to C7 to 8 &T1

• Inferior cardiac branches • Tracheal and pulmonary

branches• Plexus around subclavian

and inferior thyroid arteries

Sympathetic Division of the ANS

White and gray rami• White rami are

– Myelinated preganglionic fibers

– Enter ganglia of sympathetic trunk

– Are limited from T1-L2

• Gray rami are– Non myelinated post

ganglionic fibers– Arise in the ganglia – Each spinal nerve has

one gray rami

Parasympathetic nervous system

B) Parasympathetic: Craniosacral outflow - In III,VII, IX and X cranial

nerves – And in Spinal S2-4

CENTRAL NERVOUS SYSTEMBrain

PARASYMPATHETIC

Spinalcord

Stimulates salivation

Constricts bronchi

Slows heartbeat

Stimulates activity

Contracts bladder

Stimulates erectionof sex organs

Stimulates gallbladder

Gallbladder

Contracts pupil

Parasympathetic nervous system • preganglionic neurons :Cell bodies of preganglionic neurons

are found in the brain stem nuclei

• Of III, VII, IX and X cranial nerves • Lateral horns of S 2-4• Preganglionic are myelinated .• Postganglionic neurons :• Cell bodies are in the peripheral ganglia • They lie close to organ of innervation • They send short postganglionic fiber • They are not myelinated • In the head region there are 4 ganglia

– Ciliary –III CN– Pterygopalatine- VII CN– Submandibular _--VII CN– Otic - IX

The Parasympathetic Division

Figure 15.5

Parasympathetic pathway

Ciliary ganglion

• Preganglionic nucleus : Edinger westphal nucleus

• Course :Occulomotor nerve IIICN

• Enters Ciliary ganglion • Postganglionic : short

ciliary nerves • Supply :

– Sphincter pupillae – Ciliary muscle

Pterygopalatine ganglion• Preganglionic nucleus :

lacrimatory nucleus • Course :

– VII CN– greater petrosal nerve + deep

petrosal nerve – nerve of pterygoid canal – Enters Pterygopalatine

ganglion• Postganglionic fibers :

– Maxillary nerve – zygomatic nerve – Lacrimal nerve

• Supply :– Lacrimal gland – Nasal palatal and pharyngeal

glands

Submandibular ganglion • Preganglionic nucleus :

superior salivatory nucleus • Course : VII CN

– Chorda tympani nerve– Lingual nerve– Enters submandibular

ganglion • Postganglionic fibers :

– Directly – Or branches of lingual nerve

• Supply :– Submandibular gland – Sublingual glands

Otic ganglion

• Preganglionic nucleus : Inferior salivatory nucleus

• Course : IX CN– Tympanic branch of IX CN– Lesser petrosal nerve

– Enters otic ganglion • Postganglionic fibers :

– Auriculotemporal nerve

• Supply :– Parotid gland

Vagus nerve • Preganglionic nucleus : Dorsal nucleus of vagus • Course : vagal branches of

– Pulmonary– Cardiac – Esophageal – Gastric

• Postganglionic nuclei :– Ganglia of pulmonary plexus– Ganglia of cardiac plexus– Aurbach’s and Meissners’ plexus– Ganglia in the wall of viscera

• Postganglionic fibers : – Direct branches

• Supply :– Smooth muscle and glands of respiratory system – Conducting system of heart – Esophagus – Stomach, small intestine, ascending colon and

transverse colon

Sacral outflow • Preganglionic nucleus : gray

column of S2-4 • Course : Pelvic splanchnic

nerves • Postganglionic nuclei :

– Aurbach’s and Meissners’ plexus

– Ganglia in the wall of viscera • Postganglionic fibers :

– Direct branches • Supply :

– Descending colon, sigmoid colon and rectum

– All pelvic organs

Comparison of Peripheral& autonomic

Peripheral Autonomic

Type of control Voluntary Involuntary

Motor pathway Consist of one neuron

Consists of two neurons

Action Always excitatory May be excitatory or inhibitory

Neurotransmitter Acetylcholine Acetylcholine or norepinephrine

Comparison of Sympathetic and parsympathetic

Sympathetic Parasympathetic

Outflow Thoracolumbar T1-L2 Craniosacral III, VII, IX , XCN & S2-4

Postganglionic neuron – location

Sympathetic trunk and pre vertebral ganglia – away from viscera

Outside CNS Near to viscera

Length of fibers Preganglionic fibers – short Postganglionic –long

Preganglionic fibers – long Postganglionic – short

Preganglionic fibers Synapse With many postganglionic neurons and supply many viscera

With few postganglionic neurons that supply single viscous

Comparison of Sympathetic and parsympathetic

Sympathetic Parasympathetic

Neurotransmitter at preganglionic

Acetylcholine Acetylcholine

Neurotransmitter at postganglionic

Noradrenalin But sweat glands & blood vessels – acetylcholine

Acetylcholine

Distribution Whole body Limited to:Head & neck, thorax , abdomen and pelvis

Type of system Fight or flight system Rest and repose system

Distribution

• Sympathetic :– Whole body

• Parasympathetic :– Limited to:– Head & neck– Thorax– Abdomen and

pelvis

Applied anatomy

• Horner's syndrome consists of :

• Miosis – constriction of pupil

• Ptosis – drooping of upper eye lid

• Anhydrosis –loss of sweating

• Enopthalmos- sunken eyeball due to paralysis of orbitalis muscle

• Due to lesion of sympathetic supply to head and neck – e.g. cervical rib

Megacolon • Hirschprung’s disease

• Congenital condition with failure of development of myentric plexus in the distal colon

• Extreme dilatation and hypertrophy of distal colon with retention of fecal mass

Thromboangitis obliterans

• It is an obliterative disease of arteries

• Particularly lower limbs

• Vascular spasm due to sympathetic over activity

• With reduced blood circulation

• Relieved by lumbar sympathectomy

Raynaud’s Disease

• Characterized by constriction of blood vessels

• Provoked by exposure to cold

• Or by emotional stress

Hypertension

• Can result from overactive sympathetic vasoconstriction

Achalasia of the Cardia

• Defect in the autonomic innervation of the esophagus