Biology 141Biology 141

The Autonomic Nervous The Autonomic Nervous SystemSystem

Chapter 15Chapter 15

OverviewOverview

The The CNSCNS spinal cordspinal cord brainbrain

The The peripheral nervous peripheral nervous systemsystem sensory-somatic nervous sensory-somatic nervous

systemsystem Responds to the external Responds to the external

environmentenvironment 12 pairs of 12 pairs of cranial nervescranial nerves

and and 31 pairs of 31 pairs of spinal nervesspinal nerves..

autonomic nervous autonomic nervous systemsystem

Responds to the internal Responds to the internal environmentenvironment

Parasympathetic nervous Parasympathetic nervous systemsystem

Sympathetic nervous Sympathetic nervous systemsystem

Divisions of the Nervous Divisions of the Nervous SystemSystem

ANSANS

Function:Function: operates without conscious control.operates without conscious control.

Regulation:Regulation: Control:Control:

hypothalamus and brain stem. hypothalamus and brain stem. receives input from limbic system and other receives input from limbic system and other

regions of the cerebrumregions of the cerebrum

Regulate activity of Regulate activity of smooth muscle, cardiac muscle & certain glandssmooth muscle, cardiac muscle & certain glands

ANSANS

Sensory receptors associated with Sensory receptors associated with interoceptors (receptors that monitor interoceptors (receptors that monitor internal environments)internal environments)

Located in blood vessels, viscera, smooth Located in blood vessels, viscera, smooth musclemuscle

ChemoreceptorsChemoreceptors Baroreceptors monitor BPBaroreceptors monitor BP

Internal pain - anginaInternal pain - angina MechanoreceptorsMechanoreceptors

Monitor vessel stretchMonitor vessel stretch

ComparisonComparisonSOMATIC vs. ANSSOMATIC vs. ANS

SSomatic omatic contains both contains both

sensory and motor sensory and motor neurons.neurons.

input from the input from the special and somatic special and somatic senses.senses.

sensations are sensations are consciously consciously perceived.perceived.

innervate skeletal innervate skeletal muscle to produce muscle to produce conscious, conscious, voluntary voluntary movements.movements.

effect of a motor effect of a motor neuron is always neuron is always excitation.excitation.

ComparisonComparisonSOMATIC vs. ANSSOMATIC vs. ANS

ANSANS contains both contains both

sensory and motor sensory and motor neurons.neurons.

Input from Input from interoceptors.interoceptors.

input not consciously input not consciously perceived.perceived.

may receive input may receive input from somatic senses from somatic senses and special sensory and special sensory neurons.neurons.

regulate visceral regulate visceral activities activities

Effect: exciting or Effect: exciting or inhibiting activities inhibiting activities of cardiac muscle, of cardiac muscle, smooth muscle, and smooth muscle, and glands.glands.

ComparisonComparisonSOMATIC vs. ANSSOMATIC vs. ANS

Somatic motor Somatic motor pathways pathways consist of a consist of a singlesingle motor motor neuronneuron

Autonomic motor Autonomic motor pathways pathways consists of consists of twotwo motor neurons in motor neurons in series series

Motor Neurons in SeriesMotor Neurons in Series

first autonomicfirst autonomic cell body in the CNS cell body in the CNS myelinated axon extends to an autonomic myelinated axon extends to an autonomic

ganglion or adrenal medullae ganglion or adrenal medullae second autonomicsecond autonomic

cell body in an autonomic ganglioncell body in an autonomic ganglion nonmyelinated axon extends to an effector.nonmyelinated axon extends to an effector.

Somatic has 1 motor neuronSomatic has 1 motor neuron

ANS has 2 motor neurons in seriesANS has 2 motor neurons in series

First motor neuron: First motor neuron: preganglionicpreganglionic

Preganglionic neuronPreganglionic neuron cell body in brain or spinal cord cell body in brain or spinal cord axon is myelinatedaxon is myelinated extends to autonomic ganglionextends to autonomic ganglion

Second motor neuron: Second motor neuron: postganglionicpostganglionic

Postganglionic neuronPostganglionic neuron cell body lies outside the CNS in an autonomic cell body lies outside the CNS in an autonomic

ganglionganglion axon is unmyelinated fiber that terminates in axon is unmyelinated fiber that terminates in

a visceral effectora visceral effector

First Neuron terminates in a First Neuron terminates in a ganglion or adrenal medullaganglion or adrenal medulla

Can use either NE or ACh as the neurotransmitterCan use either NE or ACh as the neurotransmitter

ANS Efferent BranchesANS Efferent Branches

The output (efferent) part of the ANS The output (efferent) part of the ANS is divided into two principal parts: is divided into two principal parts: the the sympathetic divisionsympathetic division the the parasympathetic divisionparasympathetic division

Organs that receive impulses from both Organs that receive impulses from both sympathetic and parasympathetic fibers sympathetic and parasympathetic fibers are said to have are said to have dual innervation.dual innervation.

Parasympathetic and Parasympathetic and SympatheticSympathetic

ParasympathetParasympatheticic

SympatheticSympathetic

Dual innervationDual innervation

Dual innervationDual innervation one speeds up one speeds up

organorgan one slows down one slows down

organorgan Sympathetic NS Sympathetic NS

increases heart increases heart raterate

Parasympathetic Parasympathetic NS decreases NS decreases heart rateheart rate

Anatomy of Autonomic Motor Anatomy of Autonomic Motor PathwaysPathways

ComponentsComponents Preganglionic neuronPreganglionic neuron

SympatheticSympathetic ParasympatheticParasympathetic

Autonomic gangliaAutonomic ganglia Postganglionic neuronPostganglionic neuron Autonomic PlexusAutonomic Plexus

Preganglionic NeuronsPreganglionic Neurons

SympatheticSympathetic Also called Also called

thoracolumbar divisionthoracolumbar division Cell bodies in the lateral Cell bodies in the lateral

horns of the gray horns of the gray matter in segments T1-matter in segments T1-T12 and L1-L2T12 and L1-L2

Axons are called the Axons are called the thoracolumbar outflowthoracolumbar outflow

ParasympatheticParasympathetic Also called Also called

craniosacral divisioncraniosacral division Cell bodies in the brain Cell bodies in the brain

stemstem cranial nerve nuclei III, cranial nerve nuclei III,

VII, IX, and XVII, IX, and X Cell bodies in the lateral Cell bodies in the lateral

gray horns of segments gray horns of segments S2-S4S2-S4

Axons are called Axons are called craniosacral outflowcraniosacral outflow

Autonomic GangliaAutonomic Ganglia

SympatheticSympathetic 2 groups2 groups

Sympathetic trunk ganglia Sympathetic trunk ganglia (Vertebral chain ganglia)(Vertebral chain ganglia)

lie in a vertical row on either lie in a vertical row on either side of the vertebral columnside of the vertebral column

Innervate above the Innervate above the diaphragmdiaphragm

Prevertebral ganglia Prevertebral ganglia (collateral)(collateral)

Anterior to vertebral column Anterior to vertebral column close to large arteriesclose to large arteries

Innervate below the Innervate below the diaphragmdiaphragm

Autonomic GangliaAutonomic Ganglia

ParasympatheticParasympathetic 1 group: terminal ganglia1 group: terminal ganglia

Located near or in visceraLocated near or in viscera

Postganglionic NeuronsPostganglionic Neurons

postganglionic postganglionic neuron can be neuron can be branched to branched to receive signals receive signals from multiple from multiple ganglionic ganglionic locations.locations.

Autonomic Plexuses: Autonomic Plexuses: Tangled neural networks that lie along major Tangled neural networks that lie along major

arteries.arteries. Major autonomic Major autonomic

plexusesplexuses Cardiac: supplies the Cardiac: supplies the

heart, heart, Pulmonary: supplies Pulmonary: supplies

the lung, the lung, Celiac (solar): liver, Celiac (solar): liver,

gallbladder, stomach, gallbladder, stomach, pancreas, spleen, pancreas, spleen, kidney, reproductive kidney, reproductive organs organs

Major autonomic Major autonomic plexuses plexuses superior mesenteric: superior mesenteric:

small and large intestines small and large intestines inferior mesenteric: large inferior mesenteric: large

intestines intestines Renal: kidneys and Renal: kidneys and

ureters ureters Hypogastric: pelvic Hypogastric: pelvic

visceraviscera

Structure of the Sympathetic Structure of the Sympathetic DivisionDivision

Preganglionic – Preganglionic – leave spinal cord leave spinal cord through ventral through ventral rootroot

Enter the ganglion Enter the ganglion via the white via the white ramusramus

Synapse with Synapse with postganglionicpostganglionic

Leave via gray Leave via gray ramusramus

Terminates on Terminates on visceral effectorsvisceral effectors

3 Pathways of Sympathetic Fibers3 Pathways of Sympathetic Fibers

Spinal nerve routeSpinal nerve route out same levelout same level

Sympathetic chain Sympathetic chain routeroute up chain & out up chain & out

spinal nervespinal nerve Collateral ganglion Collateral ganglion

routeroute out splanchnic out splanchnic

nerve to collateral nerve to collateral ganglionganglion

Divergence of Sympathetic NeuronsDivergence of Sympathetic Neurons

Divergence: Divergence: 1 preganglionic cell synapses on 1 preganglionic cell synapses on

many postganglionic cellsmany postganglionic cells

Mass activation due to Mass activation due to divergencedivergence multiple target organsmultiple target organs fight or flight response explainedfight or flight response explained

Adrenal glandAdrenal gland modified cluster of postganglionic modified cluster of postganglionic

cell bodies that release epinephrine cell bodies that release epinephrine & norepinephrine into blood& norepinephrine into blood

Horner’s SyndromeHorner’s Syndrome

Sympathetic innervation to one side Sympathetic innervation to one side of the face is lost (mutation, injury, of the face is lost (mutation, injury, or disease).or disease). Affects outflowAffects outflow

Drooping of eyelidDrooping of eyelid Constricted pupilConstricted pupil Lack of sweating Lack of sweating

Structure of the Structure of the parasympathetic divisionparasympathetic division

PreganglionicPreganglionic CranialCranial

As part of a cranial As part of a cranial nervenerve

SacralSacral From ventral root of From ventral root of

spinal nervespinal nerve Terminal gangliaTerminal ganglia

In the walls of visceraIn the walls of viscera PostganglionicPostganglionic

Innervate smooth Innervate smooth muscle and glands of muscle and glands of the visceral wallsthe visceral walls

Parasympathetic Cranial NervesParasympathetic Cranial Nerves

Oculomotor nerveOculomotor nerve ciliary ganglion in orbitciliary ganglion in orbit irisiris

Facial nerveFacial nerve pterygopalatine and submandibular pterygopalatine and submandibular

ganglionsganglions supply tears, salivary & nasal secretionssupply tears, salivary & nasal secretions

GlossopharyngealGlossopharyngeal otic ganglion supplies parotid salivary glandotic ganglion supplies parotid salivary gland

Vagus nerveVagus nerve supply heart, pulmonary and GI tract as far supply heart, pulmonary and GI tract as far

as the midpoint of the colonas the midpoint of the colon

Parasympathetic Sacral NerveParasympathetic Sacral Nerve

Form pelvic Form pelvic splanchnic splanchnic nerves nerves

ANS NeurotransmittersANS Neurotransmitters Classified as either cholinergic or Classified as either cholinergic or

adrenergic neurons based upon the adrenergic neurons based upon the neurotransmitter releasedneurotransmitter released

AdrenergicAdrenergic

CholinergicCholinergic

ANS NEUROTRANSMITTERSANS NEUROTRANSMITTERS

CholinergicCholinergic Produce and release acetylcholine (ACh)Produce and release acetylcholine (ACh)

All sympathetic and parasympathetic All sympathetic and parasympathetic preganglionicpreganglionic

All parasympathetic postganglionicAll parasympathetic postganglionic Only sweat gland sympathetic postganglionicOnly sweat gland sympathetic postganglionic

AdrenergicAdrenergic Produce and release norepinephrin (NE)Produce and release norepinephrin (NE)

Most sympathetic postganglionic Most sympathetic postganglionic neurons(noradrenalin)neurons(noradrenalin)

Cholinergic Neurons Cholinergic Neurons

Excitation or inhibition depending upon Excitation or inhibition depending upon receptor subtype and organ involved.receptor subtype and organ involved.

Cholinergic ReceptorsCholinergic Receptors Cholinergic receptors Cholinergic receptors

integral membrane proteins in the postsynaptic plasma integral membrane proteins in the postsynaptic plasma membrane. 2 types: membrane. 2 types: Nicotinic and muscarinicNicotinic and muscarinic

Activation of Activation of muscarinic receptors muscarinic receptors

excitation or inhibition excitation or inhibition Muscarinic receptors Muscarinic receptors

are found on plasma are found on plasma membranes of all membranes of all parasympathetic parasympathetic effectorseffectors

(viscera, smooth (viscera, smooth muscle)muscle)

Activation of Activation of nicotinic receptors nicotinic receptors

excitation excitation Nicotinic receptors Nicotinic receptors

are found on are found on postsynaptic cells of postsynaptic cells of ANS cells and at NMJANS cells and at NMJ

Adrenergic Neurons Adrenergic Neurons Adrenergic neurons release norepinephrine (NE) )Adrenergic neurons release norepinephrine (NE) )

from postganglionicfrom postganglionicsympathetic neurons onlysympathetic neurons only

Excites or inhibits organsExcites or inhibits organs NE lingers at the synapse until enzymatically inactivatedNE lingers at the synapse until enzymatically inactivated Effects triggered by adrenergic neurons typically are longer Effects triggered by adrenergic neurons typically are longer

lasting than those triggered by cholinergic neurons.lasting than those triggered by cholinergic neurons.

Physiological Effects of the Physiological Effects of the ANSANS

Autonomic ToneAutonomic Tone balance between sympathetic and parasympathetic balance between sympathetic and parasympathetic

activityactivity regulated by the hypothalamusregulated by the hypothalamus

Sympathetic ResponseSympathetic Response Supports rigorous functions and rapid ATP productionSupports rigorous functions and rapid ATP production Fight or flight responseFight or flight response

Parasympathetic ResponseParasympathetic Response Enhances rest and digestive functions, storage of ATPEnhances rest and digestive functions, storage of ATP

Fight or FlightFight or Flight

Alarm reaction Alarm reaction dilation of pupilsdilation of pupils IncreaseIncrease

heart rateheart rate respirationsrespirations BPBP Blood flow to skeletal musclesBlood flow to skeletal muscles Blood sugarBlood sugar

decrease in blood flow to nonessential organsdecrease in blood flow to nonessential organs Long lasting Long lasting

lingering NE in synaptic gaplingering NE in synaptic gap

PathwayPathway Autonomic ReflexesAutonomic Reflexes

ReceptorReceptor Responds to stimuliResponds to stimuli Transduce stimuli to action potentialTransduce stimuli to action potential

Sensory neuronSensory neuron Action potential travels to CNSAction potential travels to CNS

Integrating center (CNS)Integrating center (CNS) Interneurons relay sensory info to motor neuronsInterneurons relay sensory info to motor neurons

HypothalamusHypothalamus Brain stemBrain stem Spinal cordSpinal cord

2 Motor neurons (pre and post ganglionic)2 Motor neurons (pre and post ganglionic) Carries action potential from the CNS to an effector Carries action potential from the CNS to an effector

EffectorEffector Smooth or cardiac muscle, glandsSmooth or cardiac muscle, glands

Autonomic Control by Higher Autonomic Control by Higher CentersCenters

Major control and integration center: hypothalamusMajor control and integration center: hypothalamus

Output toOutput to Brain stemBrain stem

HeartHeart Blood vesselsBlood vessels Salivary glandsSalivary glands swallowingswallowing

Spinal cordSpinal cord IntestinesIntestines bladderbladder

Receives input Receives input fromfrom VisceraViscera OlfactionOlfaction GustationGustation Changes in tempChanges in temp OsmolarityOsmolarity Blood chemistry Blood chemistry

levelslevels Limbic systemLimbic system

DISORDERSDISORDERS

Raynaud’s phenomenonRaynaud’s phenomenon excessive sympathetic stimulation of excessive sympathetic stimulation of

smooth muscle in the arterioles of the smooth muscle in the arterioles of the digitsdigits

Result - vasoconstriction Result - vasoconstriction the digits (fingers and toes) become the digits (fingers and toes) become

ischemic (lack blood) after exposure to ischemic (lack blood) after exposure to cold or with emotional stress.cold or with emotional stress.

Digits may become necroticDigits may become necrotic

Autonomic DysreflexiaAutonomic Dysreflexia

Exaggerated response of sympathetic NS Exaggerated response of sympathetic NS in cases of spinal cord injury above T6in cases of spinal cord injury above T6 Sensory impulses from below the injury are unable to Sensory impulses from below the injury are unable to

ascend to the brainascend to the brain Causes mass stimulation of sympathetic nerves below Causes mass stimulation of sympathetic nerves below

the injurythe injury

ResultResult vasoconstriction which elevates blood pressurevasoconstriction which elevates blood pressure

parasympathetic NS tries to compensateparasympathetic NS tries to compensate slows heart rate, dilates blood vessels above the injuryslows heart rate, dilates blood vessels above the injury Produces a pounding headache, hypertension, flushed skin, Produces a pounding headache, hypertension, flushed skin,

profuse sweating above the injury and cool dry skin belowprofuse sweating above the injury and cool dry skin below can lead to seizure, stroke or heart attackcan lead to seizure, stroke or heart attack