Muscular SystemMuscular System

FunctionsFunctions

Muscle TissueMuscle Tissue

•Refers to all the contractile Refers to all the contractile tissues of the body.tissues of the body.

•Skeletal=attached to Skeletal=attached to skeleton.skeleton.

•Cardiac= heart musclesCardiac= heart muscles•Smooth= muscles of Smooth= muscles of

organsorgans

Smooth MuscleSmooth Muscle

• Cells are small spindle shapedCells are small spindle shaped

• Non-striatedNon-striated (striations are dark lines (striations are dark lines of tissue )of tissue )

• Involuntary muscleInvoluntary muscle

• Found in organ groups..Example: Found in organ groups..Example: intestinal, bladder, blood vessels.intestinal, bladder, blood vessels.

• Muscle contractions are rhythmic and Muscle contractions are rhythmic and slow.slow.

Cardiac MuscleCardiac Muscle

• Requires continuous O2Requires continuous O2

• Only in the heartOnly in the heart

• StriatedStriated

• InvoluntaryInvoluntary

• Muscle contractions are Muscle contractions are rhythmic & automaticrhythmic & automatic

Skeletal MuscleSkeletal Muscle• Attached to the bones of Attached to the bones of

skeletonskeleton

• Voluntary muscle…contains Voluntary muscle…contains nerves under voluntary controlnerves under voluntary control

• Composed of bundles of Composed of bundles of muscle cellsmuscle cells– Each cell is Multinucleated.Each cell is Multinucleated.– Each cell is a muscle fiberEach cell is a muscle fiber– Cell Cell

membrane=SARCOLEMMAmembrane=SARCOLEMMA– Cytoplasm=SARCOPLASMCytoplasm=SARCOPLASM

Characteristics….Characteristics….

•ContractibilityContractibility: muscles : muscles shorten and tighten…shorten and tighten…which in turn, brings the which in turn, brings the two ends of the bone two ends of the bone closer together..which is closer together..which is movementmovement....

Characteristics…cont’Characteristics…cont’

• ExcitabilityExcitability:: or irritability.. or irritability.. The ability to respond to The ability to respond to certain stimuli..producing certain stimuli..producing signals called action signals called action potentials= impulses..(nerve potentials= impulses..(nerve impulses)impulses)

• Extensibility:Extensibility: The ability of The ability of the muscle to be stretched. the muscle to be stretched.

Characteristics…cont’Characteristics…cont’

•Elasticity: Elasticity: The ability The ability for a muscle to return for a muscle to return to its original shape to its original shape when relaxing.when relaxing.

Attachments…..Attachments…..

– OriginOrigin:: point where point where muscle is attached to muscle is attached to bone that moves very bone that moves very littlelittle

– InsertionInsertion:: point where point where muscle ismuscle is attached to bone attached to bone that moves.that moves.

– Belly:Belly: central part of the central part of the musclemuscle

Contraction of Skeletal Contraction of Skeletal MuscleMuscle

• Movement occurs as a Movement occurs as a result of 2 major events:result of 2 major events:

• Nerve stimulation : Nerve stimulation : message sent thru nerves message sent thru nerves to the muscle..to the muscle..

• Action potential: the Action potential: the muscle receives the stimuli, muscle receives the stimuli, and contracts as a result.and contracts as a result.

Muscle GroupsMuscle Groups

•Head and NeckHead and Neck•Upper ExtremitiesUpper Extremities•TrunkTrunk

– Thorax & AbdomenThorax & Abdomen– Posterior & AnteriorPosterior & Anterior

•Lower extremitiesLower extremities

Major Muscles of theMajor Muscles of theHead & Neck…..Head & Neck…..

• Temporalis: at the templeTemporalis: at the temple• Frontalis: foreheadFrontalis: forehead• Masseter: cheekMasseter: cheek• Orbicularis oculi: around the eyeOrbicularis oculi: around the eye• Sternocleidomastoid: Behind the Sternocleidomastoid: Behind the

ear to the clavicleear to the clavicle• Trapezius: Back of the head Trapezius: Back of the head

(occipital) to the shoulder.(occipital) to the shoulder.• Orbicularis oris: around the Orbicularis oris: around the

mouthmouth• Zygomaticus major: cheekbone Zygomaticus major: cheekbone

to orbicularis oristo orbicularis oris• Nasalis: muscles of the noseNasalis: muscles of the nose

IntercostalIntercostalss

More to come…..More to come…..