Muscular SystemMuscular System

IntroductionIntroduction

You have over 600 skeletal muscles (656-You have over 600 skeletal muscles (656-850 depending on who you talk to)850 depending on who you talk to)

Muscles account for 40% of our body Muscles account for 40% of our body weightweight

Types of muscle tissueTypes of muscle tissue

Cardiac: Cardiac: Walls of the heartWalls of the heart InvoluntaryInvoluntary striatedstriated

Smooth or visceralSmooth or visceral Found in internal organs: respiratory tract, Found in internal organs: respiratory tract,

digestive tract, blood vessels and eyesdigestive tract, blood vessels and eyes Long circular fibers – peristalsisLong circular fibers – peristalsis Smooth (no striations)Smooth (no striations) involuntaryinvoluntary

Skeletal or striatedSkeletal or striated Attached to the bones to cause skeletal Attached to the bones to cause skeletal

movementmovement Striated Striated VOLUNTARYVOLUNTARY

Functions of Skeletal MuscleFunctions of Skeletal Muscle

Produce skeletal movementProduce skeletal movement Maintain posture and body movement Maintain posture and body movement

(muscle tone)(muscle tone) Protect soft tissue: abdominal wall and Protect soft tissue: abdominal wall and

pelvic floorpelvic floor Maintain body temperature: ex. shiveringMaintain body temperature: ex. shivering

Characteristics of Muscle Characteristics of Muscle TissueTissue

Irritability/excitability: ability of a muscle to Irritability/excitability: ability of a muscle to respond to a stimulus—nerve impulserespond to a stimulus—nerve impulse

Contractibility: when stimulated muscles Contractibility: when stimulated muscles respond by contractingrespond by contracting

Extensibility: ability to be stretchedExtensibility: ability to be stretched Elasticity: ability to return to its normal Elasticity: ability to return to its normal

shape after being stretched or contractedshape after being stretched or contracted

Muscle TissueMuscle Tissue

Actin: protein which forms the thin Actin: protein which forms the thin filamentsfilaments

Myosin: protein which forms the thick Myosin: protein which forms the thick filamentsfilaments

Myofibril: made up of actin and myosin Myofibril: made up of actin and myosin myofilamentsmyofilaments

Muscle fiber (muscle cell): groups of Muscle fiber (muscle cell): groups of myofibrils encased in the endomysium myofibrils encased in the endomysium

Fasciculus: groups of muscle fibers Fasciculus: groups of muscle fibers encased in the perimysiumencased in the perimysium

Skeletal muscle: groups of fasiculi Skeletal muscle: groups of fasiculi encased in the epimysiumencased in the epimysium

Sliding Filament TheorySliding Filament Theory

Actin: thin protein filaments attached z-Actin: thin protein filaments attached z-lineslines

Myosin: thick protein filaments, myosin Myosin: thick protein filaments, myosin heads attach to actin and contract, brining heads attach to actin and contract, brining the z-lines closer togetherthe z-lines closer together

Sarcomere: functional unit of the myofibril Sarcomere: functional unit of the myofibril (runs from z-line to z-line) 1 myofibril can (runs from z-line to z-line) 1 myofibril can have 10,000 or more sarcomerehave 10,000 or more sarcomere

http://biology.kenyon.edu/courses/biol105/html/muscle2.jpg

Types of Muscle ContractionTypes of Muscle Contraction

Isometric: same length – ex. Wall sitsIsometric: same length – ex. Wall sits Concentric: muscle shortens while Concentric: muscle shortens while

contracting: ex. Bicep curlcontracting: ex. Bicep curl Eccentric: muscle lengthens while Eccentric: muscle lengthens while

contracting: bicep as you are lowering the contracting: bicep as you are lowering the weightweight

Strength of Muscle ContractionStrength of Muscle Contraction

Size: the larger the muscle the greater the Size: the larger the muscle the greater the strength of the contractionstrength of the contraction

Number of fibers: the more fibers that are Number of fibers: the more fibers that are recruited the greater the contractionrecruited the greater the contraction

Neuromuscular efficiency: how well the Neuromuscular efficiency: how well the nerve communicates with the musclenerve communicates with the muscle

Biomechanical factors: the angle of the Biomechanical factors: the angle of the jointjoint

Fast twitch v. Slow twitch: Fast twitch v. Slow twitch: Fast twitch muscle: quick forceful contraction Fast twitch muscle: quick forceful contraction

but fatigues quicklybut fatigues quickly Slow twitch: slow rate of contraction over long Slow twitch: slow rate of contraction over long

period of time: resist fatigueperiod of time: resist fatigue Level of physical activity: the more active Level of physical activity: the more active

the greater the contractionthe greater the contraction Overtraining: overtraining can lead to a Overtraining: overtraining can lead to a

decrease in contraction strengthdecrease in contraction strength

Points of AttachmentPoints of Attachment

Origin: less moveable attachment point, Origin: less moveable attachment point, usually more proximalusually more proximal

Insertion: more moveable attachment Insertion: more moveable attachment point, usually distalpoint, usually distal

Skeletal muscles are attached to bones by Skeletal muscles are attached to bones by tendonstendons

How Muscles are NamedHow Muscles are Named

Origin and insertion: sternocleidomastoid, Origin and insertion: sternocleidomastoid, is named for its attachment to the sternum, is named for its attachment to the sternum, clavicle, and mastoid processclavicle, and mastoid process

Location or region:Location or region: Pectoralis – chestPectoralis – chest Gluteus – buttocksGluteus – buttocks Brachii – armBrachii – arm Abdominus – abdomenAbdominus – abdomen Femoris -- femurFemoris -- femur

Action: flexor, extensor, adductor, Action: flexor, extensor, adductor, abductorabductor

Fibers: the direction that the fibers runFibers: the direction that the fibers run Rectus – straight, rectus abdominisRectus – straight, rectus abdominis Tranverse – across, transversus abdominusTranverse – across, transversus abdominus Oblique – diagonal, external obliqueOblique – diagonal, external oblique Obiqularis – circular, obiqularis orisObiqularis – circular, obiqularis oris

DivisionsDivisions Bi – twoBi – two Tri – threeTri – three Quad -- fourQuad -- four

Size: Size: Vastus: Huge, vastus lateralisVastus: Huge, vastus lateralis Maximus: large, gluteus maximusMaximus: large, gluteus maximus Minimus: small, gluteus minumusMinimus: small, gluteus minumus Longus: long, abductor pollicus longusLongus: long, abductor pollicus longus Brevis: short, abductor pollicus brevisBrevis: short, abductor pollicus brevis

ShapeShape Deltiod: triangularDeltiod: triangular Rhomboid: rhombusRhomboid: rhombus Trapezius: trapezoidTrapezius: trapezoid

Categories Based on ActionCategories Based on Action

Agonists: the prime mover, the muscle Agonists: the prime mover, the muscle whose primary function is that particular whose primary function is that particular movementmovement

Synergist: helper, a muscle who assists Synergist: helper, a muscle who assists the agonist in that movementthe agonist in that movement

Anatagonist: a muscle who has the Anatagonist: a muscle who has the opposite movement of the agonistopposite movement of the agonist

Example: for the movement of elbow Example: for the movement of elbow flexionflexion Agonist: biceps brachiiAgonist: biceps brachii Synergist: brachioradialisSynergist: brachioradialis Antagonist: triceps brachiiAntagonist: triceps brachii