The Muscular System Roselyn Aperocho-Naranjo Pharmacy Instructor USPF-College of Pharmacy

The The Muscular Muscular SystemSystem

Roselyn Aperocho-NaranjoPharmacy InstructorUSPF-College of Pharmacywww.roselynnaranjo.vze.com

Muscle System FunctionsMuscle System Functions

Provides voluntary Provides voluntary movement of bodymovement of body– Enables breathing, Enables breathing,

blinking, and blinking, and smilingsmiling

– Allows you to hop, Allows you to hop, skip, jump, or do skip, jump, or do push-ups push-ups

Maintains postureMaintains posture Produces heatProduces heat

Functions ContinuedFunctions Continued

Causes heart beatCauses heart beat Directs circulation Directs circulation

of blood of blood – RegulatesRegulates

blood blood pressurepressure

– Sends blood to Sends blood to different areas of different areas of the bodythe body

Functions ContinuedFunctions Continued Provides movement of Provides movement of

internal organsinternal organs– Moves food through Moves food through

digestive tractdigestive tract– Enables bladder controlEnables bladder control

Causes involuntary Causes involuntary actionsactions– Reflex actions Reflex actions – Adjusts opening of pupilsAdjusts opening of pupils– Causes hair to stand on Causes hair to stand on

end ( )end ( )

Muscle Tissue Muscle Tissue CharacteristicsCharacteristics

Is made up of Is made up of contractile fiberscontractile fibers

Provides movementProvides movement Controlled by the Controlled by the

nervous systemnervous system– Voluntary- consciously Voluntary- consciously

controlledcontrolled– Involuntary- not under Involuntary- not under

conscious controlconscious control ExamplesExamples

– SkeletalSkeletal– SmoothSmooth– CardiacCardiac

CardiacCardiac

SkeletalSkeletal

SmoothSmooth

Types of Muscle TissueTypes of Muscle Tissue

There are There are three main three main types of types of muscle tissuemuscle tissue– SkeletalSkeletal

(striated)(striated)– CardiacCardiac

(heart)(heart)– SmoothSmooth

(visceral)(visceral)

Comparison of Muscle TypesComparison of Muscle Types

Muscle TypeMuscle Type CardiacCardiac

FunctionFunctionMovement of Movement of

bonebone

Walls of internal Walls of internal organs + in skinorgans + in skinLocationLocation

Attached to Attached to bonebone

HeartHeart

SmoothSmoothSkeletalSkeletal

Striated- light Striated- light and dark bandsand dark bands

Many nucleiMany nuclei

StriatedStriatedOne or two One or two

nucleinuclei

CharacteristicsCharacteristicsNon-striatedNon-striatedOne nucleusOne nucleus

(visceral)(visceral)

Long + slenderLong + slender BranchingBranchingShapeShape Spindle shapeSpindle shape

Control ModeControl Mode

Beating of heartBeating of heart

InvoluntaryInvoluntary InvoluntaryInvoluntary

Movement of Movement of internal organsinternal organs

VoluntaryVoluntary

Location of Location of MusclesMuscles

SkeletalSkeletalMusclesMuscles– Anterior Anterior

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Quadriceps Quadriceps groupgroup

Rectus abdominisRectus abdominis

Quadriceps GroupQuadriceps Group

External ObliquesExternal Obliques

FrontalisFrontalis

MasseterMasseter

Tibialis AnteriorTibialis Anterior

DeltoidDeltoidPectoralis MajorPectoralis Majorbiceps brachiibiceps brachii

BrachioradialisBrachioradialis

LocationLocationof Musclesof Muscles

SkeletalSkeletalMusclesMuscles– PosteriorPosterior

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Hamstring group

TrapeziusTrapezius

Hamstring Hamstring groupgroup

GastrocnemiusGastrocnemius

Latissimus dorsiLatissimus dorsi

Gluteus Gluteus maximusmaximus

Triceps brachiiTriceps brachii

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Muscles You Need to KnowMuscles You Need to Know 1. brachioradialis1. brachioradialis 2. biceps brachii2. biceps brachii 3. deltoid3. deltoid 4. external oblique4. external oblique 5. frontalis5. frontalis 6. gastrocnemius6. gastrocnemius 7. gluteus maximus7. gluteus maximus 8. hamstring group8. hamstring group 9. latissimus dorsi9. latissimus dorsi 10. masseter10. masseter 11. pectoralis major11. pectoralis major 12. quadriceps group12. quadriceps group 13. rectus abdominis13. rectus abdominis 14. tibialis anterior14. tibialis anterior 15. trapezius15. trapezius 16. triceps brachii16. triceps brachii

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Location of MusclesLocation of Muscles

InvoluntaryInvoluntaryMusclesMuscles– DiaphragmDiaphragm– Digestive Digestive

organsorgans– Arrector pili Arrector pili – HeartHeart– Urinary bladderUrinary bladder– Muscles aroundMuscles around

blood vesselsblood vessels

Muscle Tissue AnatomyMuscle Tissue Anatomy

bundle of muscle bundle of muscle fibers – fasciclefibers – fascicle

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MuscleMuscle

FilamentsFilaments

MyofibrilsMyofibrils

Muscle FibersMuscle Fibers

FascicleFascicle

Muscles are made up of bundlesof muscle fibers, called fascicles– Fascicle is a bundle of

muscle fibers A muscle fiber is a

muscle cell….made up of many small myofibrils

– Myofibrils contain filaments

Two types ofprotein filaments

SarcomereSarcomere

MyofibrilMyofibril

Contain two types of Contain two types of protein filamentsprotein filaments– Actin- thinActin- thin

proteinproteinfilamentsfilaments

– Myosin- thickMyosin- thickprotein filamentsprotein filaments

– Z disc- point of Z disc- point of anchor of actinanchor of actin

– Sarcomere- Sarcomere- functional unit of functional unit of a myofibril, a myofibril, region between Z region between Z discs, discs,

Thin FilamentsThin Filaments

ActinActinMoleculeMolecule

Thick FilamentsThick Filaments

Myosin MoleculeMyosin Molecule

Z DiscZ Disc

SarcomereSarcomere

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Muscle TissueMuscle TissueAnatomyAnatomy

What parts do you What parts do you remember?remember?

1. Muscle1. Muscle

2. Fascicle 2. Fascicle (bundle of fibers) (bundle of fibers)

3. Muscle fiber 3. Muscle fiber (muscle cell) (muscle cell)

4. Myofibrils4. Myofibrils33

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Muscle cell Muscle cell MyofibrilsMyofibrils MyosinMyosin SarcomereSarcomere Z DiscZ Disc

ActinActin FascicleFascicle FilamentsFilaments MuscleMuscle

Muscle Tissue Anatomy ContinuedMuscle Tissue Anatomy Continued

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What parts do you remember?....continuedWhat parts do you remember?....continued

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Mechanics of a Muscle Mechanics of a Muscle ContractionContraction

What stimulates a muscle to What stimulates a muscle to contract?contract?– Your nervous systemYour nervous system

What cells are involved?What cells are involved?– Muscle cells and a motor Muscle cells and a motor

neuronneuron– Motor neuron sends Motor neuron sends

impulse to muscle cellsimpulse to muscle cells– One neuron will form One neuron will form

synapses with many synapses with many muscle cellsmuscle cells

What is this called?What is this called?– A motor unitA motor unit– Let’s take a look under Let’s take a look under

the microscope.…the microscope.…A motor unitA motor unit


Where does stimulation occur?Where does stimulation occur?– Neuromuscular junctionNeuromuscular junction

How do motor neurons How do motor neurons communicate with communicate with muscle cells?muscle cells?– Neurotransmitters (typicallyNeurotransmitters (typically

acetylcholine) carryacetylcholine) carryimpulse signal across the gapimpulse signal across the gap

What happens when a What happens when a muscle cell is stimulated?muscle cell is stimulated?– Calcium ions are released into the Calcium ions are released into the

muscle cellmuscle cellMyofibrils are surrounded by

calcium-containing

sarcoplasmic reticulum.

NeurotransmittersNeurotransmitters


What do calcium ions do?What do calcium ions do?– Cause interaction between actin and myosinCause interaction between actin and myosin

How do actin and myosin interact?How do actin and myosin interact?– Actin filaments slide over the myosin Actin filaments slide over the myosin

filaments.filaments. What model explains this?What model explains this?

– Sliding Filament ModelSliding Filament Model


What causes actin to slide What causes actin to slide over myosin?over myosin?– The head of myosin The head of myosin

connects to actin and connects to actin and pivots.pivots.

What is this connection What is this connection called?called?– cross-bridge cross-bridge

The binding of the myosin The binding of the myosin heads throughout the heads throughout the sarcomere occur sarcomere occur asynchronously…asynchronously…– some myosin heads are some myosin heads are

binding while other heads binding while other heads are releasing the actin are releasing the actin filaments. filaments.

– This process must be This process must be performed repeatedly during performed repeatedly during a single muscle contraction a single muscle contraction so that the muscle is able to so that the muscle is able to generate a smooth forcegenerate a smooth force


What provides the energy to swivel the head What provides the energy to swivel the head of myosin? _____of myosin? _____

How exactly does the sliding filament model How exactly does the sliding filament model work?work?– In the sliding filament model of muscle contraction,

the (thin) actin filaments[red] (that are attachedto the Z-line) slide (areactually pulled) inward along the (thick)myosin filaments [blue], and the sarcomere (measuredfrom one Z line to thenext) is shortened.

ATPATP


When each sarcomere becomes shorter When each sarcomere becomes shorter it causes each myofibril to become it causes each myofibril to become shorter.shorter.

When each When each myofibril becomesmyofibril becomesshorter it causes shorter it causes the muscle fibers the muscle fibers to become shorterto become shorter

When each When each muscle fiber muscle fiber shortens the shortens the overall muscle overall muscle contracts.contracts.

SarcomereSarcomere

Control of a Muscle Control of a Muscle ContractionContraction

How long does a muscle cell How long does a muscle cell remain contracted?remain contracted?– Until the release of acetylcholineUntil the release of acetylcholine

stops.stops. How strongly does a muscle fiber contract?How strongly does a muscle fiber contract?

– To it’s fullest extent.To it’s fullest extent.– All-or-none responseAll-or-none response

So what controls the So what controls the strength of a contraction?strength of a contraction?– Number of muscle cells recruitedNumber of muscle cells recruited– To get a stronger contraction, To get a stronger contraction,

more cells are stimulatedmore cells are stimulated– A single cell can’t contract harderA single cell can’t contract harder

A Closer Look at Muscle ContractionA Closer Look at Muscle Contraction

““hot”hot”guyguy

Deltoid Deltoid musclemuscle

MuscleMuscleFiberFiber

MyofibrilMyofibril

sarcomeresarcomere

ActinActin

MyosinMyosin

Macroscopic Structure Macroscopic Structure of Muscle of Muscle

_________- attaches _________- attaches muscle to bonemuscle to bone

_______- attachment _______- attachment of muscle to of muscle to immovable (fixed) immovable (fixed) bone (anchors bone (anchors muscle)muscle)

________- attachment ________- attachment to bone that moves to bone that moves when muscle when muscle contractscontracts

_____- bulging middle _____- bulging middle part of the musclepart of the muscle

Belly ofBelly of BicepsBiceps

TendonTendon

OriginOrigin

InsertionInsertion

BellyBelly

Muscle MovementMuscle Movement Muscles originate on a _____bone in our body, Muscles originate on a _____bone in our body,

cross over a ______, and insert onto a ______ cross over a ______, and insert onto a ______ bone. bone.

It is important to understand that all muscles It is important to understand that all muscles move from the ________ point move from the ________ point going toward the __________ going toward the __________ point. point.

It is because of the It is because of the placement of the muscles placement of the muscles that we can that we can move.move.

jointjointfixedfixed

movingmoving

insertioninsertionoriginationorigination

Muscle MovementMuscle Movement Tendons Tendons

– attach _________ to boneattach _________ to bone– are inelastic are inelastic – don’t stretch when the force don’t stretch when the force

of the muscle acts on them of the muscle acts on them When muscle contracts, When muscle contracts,

it pulls on the _______it pulls on the _______ Individual muscles can Individual muscles can

only ____ in ____ directiononly ____ in ____ direction Muscles work in Muscles work in

opposing ______opposing ______

musclemuscle

bonebone

pullpull oneone

pairspairs

Muscle MovementMuscle Movement ______-______- Muscle that bends the joint when Muscle that bends the joint when

contracted.contracted. ________-________- Muscle that straightens the joint Muscle that straightens the joint

when contracted.when contracted. __________ muscle__________ muscle

is short, firm, tight is short, firm, tight and thicker around.and thicker around.

_______ muscle is _______ muscle is stretched, long, loose stretched, long, loose and thinner around.and thinner around.

FlexorFlexor

ExtensorExtensor

RelaxedRelaxed

ContractedContracted

Muscle MovementMuscle Movement When the When the bicepsbiceps in the arm contracts the in the arm contracts the triceps triceps

________________ causing ________ of the arm. causing ________ of the arm. When the When the tricepstriceps in the arm _________ the in the arm _________ the bicepsbiceps

relaxes causing ____________ of the arm.relaxes causing ____________ of the arm.

relaxesrelaxes

______ of muscles ______ of muscles are needed because are needed because the only active the only active _________ of a _________ of a muscle is to _______, muscle is to _______, to lengthen it must to lengthen it must be _________ by the be _________ by the action of an action of an opposing _______. opposing _______.

bendingbendingcontractscontracts

straighteningstraightening

PairsPairs

movementmovement

contractcontractstretchedstretched

musclemuscle

Muscle MovementMuscle Movement

The muscles, bones, and ligaments work together to control body motion.

I am I am getting getting motion motion sicknessicknes

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Warning: This illusion Warning: This illusion can make you feel very can make you feel very dizzy, especially if you dizzy, especially if you

are prone to motion are prone to motion sicknesssickness

Muscles In ActionMuscles In Action

Click above to get to this multimedia interactive Click above to get to this multimedia interactive HTML document which will help you learn the HTML document which will help you learn the muscle actions of the human body. muscle actions of the human body.

HYPERMUSCLE: MUSCLES IN ACTION

Muscle + Bone InteractionMuscle + Bone Interaction

Let’s review the structures involved in Let’s review the structures involved in movement at a joint. movement at a joint.

LigamentLigament TendonTendon CartilageCartilage Body (Belly)Body (Belly) OriginOrigin InsertionInsertion Contracted Contracted

musclemuscle Relaxed muscleRelaxed muscle FlexorFlexor ExtensorExtensor

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Muscle DisordersMuscle Disorders

A sprain is a wrenching, twisting or A sprain is a wrenching, twisting or stretchingstretching injury to a ligament. injury to a ligament.

Sprains often affect theSprains often affect theankles, knees, or wrists.ankles, knees, or wrists.

SprainSprain

Result in pain, swelling, redness, bruising, and Result in pain, swelling, redness, bruising, and difficulty using injured joint.difficulty using injured joint.

Muscle DisordersMuscle Disorders A strain is an injury to a muscle or tendon, and A strain is an injury to a muscle or tendon, and

is often caused by overuse, force, or stretching.is often caused by overuse, force, or stretching.

Injured area Injured area experiences: experiences: – pain and sorenesspain and soreness– swelling swelling – warmth, bruising, warmth, bruising,

or redness or redness – difficulty using or difficulty using or

moving the moving the injured area in a injured area in a normal mannernormal manner

StrainStrain


There are three degrees of muscle ruptures There are three degrees of muscle ruptures A muscle tear may be partial or complete and caused A muscle tear may be partial or complete and caused

either by a direct blow or by overexertion.either by a direct blow or by overexertion. A first-degree strain involves less than 5 percent of the A first-degree strain involves less than 5 percent of the

muscle. muscle. – mild pain and not much loss of strength or range of motion.mild pain and not much loss of strength or range of motion.– Mild tears referred to as pulled muscles.Mild tears referred to as pulled muscles.

A second-degree tear is a greater rupture that stops A second-degree tear is a greater rupture that stops short of a complete tear.short of a complete tear.– Any contraction of the torn muscle will cause pain. Any contraction of the torn muscle will cause pain. – There may be a defect of the muscle - a bump or an There may be a defect of the muscle - a bump or an

indentation - at the site of the most pain. indentation - at the site of the most pain. – You should be able to partially contract the muscle, but not You should be able to partially contract the muscle, but not

without painwithout pain A third-degree rupture is a complete tear across the A third-degree rupture is a complete tear across the

width of the musclewidth of the muscle– You will be unable to contract the muscle. You will be unable to contract the muscle. – This is what happens when someone suddenly drops while This is what happens when someone suddenly drops while

sprinting. sprinting. – The torn end of the muscle may ball up and form a large The torn end of the muscle may ball up and form a large

lump under the skin, and a great deal of internal bleeding lump under the skin, and a great deal of internal bleeding occurs. occurs.

– Severely torn muscles may require surgery to heal properly.Severely torn muscles may require surgery to heal properly.

Muscle RupturesMuscle Ruptures


Muscle pull- very slight tearMuscle pull- very slight tear Chronic tear- gradual onset of painChronic tear- gradual onset of pain Acute tear- sudden dramatic pain Acute tear- sudden dramatic pain

Muscle PullMuscle Pull Muscle TearMuscle Tear

Muscle Muscle TearsTears


Shin splints is pain Shin splints is pain resulting from damage to resulting from damage to the muscles along the shin.the muscles along the shin.

Pain is felt in different areas, depending on which muscles are affected.

Shin splintsShin splints

Shin splints represent an "overuse injury" and occur most commonly in runners.


R.I.C.E.R.I.C.E. Rest:Rest: Stop all activities which Stop all activities which

cause pain. cause pain. Ice:Ice: Helps reduce swelling. Helps reduce swelling.

Never ice more than 10-15 min. Never ice more than 10-15 min. at a time. Protect the skin. at a time. Protect the skin.

Compression:Compression: Wrap the strained Wrap the strained area to reduce swelling. area to reduce swelling.

Elevation:Elevation: Keep the strained Keep the strained area as close to the level of the area as close to the level of the heart as is conveniently possible heart as is conveniently possible to keep blood from pooling in the to keep blood from pooling in the injured area.injured area.

Treatment for Muscle InjuriesTreatment for Muscle Injuries


Muscle spasm- when A muscle (or even a Muscle spasm- when A muscle (or even a few fibers of a muscle) involuntarily few fibers of a muscle) involuntarily contract contract

Muscle cramp- involuntarily + forcibly Muscle cramp- involuntarily + forcibly contracted muscle that does not relaxcontracted muscle that does not relax – A forceful + sustained spasmA forceful + sustained spasm– Nick named charley horseNick named charley horse

CrampsCrampsSpasmsSpasms

– Can last anywhere from a few Can last anywhere from a few seconds to a quarter of an hour seconds to a quarter of an hour

– Caused by strain or injuryCaused by strain or injury

– Muscle feels tied up in knotsMuscle feels tied up in knots


Tetanus is a preventable disease through Tetanus is a preventable disease through vaccination vaccination

Caused by bacteria that enters the body Caused by bacteria that enters the body through the skin through the skin

Found in soil, dust and manure Found in soil, dust and manure Toxin bacteria produces interferes with nerve Toxin bacteria produces interferes with nerve

transmission to your muscles and causes transmission to your muscles and causes them to seize up in painful spasms.them to seize up in painful spasms.

Tetanus typically starts in the jaw and muscles Tetanus typically starts in the jaw and muscles of the face, quickly spreading to the arms and legs. of the face, quickly spreading to the arms and legs.

– ““Lockjaw”Lockjaw”– Difficulty swallowing Difficulty swallowing – Intestines often seize upIntestines often seize up– Bladder fails to emptyBladder fails to empty– Asphyxiation Asphyxiation – Cardiac arrest Cardiac arrest

TetanusTetanus


Produced naturally by the body to support such functions Produced naturally by the body to support such functions as fighting stress and promoting growth and developmentas fighting stress and promoting growth and development

Referred to as roids, juice, hype, weight trainers, gym Referred to as roids, juice, hype, weight trainers, gym candy, arnolds, stackers, or pumperscandy, arnolds, stackers, or pumpers

People use steroid pills, gels, creams, or injections to People use steroid pills, gels, creams, or injections to improve their sports performance or the way they look. improve their sports performance or the way they look.

Anabolic steroids cause many different types of problemsAnabolic steroids cause many different types of problems types of problems types of problems

– premature balding or hair loss premature balding or hair loss – dizziness dizziness – mood swingsmood swings– problems sleeping problems sleeping – nausea and vomiting nausea and vomiting – high blood pressurehigh blood pressure– aching joints aching joints – urinary problems urinary problems – shortening of final adult height shortening of final adult height – increased risk of heart disease,increased risk of heart disease,

stroke, and some cancers stroke, and some cancers

Anabolic SteroidsAnabolic Steroids


Cerebral palsy is a group of disorders that affect a Cerebral palsy is a group of disorders that affect a person's ability to move and to maintain balance andperson's ability to move and to maintain balance and posture. posture.

The disorders appear in theThe disorders appear in thefirst few years of life, and first few years of life, and usually don’t get worse over time. usually don’t get worse over time.

People with cerebral palsy People with cerebral palsy may have difficulty walking. They may may have difficulty walking. They may also have trouble with tasks such as also have trouble with tasks such as writing or using scissors. writing or using scissors.

Some people with cerebral palsy have Some people with cerebral palsy have other medical conditions, including other medical conditions, including seizure disorders or mental impairment. seizure disorders or mental impairment.

Cerebral palsy happens when the areas Cerebral palsy happens when the areas of the brain that control movement and of the brain that control movement and posture do not develop correctly or get posture do not develop correctly or get damaged.damaged.

Cerebral PalseyCerebral Palsey


Muscular DystrophyMuscular Dystrophy- most well known of - most well known of hereditary diseaseshereditary diseases

A genetic condition that describes over 20 A genetic condition that describes over 20 genetic and hereditary muscle diseases.genetic and hereditary muscle diseases.

Characterized by progressive skeletal muscle Characterized by progressive skeletal muscle weakness, defects in muscle proteins, and weakness, defects in muscle proteins, and the death of muscle cells and tissue.the death of muscle cells and tissue.

In some cases, cardiac and smooth muscles In some cases, cardiac and smooth muscles are affected. are affected.

– Progressive Muscular Wasting Progressive Muscular Wasting (weakness) (weakness)

– Poor Balance and FPoor Balance and Frequent Falls requent Falls – Walking Difficulty + Waddling Gait Walking Difficulty + Waddling Gait – Limited Range of Movement Limited Range of Movement – Scoliosis (curvature of the spine) Scoliosis (curvature of the spine) – Inability to Walk Inability to Walk – Muscle Atrophy and Drooping EyelidsMuscle Atrophy and Drooping Eyelids

Muscular DystrophyMuscular Dystrophy

Principal symptoms: Principal symptoms:


The characteristic symptom of myasthenia gravis is fatigability, The characteristic symptom of myasthenia gravis is fatigability, which means that a muscle that is used repeatedly starts to which means that a muscle that is used repeatedly starts to become weak. become weak.

The symptoms usually start in the face and spread to the other The symptoms usually start in the face and spread to the other parts of the body as the disease progresses. parts of the body as the disease progresses.

Certain muscles such as those that control eye and eyelid Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are movement, facial expression, chewing, talking, and swallowing are often involvedoften involved

The muscles that control breathing and neck and limb movements The muscles that control breathing and neck and limb movements may also be affected. may also be affected.

Patients initially complain of drooping eye lids that get worst as Patients initially complain of drooping eye lids that get worst as the day goes on; they develop double vision, difficulty talking, and the day goes on; they develop double vision, difficulty talking, and difficulty chewing. difficulty chewing.

Muscle weakness increases during periods of activity and improves Muscle weakness increases during periods of activity and improves after periods of rest. after periods of rest.

Myasthenia gravis-Myasthenia gravis- chronic autoimmune chronic autoimmune neuromuscular disease characterized by neuromuscular disease characterized by varying degrees of weakness of the skeletal varying degrees of weakness of the skeletal musclesmuscles

Caused by a defect in the transmission of Caused by a defect in the transmission of nerve impulses at the neuromuscular junctionnerve impulses at the neuromuscular junction

Antibodies (produced by the body's own Antibodies (produced by the body's own immune system) block, alter, or destroy the immune system) block, alter, or destroy the receptors for acetylcholine at the receptors for acetylcholine at the neuromuscular junction which prevents the neuromuscular junction which prevents the muscle contraction from occurring. muscle contraction from occurring.

Myasthenia GravisMyasthenia Gravis


PoliomyelitisPoliomyelitis, often called , often called poliopolio is an acute is an acuteviral infectious disease which is spread fromviral infectious disease which is spread fromperson-to-person via the fecal-oral route. person-to-person via the fecal-oral route.

The majority of polio infections are asymptomatic. The majority of polio infections are asymptomatic. In about 1% of cases the virus enters the (CNS) via In about 1% of cases the virus enters the (CNS) via

the blood stream. the blood stream. Within the CNS, poliovirus infects and Within the CNS, poliovirus infects and

destroys motor destroys motor neurons. neurons.

PolioPolio

Old PolioAsymmetric atrophy & weaknessAtrophic right leg (arrow) in patient with paralytic polio 70 years in past

The destruction of The destruction of motor neurons motor neurons causes muscle causes muscle weakness and weakness and flaccid paralysisflaccid paralysis

Vaccination created Vaccination created by Jonas Salk in by Jonas Salk in 1955 has 1955 has eliminated eliminated the diseasethe disease

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The Muscular System Roselyn Aperocho-Naranjo Pharmacy Instructor USPF-College of Pharmacy