FASCIA, MUSCLES, FASCIA, MUSCLES, TENDONSTENDONS

Skeletal Muscle StructureSkeletal Muscle Structure

Origin:Origin:Proximal attachmentProximal attachment

Insertion:Insertion:Distal attachmentDistal attachment

Tendons: Tendons: Peritendineum Peritendineum

Aponeurosis Aponeurosis

Skeletal Muscle HierarchySkeletal Muscle Hierarchy

Myofilament:Myofilament:Thick filamentsThick filaments

Myosin Myosin

Thin filamentsThin filamentsActin Actin

Myofibril:Myofibril:Bundle of myofilamentsBundle of myofilaments

Segmentally arranged into sarcomeresSegmentally arranged into sarcomeres

Skeletal Muscle HierarchySkeletal Muscle Hierarchy

MyofiberMyofiber

Made up of many myofibrilsMade up of many myofibrils

Multinucleated in skeletal musclesMultinucleated in skeletal muscles

= muscle cell= muscle cell FascicleFascicle

Bundle of myofibersBundle of myofibers Muscle Muscle

Composed of several to several hundred Composed of several to several hundred fasciclesfascicles

Connective TissuesConnective Tissues

Endomysium:Endomysium:Surrounds a myofiber Surrounds a myofiber

Perimysium:Perimysium:Surrounds a fascicleSurrounds a fascicle

Connective TissuesConnective Tissues

Epimysium:Epimysium:Covers entire muscleCovers entire muscleBlends in with deep fasciaBlends in with deep fascia

Connective tissue supports provide Connective tissue supports provide physical support and a pathway for nerves physical support and a pathway for nerves and vessels.and vessels.

MyofilamentsMyofilaments

Actin myofilaments (F-actin):Actin myofilaments (F-actin):Polymers of G-actinPolymers of G-actin

Tropomyosin Tropomyosin

TroponinTroponin Myosin filaments:Myosin filaments:

ATPaseATPase

SarcomeresSarcomeres

Z-line (Z-actin):Z-line (Z-actin):Composed of Z-actinComposed of Z-actinMarks ends of Z-actinMarks ends of Z-actin

I bands:I bands:Part of a sarcomere composed entirely of Part of a sarcomere composed entirely of actinactin

SarcomeresSarcomeres

A band:A band:Part of a sarcomere composed of both Part of a sarcomere composed of both

actin and myosinactin and myosin

H band:H band:Part of a sarcomere composed entirely of Part of a sarcomere composed entirely of

myosinmyosin

Sliding Filament TheorySliding Filament Theory

During a contraction:During a contraction:I band and H band shortenI band and H band shorten

A band remains the same lengthA band remains the same length

Sliding occurs when ATPase heads of Sliding occurs when ATPase heads of myosin attach to actin via troponin and myosin attach to actin via troponin and swivel.swivel.

MyofiberMyofiber

Sarcoplasmic reticulum:Sarcoplasmic reticulum:Equivalent to endoplasmic reticulum of Equivalent to endoplasmic reticulum of

most most cells.cells.T-tubules:T-tubules:

Tubular extensions of the muscle fiber Tubular extensions of the muscle fiber membrane that extend down into the membrane that extend down into the cytoplasm (saracoplasm).cytoplasm (saracoplasm).

Conduct action potential from cell Conduct action potential from cell membrane membrane surface to interior.surface to interior.

MyofiberMyofiber

Cisternae:Cisternae:Saccular extensions of the sarcoplasmic Saccular extensions of the sarcoplasmic reticulum that release calcium ions in reticulum that release calcium ions in

response to action potential.response to action potential.

Calcium ions trigger sliding of myosin and Calcium ions trigger sliding of myosin and actin filaments, resulting in a contraction.actin filaments, resulting in a contraction.

Myofiber TypeMyofiber Type

The myofiber type (red or white) depends The myofiber type (red or white) depends on innervation.on innervation.

All myofibers in a motor unit are of the All myofibers in a motor unit are of the same type.same type.

Dark (red) FibersDark (red) Fibers

Fatigue resistantFatigue resistantContract slowly (slow twitch)Contract slowly (slow twitch)Rely on oxidative phosphorylationRely on oxidative phosphorylationHave a large number of mitochondriaHave a large number of mitochondriaHave a high concentration of myoglobinHave a high concentration of myoglobinHave a low concentration of ATPaseHave a low concentration of ATPase

Light (white) FibersLight (white) Fibers

Fatigue easilyFatigue easilyContract rapidly (fast twitch)Contract rapidly (fast twitch)Rely on glycolysisRely on glycolysisHave a small number of mitochondriaHave a small number of mitochondriaHave a low concentration of myoglobinHave a low concentration of myoglobinHave a high concentration of ATPaseHave a high concentration of ATPase

Neuromuscular JunctionsNeuromuscular Junctions

Components:Components:Presynaptic membrane:Presynaptic membrane:

Terminal end of motor neuron.Terminal end of motor neuron.

Synaptic cleftSynaptic cleft

Postsynaptic membrane:Postsynaptic membrane:Sarcolemma (cell membrane of myofiber)Sarcolemma (cell membrane of myofiber)

Motor UnitMotor Unit

Consists of a motor neuron and all the Consists of a motor neuron and all the myofibers it innervatesmyofibers it innervates

Units for fine control have fewer fibersUnits for fine control have fewer fibers

Units for gross control have many fibersUnits for gross control have many fibers

Muscle ClassificationMuscle Classification

Fiber arrangementFiber arrangementShapeShapeOrigin and insertionOrigin and insertionFunctionFunction

Fiber ArrangementFiber Arrangement Straight:Straight:

Example: rectus abdominisExample: rectus abdominis Fusiform:Fusiform:

Example: biceps brachiiExample: biceps brachii Unipennate:Unipennate:

Example: palmar interosseous musclesExample: palmar interosseous muscles Bipennate:Bipennate:

Example: dorsal interosseous musclesExample: dorsal interosseous muscles Multipennate:Multipennate:

Example: deltoid muscleExample: deltoid muscle

Muscle ShapeMuscle Shape

DeltoidDeltoid

TrapeziusTrapezius

Muscle Origin/InsertionMuscle Origin/Insertion

CoracobrachialisCoracobrachialis

SternocleidomastoidSternocleidomastoid

Muscle FunctionMuscle Function

Pronater teresPronater teres

Extensor digitorumExtensor digitorum

ContractionContraction

Definition:Definition:A contraction is a muscle’s response to a A contraction is a muscle’s response to a stimulus.stimulus.

Types of contraction:Types of contraction:Isotonic (the length of the muscle Isotonic (the length of the muscle

changes)changes)Concentric (length decreases)Concentric (length decreases)Eccentric (length increases)Eccentric (length increases)

Isometric (the length of the muscle stays Isometric (the length of the muscle stays the the same)same)

Types of ActionTypes of Action

Agonist (prime mover):Agonist (prime mover):A muscle that primarily carries out the A muscle that primarily carries out the

desired action.desired action.Antagonist:Antagonist:

A muscle that opposes the agonist.A muscle that opposes the agonist.Synergist:Synergist:

A muscle that eliminates the unwanted A muscle that eliminates the unwanted action of the agonist.action of the agonist.

Types of ActionTypes of Action

Fixator:Fixator:A muscle that stabilizes the origin of A muscle that stabilizes the origin of

another another muscle.muscle.Note: a single muscle can be all the above Note: a single muscle can be all the above

at one time or another.at one time or another.

InsufficiencyInsufficiency

Refers to the inability of a multijoint muscle Refers to the inability of a multijoint muscle to maximally contract simultaneously over to maximally contract simultaneously over all joints crossed.all joints crossed.

Active:Active:Refers to the agonistRefers to the agonist

Passive:Passive:Refers to the antagonistRefers to the antagonist

Smooth MuscleSmooth Muscle

Synonyms:Synonyms:VisceralVisceralInvoluntaryInvoluntary

Found in:Found in:Walls of visceral tubes (intestines, etc.)Walls of visceral tubes (intestines, etc.)Associated with hair folliclesAssociated with hair folliclesAround glandular structuresAround glandular structuresIn walls of blood vesselsIn walls of blood vessels

Smooth Muscle CharacteristicsSmooth Muscle Characteristics

Bundles of sheets of individual cells.Bundles of sheets of individual cells.Not striated (smooth).Not striated (smooth).Cells are primarily elongated and tapered.Cells are primarily elongated and tapered.Mononucleated.Mononucleated.

Smooth Muscle CharacteristicsSmooth Muscle Characteristics

Nuclei are centrally located in each cell.Nuclei are centrally located in each cell.Does not conduct action potential.Does not conduct action potential.Cells connected by gap junctions.Cells connected by gap junctions.Not under voluntary control.Not under voluntary control.

Cardiac Muscle TissueCardiac Muscle Tissue

Found only in walls of heart.Found only in walls of heart.Characteristics:Characteristics:

Striated (sarcomeres)Striated (sarcomeres)

Mononucleated cells:Mononucleated cells:May branchMay branch

Intercalated discs:Intercalated discs:Sites of transfer of stimulus between Sites of transfer of stimulus between

adjacent adjacent cells.cells.