Autonomic Nervous System

• basic anatomy of ANS• ANS vs PNS• divisions of ANS• sympathetic division

• anatomy & function• ANS plexuses• sympathetic response• adrenal gland

• parasympathetic division• anatomy & function

• visceral reflexes• stress & the ANS• referred pain anatomy

PNS

CNS

SensorySomatic & visceral

Motor

Visceral Somatic

SympatheticParasympathetic

Autonomic Nervous System• Visceral sensory & motor system

• Innervates viscera, smooth muscle and glands

• Autonomic = self governed

• Adjusts visceral functions to the body’s needs

• Responsible for visceral reflexes

High BP

DecreaseHeart rate

CN IX

CN X

Somatic efferent innervation

Visceral efferent innervation

ACh

ACh

ACh orNE

Autonomicganglion

ACh = Acetylcholine NE = Norepinephrine

Preganglionic neuron• cell body in brain or spinal cord

(lateral horn) • axon is myelinated• Synapses in ganglion

Postganglionic neuron• cell body in autonomic ganglion• axon is unmyelinated • synapses on visceral effector

Basic anatomy of ANS

• Sympathetic– Speeds up– Fight or flight

• Parasympathetic– slows down– rest & digest

Sympathetic division (thoracolumbar)

– preganglionic neuron cell body in T1-L2 of spinal cord

– Ganglia near spine – connected by a chain (sympathetic chain)– Short preganglionic neuron– Long postganglionic neuron

Parasympathetic division (craniosacral)

– preganglionic neuron cell body in S2-S4 of spinal cord & brainstem

– CN’s III, VII, IX & X– Ganglia in organ wall– Ganglia are not connected– Long preganglionic neuron– Short postganglionic neuron

Sympathetic ganglion

Communicatingrami

Dorsal ramus

Ventral ramus

Anterior (ventral)

Posterior (dorsal)

Anatomy of sympathetic chain

Sympathetic chain in thorax

Sympathetic innervation of the heart brain

Sympathetic pathways

• all this innervation is BILATERAL (right & left)

• sympathetic pathways innervate sweat gland, arrector pili & smooth muscle of blood vessels peripherally

• organ responses?

• sympathetic pathways carry noxious sensory information (except in pelvis)

Adrenalcortex

Adrenalmedulla

Adrenal gland

Cortex = steroid hormones (endocrine system)Medulla = modified sympathetic ganglion• secretes epinephrine (adrenaline) & norepinephrine• innervated by preganglionic sympathetic neurons• products get secreted into bloodstream

Remember a stressful event

• What was that event• List 5 changes that occurred in your body that

you noticed during the event• How long did it take for the stress response to

go away?

Parasympathetic pathwaysCranial nerves: III, VII, IX & XSacral nerves S2-S4

NT = acetylcholine

Also bilateral innervation

Carries most sensory info exceptnoxious stimuli

Plexuses of ANS sympathetic + parasympathetic

• Cardiac plexus

• Pulmonary plexus

• Celiac (solar) plexus

• Superior mesenteric

• Inferior mesenteric

• Hypogastric

LowBP

Increase HRAnd constrict BV

sympathetic

High BP

CN IX CN IX

Decrease HRAnd dilate BV

CN X Vagus

Visceral reflex

Beta adrenergic blockersBlock sympathetic response

vagus

vagus

Asthma• parasympathetic response• bronchospasm• increased gland activity• treat with B2 adrenergic agonists (stimulate sympathetic response)

T1-T4 receive visceral afferents from heart

T1 dermatome

Sensory from skin = greenSensory from heart = red

Referred Pain

• Organ & skin pain fibers travel to the spinal cord together• Organ pain misinterpreted as skin pain (referred pain)– Heart & skin in left arm = spinal nerves T1-T5 – Heart attack (pain) is felt in skin (pain) along left arm & chest

What is STRESS?

Short term “amp” to long term amp

Year after year……

Problems!- hypertension- ulcers- constipation- bladder infections- Raynaud’s- sexual dysfunction