The Muscular SystemThe Muscular System

Functions of Muscle Functions of Muscle TissueTissue

• Movement FacilitationMovement Facilitation• ThermogenesisThermogenesis• Postural SupportPostural Support• Regulation of Organ VolumeRegulation of Organ Volume• Protects Internal Organs Protects Internal Organs • Pumps Blood Pumps Blood (HEART)(HEART)

Characteristics of Characteristics of Muscle TissueMuscle Tissue

• Elasticity – able to return to original Elasticity – able to return to original shape.shape.

• Excitability (Irritability) – able to Excitability (Irritability) – able to respond to a stimulus.respond to a stimulus.

• Extensibility (Flexibility) – able to Extensibility (Flexibility) – able to lengthen.lengthen.

• Contractility – able to shorten.Contractility – able to shorten.

Three Muscle Tissue Three Muscle Tissue TypesTypes

• Skeletal MuscleSkeletal Muscle• Smooth MuscleSmooth Muscle• Cardiac MuscleCardiac Muscle

Skeletal MuscleSkeletal Muscle

• Function: movement, Function: movement, thermogenesis, posture, protection thermogenesis, posture, protection of internal organsof internal organs

• Location: attached to bonesLocation: attached to bones• Appearance: striatedAppearance: striated• Voluntary control (conscious Voluntary control (conscious

control)control)• MultinucleatedMultinucleated

Smooth (Visceral) Smooth (Visceral) MuscleMuscle

• Located in walls of hollow internal Located in walls of hollow internal surfaces such as:surfaces such as:– blood vesselsblood vessels - stomach- stomach– urinary bladderurinary bladder- intestines- intestines

• Non-striated in appearanceNon-striated in appearance• Involuntary (typically)Involuntary (typically)

PeristalsisPeristalsis• Can be stretched to great lengthsCan be stretched to great lengths• Allows for tremendous size variabilityAllows for tremendous size variability

Cardiac MuscleCardiac Muscle• Forms the bulk of heart wall (Myocardium)Forms the bulk of heart wall (Myocardium)• StriatedStriated• Involuntary (typically)Involuntary (typically)• Fibers are quadrangular and branchingFibers are quadrangular and branching• Cardiac fibers typically have a centrally Cardiac fibers typically have a centrally

located nucleuslocated nucleus• Sarcolemmas connected by intercalated Sarcolemmas connected by intercalated

discsdiscs– Strengthens cardiac muscle tissueStrengthens cardiac muscle tissue– Propagates an action potential from cell to cell Propagates an action potential from cell to cell

through specialized structures on the through specialized structures on the intercalated discs called gap junctionsintercalated discs called gap junctions

What causes a muscle What causes a muscle to contract?to contract?

•

Actin and Myosin called Actin and Myosin called Myofilaments Myofilaments – Myosin - thick myofilamentsMyosin - thick myofilaments– Actin - thin myofilamentsActin - thin myofilaments

•

Muscle Contraction Muscle Contraction AnatomyAnatomy

Actin- Thin FilamentsActin- Thin Filaments Myosin- Thick FilamentsMyosin- Thick Filaments

Z LineZ Line

SarcomereSarcomere

Muscle Contraction Muscle Contraction EventsEvents

Muscle ContractioMuscle ContractioYou Tube Video called “Action Potential” found at http://www.youtube.com/watch?v=70DyJwwFnkU You Tube Video called “Action Potential” found at http://www.youtube.com/watch?v=70DyJwwFnkU

Muscle Action PotentialMuscle Action Potential

An electrical impulse that An electrical impulse that originates at the motor end originates at the motor end plate, travels along the plate, travels along the length of the sarcolemma, length of the sarcolemma, down a transverse tubule, down a transverse tubule, and causes the muscle to and causes the muscle to contract.contract.

Sliding Filament Theory Sliding Filament Theory of Muscular Contractionof Muscular Contraction• Due to an action potential, the Due to an action potential, the

actin and myosin myofilaments actin and myosin myofilaments slide past one another shortening slide past one another shortening the sarcomerethe sarcomere

• No change in length of No change in length of myofilamentsmyofilaments

• Z line shortens and muscle Z line shortens and muscle contractscontracts

Muscle Response to Muscle Response to Nervous StimuliNervous Stimuli

• All or None PrincipleAll or None Principle– Once a threshold stimulus is applied Once a threshold stimulus is applied

to a motor unit the muscle fibers to a motor unit the muscle fibers innervated by that motor unit will innervated by that motor unit will contract to their fullest potentialcontract to their fullest potential

• Threshold Stimulus - the weakest Threshold Stimulus - the weakest stimulus from a neuron that will stimulus from a neuron that will initiate a muscular contractioninitiate a muscular contraction

Graph Muscle Graph Muscle ControactionControaction

DepolarizatioDepolarizationn

Muscle Origin and Muscle Origin and InsertionInsertion

• OriginOrigin– Body segment with most massBody segment with most mass– Usually more proximally locatedUsually more proximally located– Usually larger surface area of attachmentUsually larger surface area of attachment

• InsertionInsertion– Body segment with least massBody segment with least mass– Usually more distally locatedUsually more distally located– Usually smaller surface area of attachmentUsually smaller surface area of attachment

• Gaster (Belly)Gaster (Belly)– Fleshy portion of the muscle between the Fleshy portion of the muscle between the

tendons of the origin and insertiontendons of the origin and insertion

Roles of Skeletal Roles of Skeletal MusclesMuscles

• Agonist (Prime Mover)Agonist (Prime Mover)– Muscle responsible for the majority of Muscle responsible for the majority of

forceforce• AntagonistAntagonist

– Performs the opposite movement Performs the opposite movement • SynergistSynergist

– Muscle that assists the agonistMuscle that assists the agonist• provides additional forceprovides additional force• redirects the force of the agonistredirects the force of the agonist

• Fixator (Stabilizer)Fixator (Stabilizer)– Stabilizes a body segment so the prime Stabilizes a body segment so the prime

mover can act more effectivelymover can act more effectively

Selected Superficial Selected Superficial Skeletal Muscles Skeletal Muscles (Anterior View)(Anterior View)

• Pectoralis majorPectoralis major• DeltoidDeltoid• Biceps brachiiBiceps brachii• SternocleidomastoidSternocleidomastoid• DiaphragmDiaphragm• QuadricepsQuadriceps

– rectus femorisrectus femoris– vastus medialisvastus medialis– vastus lateralisvastus lateralis

Anterior Skeletal Anterior Skeletal MusclesMuscles

Selected Superficial Selected Superficial Skeletal Muscles Skeletal Muscles (Posterior View)(Posterior View)

• TrapeziusTrapezius• Triceps brachiiTriceps brachii• GastrocnemiusGastrocnemius• Latissimus dorsiLatissimus dorsi

• Hamstring GroupHamstring Group– semimembranosusemimembranosu

ss– biceps femorisbiceps femoris– semitendinosussemitendinosus

• Gluteus maximusGluteus maximus

Posterior Skeletal Posterior Skeletal MusclesMuscles

Muscle Diseases and Muscle Diseases and DisordersDisorders

Myalgia (Fibromyalgia)Myalgia (Fibromyalgia)

• Painful disorders of muscles, Painful disorders of muscles, tendons, and surrounding soft tendons, and surrounding soft tissuetissue

FibromyalgiaFibromyalgia

You Tube Video called “Fibromyalgia Documentary Sneak Peek” that can be found atYou Tube Video called “Fibromyalgia Documentary Sneak Peek” that can be found at http://www.youtube.com/watch?v=ehzDYI70dLw&feature=related http://www.youtube.com/watch?v=ehzDYI70dLw&feature=related

Muscular DystrophiesMuscular Dystrophies

• Muscle destroying diseases Muscle destroying diseases characterized by the degeneration characterized by the degeneration of individual muscle fibersof individual muscle fibers

• Leads to progressive atrophy of Leads to progressive atrophy of skeletal musclesskeletal muscles

• Due to a genetic defectDue to a genetic defect

Muscular DystrophyMuscular DystrophyYou Tube video called Duchenne Muscular Dystrophy found at http://www.youtube.com/watch?v=6wuTEFRhh-I&feature=relatedYou Tube video called Duchenne Muscular Dystrophy found at http://www.youtube.com/watch?v=6wuTEFRhh-I&feature=related

Shin SplintsShin Splints• Pain in the lower legPain in the lower leg• Tendonitis of the tibialis posterior muscleTendonitis of the tibialis posterior muscle• Inflammation of the periosteumInflammation of the periosteum• Stress fracture of the tibiaStress fracture of the tibia• Exaggerated enlargement of muscles Exaggerated enlargement of muscles

within the epimysium within the epimysium • Pulling away of the periosteum from the Pulling away of the periosteum from the

underlying boneunderlying bone• Treatment:Treatment:

– RICERICE– strengthen tibialis anterior musclestrengthen tibialis anterior muscle

Shin SplintsShin SplintsYou Tube Video called “How to treat shin splints” found at http://www.youtube.com/watch?v=ZVgSxrISOwAYou Tube Video called “How to treat shin splints” found at http://www.youtube.com/watch?v=ZVgSxrISOwA

SprainsSprains• the forcible wrenching or twisting the forcible wrenching or twisting

of a joint with partial or complete of a joint with partial or complete rupture or injury to joint rupture or injury to joint attachments without dislocationattachments without dislocation

• 1st Degree Sprain = stretching of 1st Degree Sprain = stretching of ligamentsligaments

• 2nd Degree Sprain = partial 2nd Degree Sprain = partial tearing of ligamentstearing of ligaments

• 3rd Degree Sprain = complete tear 3rd Degree Sprain = complete tear of ligamentsof ligaments

Sprained AnkleSprained AnkleYou Tube video called “Baby Boomers at risk for ankle sprains, chronic ankle instability found at You Tube video called “Baby Boomers at risk for ankle sprains, chronic ankle instability found at http://www.youtube.com/watch?v=Ix1e7tkzN3o&feature=relatedhttp://www.youtube.com/watch?v=Ix1e7tkzN3o&feature=related

StrainsStrains

• pulling or overstretching a muscle pulling or overstretching a muscle • soft tissue (Muscle) injurysoft tissue (Muscle) injury

Muscle StrainsMuscle StrainsYou Tube Video called “Pulling a Hamstring Muscle What is a Pulled Hamstring Video About com” that can be found at You Tube Video called “Pulling a Hamstring Muscle What is a Pulled Hamstring Video About com” that can be found at http://www.youtube.com/watch?v=t4HLKQWo1Ts&feature=related.http://www.youtube.com/watch?v=t4HLKQWo1Ts&feature=related.