The Muscular SystemThe Muscular System

• Muscles are responsible for all types of body Muscles are responsible for all types of body movementmovement

• Muscle Functions:Muscle Functions:– MovementMovement– Maintain postureMaintain posture– Stabilize jointsStabilize joints– HeatHeat

• Three basic muscle types found in the body:Three basic muscle types found in the body:– Smooth muscle (Visceral)Smooth muscle (Visceral)– Cardiac muscleCardiac muscle– Skeletal muscleSkeletal muscle

Characteristics of Characteristics of MusclesMuscles

• Muscle cells are Muscle cells are elongatedelongated

• Contraction of muscles Contraction of muscles is due to the movement is due to the movement of microfilaments – of microfilaments – many cells contracting many cells contracting at the same timeat the same time

• All muscles share some All muscles share some terminologyterminology– Prefix Prefix myomyo refers to refers to

musclemuscle

Smooth MuscleSmooth Muscle Characteristics: Characteristics:

How blood and food moveHow blood and food move• No striationsNo striations• Spindle-shaped Spindle-shaped

cellscells• Single nucleusSingle nucleus• Involuntary – no Involuntary – no

conscious controlconscious control• Found mainly in the Found mainly in the

walls of hollow walls of hollow organs (blood organs (blood vessels, intestines)vessels, intestines)

Figure 6.2a

Cardiac MuscleCardiac Muscle Characteristics:Characteristics:

What makes your heart What makes your heart beat?beat?• StriationsStriations

• Usually only one Usually only one nucleusnucleus

• Cells joined to Cells joined to each other at an each other at an intercalated discintercalated disc

• InvoluntaryInvoluntary• Found Found onlyonly in the in the

heartheartFigure 6.2b

Skeletal MuscleSkeletal Muscle Characteristics:Characteristics:

Moving your bones!Moving your bones!• Most are attached by tendons to bones Most are attached by tendons to bones

– Remember “Remember “ttendons endons ttug” ug”

• Cells have more than one nucleusCells have more than one nucleus• Striated – have visible bandingStriated – have visible banding• Voluntary – subject to conscious Voluntary – subject to conscious

controlcontrol• Cells are surrounded and bundled by Cells are surrounded and bundled by

connective tissueconnective tissue

Connective Tissue Connective Tissue Wrappings of Skeletal Wrappings of Skeletal

MuscleMuscle• EndomysiumEndomysium – –

around single around single muscle fibermuscle fiber

• PerimysiumPerimysium – – around a bundle around a bundle of fibersof fibers

• EpimysiumEpimysium – – covers the entire covers the entire skeletal muscleskeletal muscle

Figure 6.1

Skeletal Muscle Skeletal Muscle AttachmentsAttachments

• Epimysium blends into a connective tissue Epimysium blends into a connective tissue attachment; the tendon – a cord-like attachment; the tendon – a cord-like structurestructure

• Sites of muscle attachmentSites of muscle attachment– BonesBones– CartilagesCartilages– Connective tissue coveringsConnective tissue coverings

Animation: Animation: http://www.wisc-online.com/objects/index_tj.asp?objID=AP13904

Contraction of a Skeletal Contraction of a Skeletal MuscleMuscle• Video

• Muscle fiber contraction is “all or none”Muscle fiber contraction is “all or none”• Within a skeletal muscle, not all fibers may Within a skeletal muscle, not all fibers may

be stimulated during the same intervalbe stimulated during the same interval• Different combinations of muscle fiber Different combinations of muscle fiber

contractions may give differing responsescontractions may give differing responses• Graded responses – different degrees of Graded responses – different degrees of

skeletal muscle shorteningskeletal muscle shortening• Must have ATP in order to contractMust have ATP in order to contract

Muscle Response to Muscle Response to Strong StimuliStrong Stimuli

• Muscle force depends upon the Muscle force depends upon the number of fibers stimulatednumber of fibers stimulated

• More fibers contracting results in More fibers contracting results in greater muscle tensiongreater muscle tension

• Muscles can continue to contract Muscles can continue to contract unless they run out of energy (ATP)unless they run out of energy (ATP)

Muscle Fatigue and Muscle Fatigue and Oxygen DebtOxygen Debt

• When a muscle is fatigued, it is unable When a muscle is fatigued, it is unable to contractto contract

• The common reason for muscle fatigue The common reason for muscle fatigue is oxygen debtis oxygen debt– Oxygen must be returned to tissue to Oxygen must be returned to tissue to

remove oxygen debtremove oxygen debt– Oxygen is required to get rid of Oxygen is required to get rid of

accumulated lactic acidaccumulated lactic acid• Increasing acidity (from lactic acid) and Increasing acidity (from lactic acid) and

lack of ATP causes the muscle to lack of ATP causes the muscle to contract lesscontract less

Muscles and Body Muscles and Body MovementsMovements

• Movement is attained Movement is attained due to a muscle due to a muscle moving an attached moving an attached bonebone

• Muscles are attached Muscles are attached to at least two pointsto at least two points– Origin – attachment to Origin – attachment to

an immoveable bonean immoveable bone– Insertion – attachment Insertion – attachment

to a movable boneto a movable bone

Figure 6.12

Ordinary Body Ordinary Body MovementsMovements

• Flexion – decreases the angle between Flexion – decreases the angle between two adjacent body segmentstwo adjacent body segments

• Extension – increases the angle between Extension – increases the angle between two adjacent body segmentstwo adjacent body segments

• Rotation – the bone distal to the joint is Rotation – the bone distal to the joint is moved either toward (medial) or away moved either toward (medial) or away from (lateral) the midlinefrom (lateral) the midline

• Abduction – movement of a body part Abduction – movement of a body part away from the midlineaway from the midline

• Adduction – movement of a body part Adduction – movement of a body part back toward the midlineback toward the midline

• Circumduction – a combination of flexion, Circumduction – a combination of flexion, abduction, extension, and adductionabduction, extension, and adduction

http://www.med.umich.edu/lrc/hypermuscle/hyper.html

Body MovementsBody Movements

Figure 6.13a–c

Body MovementsBody Movements

Body MovementsBody Movements

Figure 6.13d

Naming of Skeletal Naming of Skeletal MusclesMuscles

• Direction of muscle fibersDirection of muscle fibers– Example: Example: rectusrectus (straight) (straight)

• Relative size of the muscleRelative size of the muscle– Example: Example: maximusmaximus (largest) (largest)

• Location of the muscleLocation of the muscle– Example: many muscles are named for Example: many muscles are named for

bones (e.g., bones (e.g., temporalistemporalis))• Number of originsNumber of origins

– Example: Example: tricepstriceps (three heads) (three heads)

Naming of Skeletal Naming of Skeletal MusclesMuscles

• Location of the muscle’s origin and Location of the muscle’s origin and insertioninsertion– Example: Example: sternosterno (on the sternum) (on the sternum)

• Shape of the muscleShape of the muscle– Example: Example: deltoiddeltoid (triangular) (triangular)

• Action of the muscleAction of the muscle– Example: Example: flexorflexor and and extensorextensor (flexes or (flexes or

extends a bone)extends a bone)

Head and Neck MusclesHead and Neck Muscles

Figure 6.15

Trunk MusclesTrunk Muscles

Figure 6.16

Deep Trunk and Arm Deep Trunk and Arm MusclesMuscles

Figure 6.17

Muscles of the Pelvis, Hip, Muscles of the Pelvis, Hip, and Thighand Thigh

Figure 6.19c

Muscles of the Lower LegMuscles of the Lower Leg

Figure 6.20

Superficial Muscles: Superficial Muscles: AnteriorAnterior

Figure 6.21

Superficial Muscles: Superficial Muscles: PosteriorPosterior

Figure 6.22

Movement Movement Worksheet p.1Worksheet p.1Standing on your toes as in ballet is (1)

of the foot. Walking on your heels is (2).

Winding up for a pitch (as in baseball) can properly be called (3) . To keep your seat when riding a horse, the tendency is to (4) your thighs.In running, the action at the hip joint is (5) in reference to the leg moving forward and (6) in reference to the leg in the posterior position. When kicking a football, the action at the knee is (7) . In climbing stairs, the hip and knee of the forward leg are both (8) .

You have just touched your chin to your chest; this is (9) of the neck.Using a screwdriver with a straight arm requires (10) of the arm. Consider all the movements of which the arm is capable. One often used for strengthening the upper arm and shoulder muscles is (11) .Moving the head to signify “no” is (12) . Action that moves the distal end of the radius across the ulna is (13) . Raising the arms laterally away from the body is called (14) of the arms.When you are cupping your hands in order to hold a bowl of soup, the position is called __(15)__.