MUSCULAR MUSCULAR SYSTEMSYSTEM

I. OverviewI. OverviewA.Muscles – 40-50% of body massB.Functions

1. skeletal movement2. control of organ and vessel size3. maintain posture and position4. support soft tissue5. guard entrances and exits6. maintain body temperature

(85%)

1.Skeletal – Striated– Voluntary

C. 3 Kinds of Muscle Tissue

AKA: Somatic Tissue

C. 3 Kinds of Muscle Tissue2. Cardiac

– Heart muscle– Branched cells– Multinucleiated– Thick striations

• Intercalated discs• Increase speed of

impulses

– Involuntary – AKA Visceral

Tissue

3.Smooth – Spindle shaped– Nonstriated – Involuntary – Found around hollow

organs such as arteries, esophagus, stomach

C. 3 Kinds of Muscle Tissue

1.1.ContractilityContractilityAbility to shorten and exert

tension2.2.Excitability Excitability

Ability to respond3.3.ExtensibilityExtensibility

Ability to contract after being stretched

4.4.ElasticityElasticity Ability to regain initial

length after contraction

D. Muscle CharacteristicsD. Muscle Characteristics

I. OverviewI. Overview

1.1.Muscle tissue Muscle tissue 2.2.Connective tissuesConnective tissues3.3.Nervous tissueNervous tissue4.4.BloodBlood

E. Each muscle is an E. Each muscle is an organ comprised oforgan comprised of

II. Anatomy of Skeletal II. Anatomy of Skeletal MuscleMuscle

A.Connective Tissue1.1. Superficial Superficial

FasciaFascia Surround

and separate each muscle

A.A. Connective Tissue2. Deep2. Deep

a.a. EpimysiumEpimysium - whole muscle

b.b. PerimysiumPerimysium - bundles of fibers (fascicles)

c.c. EndomysiumEndomysium - single muscle

fiber

3. 3. TendonsTendonsa. Formed from the union

of all three deep fascia

b. Connect muscle to bone

A.A. Connective Tissue

4. Aponeurosis 4. Aponeurosis – flat sheet

A.A. Connective Tissue

1.1.Each muscle Each muscle fiber fiber a.a.is a single, long, cylindrical is a single, long, cylindrical

muscle cell.muscle cell. – SarcolemmaSarcolemma (cell (cell

membrane) membrane) – SarcoplasmSarcoplasm (cytoplasm) (cytoplasm)

• Many mitochondria Many mitochondria • NucleiNuclei• Sarcoplasmic reticulumSarcoplasmic reticulum

B. Muscle FibersB. Muscle Fibers

B. Muscle FibersB. Muscle Fibers1. Each muscle 1. Each muscle fiberfiber

b. is wrapped in endomysium

1. Each muscle 1. Each muscle fiberfiberc. is a bundle of myofibrils myofibrils

which is made of a budle of myofilaments

2. FasciclesFascicles: a. a bundle

of muscle

fibersb. wrapped

in

perimysium

B. Muscle FibersB. Muscle Fibers

3. Myofibrils 3. Myofibrils a.a. made of made of thinthin and and thick thick

filamentsfilaments

B. Muscle FibersB. Muscle Fibers

3. Myofibrils 3. Myofibrils b.b. Thick filaments made Thick filaments made

up of up of the protein the protein myosinmyosin..

c. Thin filaments are c. Thin filaments are made up made up of the protein of the protein actinactin..

B. Muscle FibersB. Muscle Fibers

Thick filamentsThick filaments

Thin filamentsThin filaments

Tropomyosin and troponin are regulatory proteins

Actin and myosin are contractile proteins.

3. Myofibril3. Myofibril d.d. Together, the thick Together, the thick

and and thin filaments make thin filaments make up the up the striationsstriations

B. Muscle FibersB. Muscle Fibers

B. Muscle FibersB. Muscle Fibers4. Sarcomeres4. Sarcomeres

a. Contractile unit of a muscle

b. Consists of overlapping thick and thin filaments

SarcomereSarcomere

4. Sarcomere4. Sarcomerec. Muscle contractionc. Muscle contraction

results from thick and thin filaments sliding past one another.

B. Muscle FibersB. Muscle Fibers

1. Where the neuron and muscle fiber meet

C. Neuromuscular JunctionC. Neuromuscular Junction

2.The neuron and muscle fibers it controls make up a motor unitmotor unit (2-2000 fibers/unit)

MOTOR UNITMOTOR UNIT

3. When stimulated, all of the muscle fibers of a motor unit

C. Neuromuscular JunctionC. Neuromuscular Junction

contract all at once.

4. Anatomy

Axon terminalAxon terminal – nerve end

C. Neuromuscular JunctionC. Neuromuscular Junction

• Produces a neurotransmitter - acetycholineacetycholine (Ach)

4. Anatomy Motor end plate –site on musclewith

C. Neuromuscular JunctionC. Neuromuscular Junction

acetycholine receptors Synaptic cleftSynaptic cleft - space between the nerve & motor end plate

Motor end plate

III. Skeletal Muscle III. Skeletal Muscle ContractionContractionA. Initiation events

1.1. nerve nerve impulse impulse

2.2. ACh ACh released released

3.3. Ach binds Ach binds to receptor to receptor on muscleon muscle

4.4. Enzyme Enzyme (Acetylcholi(Acetylcholine esterase ne esterase removes removes AChACh

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

B. Action Potential1.1. ACh causes ACh causes to Nato Na++ to to

diffuse into celldiffuse into cell2.2. If threshold is reached, If threshold is reached,

action potential occursaction potential occurs- impulse travels along - impulse travels along membrane resulting in membrane resulting in contractioncontraction

III. Skeletal Muscle III. Skeletal Muscle ContractionContractionC. Sliding Filament TheoryC. Sliding Filament Theory

1.1.Action potential causes CaAction potential causes Ca++++ release from S.Rrelease from S.R

2.2.CaCa++++ binds to thin filament binds to thin filament 3.3.Thin filament rotates exposing Thin filament rotates exposing

binding site for myosin binding site for myosin 4.4.Myosin binds actin Myosin binds actin

» uses ATP to "rachet" once uses ATP to "rachet" once » releases, "and binds to next actinreleases, "and binds to next actin

Calcium is the "switch" that turns muscle "on and off" (contracting and relaxing).

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

D. How Neurotoxins Work D. How Neurotoxins Work 1.1.cobra toxin and curarecobra toxin and curare

– block Ach receptorsblock Ach receptors– cause flaccid paralysis, potentially fatal cause flaccid paralysis, potentially fatal

respiratory arrestrespiratory arrest

2.2.nerve gas and insecticidesnerve gas and insecticides• inhibit AchEinhibit AchE• cause potentially fatal paralytic convulsionscause potentially fatal paralytic convulsions

How a Nerve Gas Works

Normal Nerve Gas

Effect of Atropine on the Transmission of Acetylcholine in the

presence of a nerve agent

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

D. How Neurotoxins WorkD. How Neurotoxins Work3.3.Botulism toxin and curareBotulism toxin and curare

– block Ach releaseblock Ach release– cause flaccid paralysis, potentially fatal cause flaccid paralysis, potentially fatal

respiratory arrestrespiratory arrest

4.4.Tetanus toxinTetanus toxin• cause excessive Ach release from motor neuronscause excessive Ach release from motor neurons• causes potentially fatal paralytic convulsions causes potentially fatal paralytic convulsions

(“lock jaw”)(“lock jaw”)

III. Skeletal Muscle III. Skeletal Muscle ContractionContraction

E. Rigor MortisE. Rigor Mortis• Ca++ pumps run out of ATP Ca++ pumps run out of ATP • Ca++ cannot be removedCa++ cannot be removed• continuous contraction continuous contraction • eventually tissues break down eventually tissues break down

IV. Energy Metabolism in IV. Energy Metabolism in Sk.Ms.Sk.Ms.

1.1.Most efficient use of glucoseMost efficient use of glucoseSources of glucose include blood Sources of glucose include blood glucose and stored glycogenglucose and stored glycogen

2.2.36ATP/glucose36ATP/glucose3.3.requires oxygenrequires oxygen4.4.occurs in mitochondriaoccurs in mitochondria

– Muscle cells have more Muscle cells have more mitochondria than any other cellmitochondria than any other cell

– Require a steady supply of ORequire a steady supply of O22

A. Aerobic RespirationA. Aerobic Respiration

B. B. Creatine-phosphagen Creatine-phosphagen systemsystem

1.1.During rest, muscles store During rest, muscles store energy as creatine energy as creatine phosphokinase (CPK or CK)phosphokinase (CPK or CK)

2.2.During intense exercise, During intense exercise, ATP is depleted first, then ATP is depleted first, then CK is used to convert ADP CK is used to convert ADP back to ATP back to ATP

C. C. Lactic Acid PathwayLactic Acid Pathway

1.1.Anaerobic use of glucose Anaerobic use of glucose 2.2.2 ATP/ glucose2 ATP/ glucose3.3.Lactic acid produced as Lactic acid produced as

waste product – Oxygen waste product – Oxygen DebtDebt– Is toxic to tissueIs toxic to tissue– Can be recycled in liverCan be recycled in liver

V. Muscle TwitchV. Muscle Twitch--cycle of contraction and cycle of contraction and

relaxation relaxation

V. Muscle TwitchV. Muscle Twitch--cycle of contraction and cycle of contraction and

relaxation relaxationA. A. Reasons for varying degrees Reasons for varying degrees

1. The number of muscle fibers 1. The number of muscle fibers innervated by a single neuron innervated by a single neuron varies varies

2. Some motor units have lower 2. Some motor units have lower thresholds than othersthresholds than others

3. Muscle fibers differ 3. Muscle fibers differ functionally: functionally: fast twitch – fast twitch – slow twitch fibersslow twitch fibers

V. Muscle TwitchV. Muscle Twitch

B. B. Fast vs Slow Twitch Fibers Fast vs Slow Twitch Fibers 1. Differ in 1. Differ in

– How they make ATPHow they make ATP

– Speed of ATP break downSpeed of ATP break down

– Mitochondria contentMitochondria content

– How fast they fatigueHow fast they fatigue

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers

2. 2. Slow Twitch FibersSlow Twitch Fibers – Smallest fibers Smallest fibers – Fatigue resistantFatigue resistant– Aerobic ATP productionAerobic ATP production– Many mitochondriaMany mitochondria– Slow contractionsSlow contractions– Example: uroanal musclesExample: uroanal muscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers

2. Oxidative 2. Oxidative Fast Twitch Fast Twitch FibersFibers – Fatigue resistantFatigue resistant– Aerobic ATP productionAerobic ATP production– Many mitochondriaMany mitochondria– Fast contractionsFast contractions– Example: arm musclesExample: arm muscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers

3. Glycolytic 3. Glycolytic Fast Twitch FibersFast Twitch Fibers – Largest fibersLargest fibers– Fatigue easilyFatigue easily– Anaerobic ATP productionAnaerobic ATP production– Few mitochondriaFew mitochondria– Strong fast contractionsStrong fast contractions– Example: sprinter’s leg Example: sprinter’s leg

musclesmuscles

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers4. Muscles have combination of all three 4. Muscles have combination of all three

fibersfibers – The number of each type varies from

individual to individual Endurance runningEndurance running - slow and fast - slow and fast oxidative fibersoxidative fibers SprintsSprints - fast oxidative fibers and some - fast oxidative fibers and some fast glycolytic fibersfast glycolytic fibers PowerliftingPowerlifting - fast glycolytic fibers & - fast glycolytic fibers & some some fast oxidativefast oxidative Old ageOld age - increase in slow oxidative - increase in slow oxidative fibersfibers

B. B. Fast vs Slow Twitch Fast vs Slow Twitch FibersFibers

4. Muscles have 4. Muscles have combination of all three combination of all three fibersfibers

– Training/conditioning can change the predominant fiber type in muscles

Anabolic steroidsAnabolic steroids– similar to testosterone similar to testosterone – large doses required for good effect large doses required for good effect – Side effects: Side effects: – overall - kidney and heart damage, overall - kidney and heart damage,

aggressivenessaggressiveness– females - sterility, facial hair, breast & females - sterility, facial hair, breast &

uterine atrophy uterine atrophy – males - baldness, atrophy of testismales - baldness, atrophy of testis

Sports injuries - RICE Sports injuries - RICE

therapytherapy – Rest Rest

– Ice Ice

– Compression Compression

– Elevation Elevation

V. Skeletal MuscleV. Skeletal Muscle

A. A. Muslce Attachments Muslce Attachments 1.1.Origin - tendons attach Origin - tendons attach

muscle to a stationary bone muscle to a stationary bone

2.2.Insertion - muscle attaches Insertion - muscle attaches to moving bone (usually to moving bone (usually distal) distal)

V. Skeletal MuscleV. Skeletal Muscle

B. B. Lever Systems Lever Systems 1.1.leverlever - rod that moves at the - rod that moves at the

fulcrum (fixed point) fulcrum (fixed point)

2.2.fulcrumfulcrum typically the joint typically the joint moving moving

3.3.ResistanceResistance - gravity pulling - gravity pulling on body on body

4.4.EffortEffort - muscle contraction - muscle contraction

V. Skeletal MuscleV. Skeletal Muscle

B. B. Lever Lever Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – First classFirst class

levers - E F levers - E F RR

V. Skeletal MuscleV. Skeletal Muscle

B. B. Lever Lever Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – 2nd class2nd class

levers – F R levers – F R EE

V. Skeletal MuscleV. Skeletal Muscle

B. B. Lever Lever Systems Systems 4. Movement 4. Movement

occurs when occurs when E > R E > R – 3rd class3rd class

levers – F E levers – F E RRmost commonmost common

V. Skeletal MuscleV. Skeletal Muscle

C. C. Muscle Groups Muscle Groups 1.1.Many muscles are Many muscles are

required for any given required for any given movement movement

– 1 muscle moves arm up 1 muscle moves arm up

– another muscle another muscle moves arm moves arm down down

C. C. Muscle Groups Muscle Groups 2. Muscles work 2. Muscles work

togethertogether– AgonistAgonist

> Prime mover> Prime mover

> muscle that causes a > muscle that causes a movementmovement

– AntagonistAntagonist

> opposes the muscle > opposes the muscle that that stretchesstretches

Biceps – Agonist (prime mover)

Triceps -- Antagonist

Uncurl arm -- roles are reversed

Ex. Arm flexion

C. C. Muscle Groups Muscle Groups 2. Muscles work 2. Muscles work

togethertogether– Synergist Synergist

> Assists the prime > Assists the prime movermover

– FixatorFixator

> auxiliary muscles > auxiliary muscles that that steady a steady a movement movement

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