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The Muscular SystemThe Muscular System

Chapter 8Chapter 8

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Three Kinds of Muscle TissueThree Kinds of Muscle Tissue

1.1. Smooth > Involuntary > Organ & Smooth > Involuntary > Organ & VesselsVessels

2.2. Cardiac > Involuntary > HeartCardiac > Involuntary > Heart

3.3. Skeletal > Voluntary > Stimulated Skeletal > Voluntary > Stimulated to Contract by the Nervous Systemto Contract by the Nervous System

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Skeletal MuscleSkeletal Muscle

Attaches to bones & produces Attaches to bones & produces movement at jointsmovement at joints

Make up the largest amount of muscle Make up the largest amount of muscle tissue in the bodytissue in the body

Makes up about 40% of total body Makes up about 40% of total body weightweight

The body is composed of almost 700 The body is composed of almost 700 individual skeletal musclesindividual skeletal muscles

Usually act in groups to execute a Usually act in groups to execute a body movementbody movement

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Three Primary Functions of Three Primary Functions of Skeletal MuscleSkeletal Muscle

1.1. MovementMovement - of the skeleton - of the skeleton

2.2. Maintenance of postureMaintenance of posture – a – a steady partial contraction of muscle steady partial contraction of muscle called called MUSCLE TONEMUSCLE TONE keeps the keeps the body in positionbody in position

3.3. Generate heatGenerate heat – a natural by- – a natural by-product of muscle cell metabolismproduct of muscle cell metabolism

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Muscle ContractionMuscle Contraction Two proteins Two proteins

called ACTIN & called ACTIN & MYOSIN are MYOSIN are contained in contained in muscle fibermuscle fiber

They “latch on” They “latch on” to each other, to each other, and with the and with the energy of ATP, energy of ATP, slide together slide together to cause the to cause the muscle fibers to muscle fibers to contractcontract

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Types of Muscle ContractionTypes of Muscle Contraction Muscle ToneMuscle Tone – partially contracted state – partially contracted state

IsotonicIsotonic – muscle tone or tension remains – muscle tone or tension remains the same, but the muscle shortens to the same, but the muscle shortens to produce movement – Ex: lifting weights, produce movement – Ex: lifting weights, walking, runningwalking, running

IsometricIsometric – no change in muscle length, – no change in muscle length, but there is a tremendous increase in but there is a tremendous increase in muscle tension – Ex: pushing against an muscle tension – Ex: pushing against an immovable object or forceimmovable object or force

** Most movements involve a combination of ** Most movements involve a combination of isotonic & isometric contractionsisotonic & isometric contractions

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Attachments of Skeletal MusclesAttachments of Skeletal Muscles

Tendons – attach Tendons – attach muscle to bonemuscle to bone

Origin – is the Origin – is the relatively STABLE part relatively STABLE part of the skeleton where of the skeleton where the muscle is attachedthe muscle is attached

Insertion –is the FREE Insertion –is the FREE MOVING part of the MOVING part of the skeleton where the skeleton where the muscle attaches to muscle attaches to cause movementcause movement

Biceps origin is at the Biceps origin is at the scapulascapula

Biceps insertion is on Biceps insertion is on the radius and allows the radius and allows flexion of the arm at flexion of the arm at the elbowthe elbow

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Prime MoversPrime Movers – – are the muscles are the muscles that perform the that perform the actual movementactual movement

AntagonistsAntagonists – are – are the muscles that the muscles that produce the produce the opposite movement opposite movement of the prime moverof the prime mover

Biceps contract Biceps contract and flex and would and flex and would be the prime be the prime movermover

Triceps relax and Triceps relax and extend and would extend and would be the antagonistbe the antagonist

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Skeletal Muscle GroupsSkeletal Muscle Groups

Different characteristics can be used Different characteristics can be used when naming muscles:when naming muscles:

1.1. Location or PositionLocation or Position – lateral, – lateral, medial, internal, external, etc.medial, internal, external, etc.

2.2. SizeSize – maximus, major, minor, etc. – maximus, major, minor, etc.

3.3. ShapeShape – triangular (deltoid), – triangular (deltoid), trapezoid (trapezius), etc.trapezoid (trapezius), etc.

4.4. ActionAction – flexor, adductor, abductor, – flexor, adductor, abductor, etc.etc.

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Effects of Aging on MusclesEffects of Aging on Muscles

Age 40 begins a gradual loss of muscle Age 40 begins a gradual loss of muscle cells which results in a decrease in cells which results in a decrease in muscle sizemuscle size

Loss of power – especially in the Loss of power – especially in the vertebral column – causes the “bent vertebral column – causes the “bent over” appearance of KYPHOSIS over” appearance of KYPHOSIS (hunchback)(hunchback)

Activity and life-long exercise can delay Activity and life-long exercise can delay the onset of undesirable effects of agingthe onset of undesirable effects of aging

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Muscle DiseasesMuscle Diseases Muscular DystrophyMuscular Dystrophy – is a group of – is a group of

disorders where there is a disorders where there is a deterioration of muscledeterioration of muscle

This disease:This disease:• Progresses at different ratesProgresses at different rates• Occurs more frequently in malesOccurs more frequently in males• Causes weakness & paralysisCauses weakness & paralysis• Causes death due to weakness in Causes death due to weakness in

cardiac muscle or paralysis of cardiac muscle or paralysis of respiratory musclesrespiratory muscles

• Life expectancy between 20 & 40 yearsLife expectancy between 20 & 40 years• Has no known cureHas no known cure

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Myasthenia GravisMyasthenia Gravis – is a chronic – is a chronic disease that causes fatigue with disease that causes fatigue with the slightest exertionthe slightest exertion

Affects adultsAffects adults Begins with the muscles of the Begins with the muscles of the

head and neckhead and neck

MyalgiaMyalgia - chronic muscle pain - chronic muscle pain

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Disorders Associated with StructuresDisorders Associated with Structures

BursitisBursitis – inflammation of the bursa sacs – inflammation of the bursa sacs which include:which include:

• ““Housemaid’s Knee”Housemaid’s Knee” –patella bursa inflames –patella bursa inflames due to pressure on the kneedue to pressure on the knee

• Ischial BursitisIschial Bursitis – common among people who – common among people who sit a lotsit a lot

• ““Student’s Elbow”Student’s Elbow” – point of the elbow – point of the elbow becomes inflamedbecomes inflamed

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BunionsBunions

Enlargements Enlargements commonly commonly found at the found at the base and side of base and side of the big toethe big toe

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TendonitisTendonitis

Inflammation of the Inflammation of the tendons from tendons from overexertionoverexertion

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Carpal TunnelCarpal Tunnel

““repetitive-use” repetitive-use” syndrome that syndrome that affects muscles affects muscles and nerves and nerves supplying the supplying the hands and fingershands and fingers

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Muscular Disorders Due to Spasm or Muscular Disorders Due to Spasm or InjuryInjury

SpasmSpasm – sudden, involuntary – sudden, involuntary muscular contraction which is painfulmuscular contraction which is painful

CrampsCramps – strong, painful contractions – strong, painful contractions StrainsStrains – common injury caused by – common injury caused by

overuse or overstretchingoveruse or overstretching ““Charley Horse”Charley Horse” – soreness and – soreness and

stiffness in a muscle caused by a stiffness in a muscle caused by a strainstrain

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SprainsSprains – are more severe than – are more severe than strains and can involve detachments strains and can involve detachments of muscles from bones, tearing of of muscles from bones, tearing of muscles, damage to ligaments, blood muscles, damage to ligaments, blood vessels or nervesvessels or nerves

AtrophyAtrophy – wasting away of or – wasting away of or decrease in the size of a muscle from decrease in the size of a muscle from lack of uselack of use

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Rigor MortisRigor Mortis

A stage of rigidity of muscles after A stage of rigidity of muscles after death occursdeath occurs

Calcium escapes and causes actin Calcium escapes and causes actin and myosin to slide together and and myosin to slide together and contractcontract

With no ATP being produced, With no ATP being produced, muscles remain contracted and muscles remain contracted and become rigidbecome rigid

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Effects of ExerciseEffects of Exercise

VasodilationVasodilation – is the increase in the – is the increase in the diameter of blood vesselsdiameter of blood vessels

Allows blood to flow more easilyAllows blood to flow more easily More blood is pumped to the heartMore blood is pumped to the heart Increased load on the heart Increased load on the heart

strengthens cardiac muscle and strengthens cardiac muscle and improves circulationimproves circulation