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Review of Peripheral NervousReview of Peripheral Nervous

SystemSystem

Dr. Syed Atif Abbas

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Course ObjectivesCourse Objectives

To describe the functions of theTo describe the functions of the

peripheral nervous system.peripheral nervous system.

To relate the organizational structures ofTo relate the organizational structures ofthe peripheral nervous system to theirthe peripheral nervous system to their

functionsfunctions

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To elaborate on the synthesis of theTo elaborate on the synthesis of the

neurotransmitter involve.neurotransmitter involve.

To describe the effects that affects theTo describe the effects that affects theperipheral nervous system.peripheral nervous system.

To describe the drugs that affects theTo describe the drugs that affects the

peripheral nervous system, their clinicalperipheral nervous system, their clinical

uses and side effects.uses and side effects.

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Course SynopsisCourse Synopsis

OrganizationOrganization andand functionsfunctions of of thethe

peripheralperipheral nervousnervous systemssystems.. ClassificationClassification

ofof thethe peripheralperipheral nervousnervous systemssystems..IntroductionsIntroductions toto drugsdrugs thatthat actact onon thethe

peripheralperipheral nervousnervous systemsystem..

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Course OutlinesCourse Outlines

Structure and functions of neurons,Structure and functions of neurons,

ganglion, synapse, neuroganglion, synapse, neuro-- effectoreffector

junctions.C

oncept, definition, process andjunctions.C

oncept, definition, process andmechanism of membrane potential.mechanism of membrane potential.

Autonomic and somatic nervous systems.Autonomic and somatic nervous systems.

The various receptors involved inThe various receptors involved in

producing responses.producing responses.

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Structure, organization and regulation ofStructure, organization and regulation ofthe adrenergic, cholinergic and somaticthe adrenergic, cholinergic and somaticnervous systems. Neuronervous systems. Neuro-- effectoreffector

mechanism. Interaction and integration ofmechanism. Interaction and integration ofthe systems. Introduction to thethe systems. Introduction to thepathophysiology of diseases that arepathophysiology of diseases that arerelated to the peripheral nervous systemsrelated to the peripheral nervous systemse.g myasthenia gravis, autonomice.g myasthenia gravis, autonomicneuropathy, hypertension, hypotension,neuropathy, hypertension, hypotension,pheochromocytoma and bronchial asthma.pheochromocytoma and bronchial asthma.

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IntroductionIntroduction toto drugsdrugs thatthat actact onon thethe

peripheralperipheral nervousnervous systemssystems withwith regardregard toto

theirtheir mechanismmechanism ofof action,action, metabolism,metabolism,sideside-- effects,effects, structurestructure activityactivity

relationshipsrelationships andand clinicalclinical usageusage..

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TopicsTopics

A review of the peripheral nervousA review of the peripheral nervous

systems.systems.

Organization of the peripheral nervousOrganization of the peripheral nervoussystems.systems.

Neurotransmitters of the peripheralNeurotransmitters of the peripheral

nervous systems.nervous systems.

Neurotransmitter chemistry of theNeurotransmitter chemistry of the

cholinergic system.cholinergic system.

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Neuromuscular transmission.Neuromuscular transmission.

Neuromuscular blockers.Neuromuscular blockers.

Cholinergic / cholinomimetic agents.Cholinergic / cholinomimetic agents.Anticholinesterases.Anticholinesterases.

Antimuscarinic agents.Antimuscarinic agents.

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TheThe neurochemistryneurochemistry ofof thethe adrenergicadrenergicsystemsystem..

The ganglion blockers.The ganglion blockers.

The adrenergic neuron blockers.The adrenergic neuron blockers.

Sympathomimetic agents.Sympathomimetic agents.

Alpha agonist.Alpha agonist.

AlphaAlpha--blockersblockers

Beta agonist.Beta agonist.

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Beta blockersBeta blockers

Imidazoline system.Imidazoline system.

Imidazoline agonists.Imidazoline agonists.

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Recommended BooksRecommended Books

Foster,Foster, RR..W,W, ((19961996)) BasicBasic PharmacologyPharmacology

Stringer,Stringer, JJ..L,L, (( 20012001)) BasicBasic conceptsconcepts inin

PharmacologyPharmacology (( 22ndnd eded..)) NewNew YorkYork:: McMcGrawGraw--HillHill CompaniesCompanies..

TextText BookBook of of MedicalMedical PhysiologyPhysiology byby

GuytonGuyton andand HallHall..

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Review of Peripheral NervousReview of Peripheral NervousSystemSystem

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The Nervous SystemThe Nervous System

A network of billions of nerve cells linkedA network of billions of nerve cells linked

together in a highly organized fashion totogether in a highly organized fashion to

form the rapid control center of the body.form the rapid control center of the body.Functions include:Functions include:

Integrating center for homeostasis,Integrating center for homeostasis,

movement, and almost all other bodymovement, and almost all other bodyfunctions.functions.

The mysterious source of those traits that weThe mysterious source of those traits that we

think of as setting humans apart from animalsthink of as setting humans apart from animals

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Basic Functions of the Nervous SystemBasic Functions of the Nervous System

1.1. SensationSensationMonitors changes/events occurring in and outside theMonitors changes/events occurring in and outside the

body. Such changes are known asbody. Such changes are known as stimulistimuliand the cellsand the cells

that monitor them arethat monitor them are receptorsreceptors..

2.2. IntegrationIntegrationThe parallel processing and interpretation of sensoryThe parallel processing and interpretation of sensory

information to determine the appropriate responseinformation to determine the appropriate response

3.3. ReactionReactionMotor output.Motor output.

The activation of muscles or glands (typically via the releaseThe activation of muscles or glands (typically via the release

ofofneurotransmittersneurotransmitters (NTs))(NTs))

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Nervous vs. Endocrine SystemNervous vs. Endocrine System

Similarities:Similarities:

They both monitor stimuli and react so as toThey both monitor stimuli and react so as to

maintain homeostasis.maintain homeostasis.

Differences:Differences:

The NS is a rapid, fastThe NS is a rapid, fast--acting system whoseacting system whose

effects do not always persevere.effects do not always persevere.

The ES acts slower (via bloodThe ES acts slower (via blood--borne chemicalborne chemicalsignals and its actions are usually muchsignals and its actions are usually much

longer lasting.longer lasting.

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Organization of theOrganization of the

Nervous SystemNervous System

2 big initial divisions:2 big initial divisions:1.1. Central Nervous SystemCentral Nervous System

The brain + the spinal cordThe brain + the spinal cord

The center of integration and controlThe center of integration and control

2.2. Peripheral Nervous SystemPeripheral Nervous SystemThe nervous system outside of theThe nervous system outside of thebrain and spinal cordbrain and spinal cord

Consists of:Consists of:

31 Spinal nerves31 Spinal nerves

Carry info to and from the spinalCarry info to and from the spinalcordcord

12 Cranial nerves12 Cranial nerves

Carry info to and from the brainCarry info to and from the brain

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Peripheral Nervous SystemPeripheral Nervous System

Responsible for communication btwn the CNSResponsible for communication btwn the CNSand the rest of the body.and the rest of the body.

Can be divided into:Can be divided into: Sensory DivisionSensory Division

Afferent divisionAfferent division Conducts impulses from receptors to the CNSConducts impulses from receptors to the CNS

Informs the CNS of the state of the body interior and exteriorInforms the CNS of the state of the body interior and exterior

Sensory nerve fibers can beSensory nerve fibers can be somaticsomatic (from skin, skeletal(from skin, skeletalmuscles or joints) ormuscles or joints) orvisceralvisceral (from organs w/i the ventral body(from organs w/i the ventral bodycavity)cavity)

Motor DivisionMotor DivisionEfferent divisionEfferent division

Conducts impulses from CNS to effectors (muscles/glands)Conducts impulses from CNS to effectors (muscles/glands)

Motor nerve fibersMotor nerve fibers

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Motor Efferent DivisionMotor Efferent Division

Can be divided further:Can be divided further:

Somatic nervous systemSomatic nervous system

VOLUNTARY (generally)VOLUNTARY (generally)

Somatic nerve fibers that conduct impulses fromSomatic nerve fibers that conduct impulses from

the CNS to skeletal musclesthe CNS to skeletal muscles

Autonomic nervous systemAutonomic nervous system

INVOLUNTARY (generally)INVOLUNTARY (generally)Conducts impulses from the CNS to smoothConducts impulses from the CNS to smooth

muscle, cardiac muscle, and glands.muscle, cardiac muscle, and glands.

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Autonomic Nervous SystemAutonomic Nervous System

Can be divided into:Can be divided into: Sympathetic NervousSympathetic Nervous

SystemSystem

Fight or FlightFight or Flight

ParasympatheticParasympathetic

Nervous SystemNervous System

Rest and DigestRest and Digest

These 2 systems are antagonistic.These 2 systems are antagonistic.

Typically, we balance these 2 to keep ourselves in aTypically, we balance these 2 to keep ourselves in a

state of dynamic balance.state of dynamic balance.

Well go further into the difference btwn these 2 inWell go further into the difference btwn these 2 in

detail later!detail later!

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Peripheral

Nervous

SystemThe PNS is broken down

into a sensory and a motor

division.

motor division contains thesomatic nervous system

and the autonomic

nervous system.

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Autonomic Nervous System

2 divisions:

Sympathetic

Fight or flight

E division Exercise, excitement,

emergency, and

embarrassment

Parasympathetic

Rest and digestD division

Digestion, defecation,

and diuresis

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Somatic vs. Autonomic

Voluntary

Skeletal muscle

Single efferent neuron

Axon terminals releaseacetylcholine

Always excitatory

Controlled by the

cerebrum

Involuntary

Smooth, cardiac muscle;glands

Multiple efferent neuronsAxon terminals releaseacetylcholine ornorepinephrine

Can be excitatory or

inhibitoryControlled by thehomeostatic centers in thebrain pons,hypothalamus, medulla

oblongata

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CommunicationCommunication

Thus, neurons need to be able toThus, neurons need to be able to

conduct information in 2 ways:conduct information in 2 ways:

1.1. From one end of a neuron to the other end.From one end of a neuron to the other end.

2.2. Across the minute space separating oneAcross the minute space separating one

neuron from another.neuron from another.

The 1The 1stst is accomplished electrically via APs.is accomplished electrically via APs.

The 2The 2ndnd is accomplished chemically viais accomplished chemically vianeurotransmitters.neurotransmitters.

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Action PotentialsAction Potentials

If VIf VMM

reaches threshold, Nareaches threshold, Na++ channels open and Nachannels open and Na++ influxinfluxensues, depolarizing the cell and causing the Vensues, depolarizing the cell and causing the VMM totoincrease. This is the rising phase of an AP.increase. This is the rising phase of an AP.

Eventually, the NaEventually, the Na++ channel will have inactivated and thechannel will have inactivated and theKK++ channels will be open. Now, Kchannels will be open. Now, K++ effluxes andeffluxes and

repolarization occurs. This is the falling phase.repolarization occurs. This is the falling phase. KK++ channels are slow to open and slow to close. This causes thechannels are slow to open and slow to close. This causes the

VVMM to take a brief dip below resting Vto take a brief dip below resting VMM. This dip is the. This dip is the undershootundershootand is an example ofand is an example ofhyperpolarizationhyperpolarization..

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Thank YouThank You

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NMJ is blockedNMJ is blocked

Characterized by:Characterized by:

WeaknessWeaknessEasy fatigabilityEasy fatigability

Facial, oculomotor, laryngeal, pharyngealFacial, oculomotor, laryngeal, pharyngeal

and respiratory muscles are affected.and respiratory muscles are affected.

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Drugs usedDrugs used

AntiAnti--cholinesterasescholinesterases

Neostigmine and tensilon (preparation ofNeostigmine and tensilon (preparation of

edrophonium)edrophonium)