K Class 5 TG2 Muscular System Review

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Kinesiology

FES 4

th

Ed Chapter 9 p. 283



Functions of Muscular System



Skeletal muscle is connected to bone It is considered voluntary or under conscious

control of the cerebrum

Involuntary movements are also possiblesince sometimes reflexes (protectivemechanisms that occur without thought) willcause skeletal muscle to contract.



The primary function of skeletal muscle is toexert a pull on the bones which createsmotion.

The contractions of skeletal muscles lift ourfeet, purse our lips for whistling, and expandthe ribcage during breathing.

Skeletal muscle is striated & produces very

strong, rapid contractions Its fibers fatigue more rapidly than those of

smooth or cardiac muscle.



Skeletal muscles are fragile & are vulnerableto damage.

They have a limited ability to regeneratethemselves after injury.

However, the way muscles cells are bundledtogether & reinforced with connective tissue,protects them during strong musclecontractions.

The connective tissue acts as envelopeswhich then converge to make tendons whichattach the muscles to the bones they move.



Skeletal muscles can remain upright againstgravity.

They can keep your head up and centered,your trunk straight and erect, and your hipsand knees aligned over your feet.

Skeletal muscle can also adjust and respondto changes in posture, as when you lean over

or stand up from a chair. These postural muscles cannot rest as long

as you are awake and upright.



Skeletal muscles protect underlyingstructures in areas where bones do not.

The abdomen is not protected by theskeleton so 4 strong abdominal musclesprotect the underlying organs while allowingfree movement of the trunk.



As skeletal muscles contract to producemovement, they also produce body heat.

This production of heat is called

thermogenesis. Approximately ¾ of the energy created by

muscle tissue is used as body heat.



Cardiac muscle is responsible for driving thecardiovascular system but skeletal musclesalso play a role.

The contractions of skeletal muscles helppropel the circulation of lymph & venousblood.

The pumping of the heart keeps the pressure

within arteries high, but both lymphaticvessels & veins have relatively low pressure.



They require help from the contraction ofsurrounding muscles to keep their fluidsmoving forward.

This is especially important where thesefluids must flow upward against gravitysuch as in the legs.



Muscle Fiber Directions



Arrangements: these muscles have fibers ofequal length that do not intersect

This arrangement:

◦ Enables the entire muscle to shorten equally& in the same direction

◦ Maximizes range of motion

Most muscles in the arm are parallel.

Types: Strap, Fusiform, Circular, Triangular, &Spiral



Rectus Abdominus

Long muscle withconsistent width

Examples: Sartorius,quadratus lumborum,

& rectus abdominus Some sources refer to

rectus abdominus as amulti-belly muscle.



Coracobrachialis

Have a thick centralbelly with tapered ends

The tapered ends applyforce to specific bonylandmarks

Examples: brachialis,biceps brachii &coracobrachialis

Most muscles in body

are fusiform



Orbicularis oculi

These musclessurround an openingto form a sphincter

They are designed tocontract & close

passageways or relax& open them

Examples: Orbicularisoris, orbicularis oculi& sphincter ani of

anus.



The fibers of these muscles start with abroad base then converge to a single point.

This fan-shaped arrangement allows themto diversify their actions, creating multiple

movement possibilities. These muscles can pull in different

directions depending upon which fibers arerecruited.

Examples: Deltoid, pectoralis major &trapezius with their multiple & sometimesopposing actions.



Pectoralis Major Trapezius



Latissimus dorsi

Some sources referto muscles thathave a twistedarrangement as

spiral muscles

Examples:Latissimus dorsi &

trapezius



These muscles are feather-shaped withshorter muscle fibers intersecting a centraltendon.

This arrangement maximizes the number offibers in one area.

More muscle fibers mean greater cross-sectional area & greater force production by

these types of muscles. Types: Unipennate, Bipennate & Multipennate







Extensor Digitorum

Longus

The muscle fibers runobliquely from one sideof a central tendon.

These muscles look likehalf of a feather.

The arrangement allowsstrong force productionfrom one direction.

Examples: lumbricals,tibialis posterior &

extensor digitorum

longus



Rectus femoris

The muscle fibers runobliquely along bothsides of a central tendon.

These muscles look like afull feather.

Very strong musclecontractions are possiblesince the central tendonis pulled from 2

directions. Example: Rectus femoris



Deltoid

These muscles havemultiple tendons withoblique fibers on bothsides.

The muscle fibersconnect the tendons &pull from manydirections.

Example: Deltoid



Skeletal Muscle Properties



Ability to stretch without sustaining damage whichallows muscles to lengthen when relaxed.

This is important because muscles usually work inopposite directions as they produce force whilemaintaining stability & balance at joints.

If one muscle is shortening, its opposite must relax &lengthen to allow the joint to move in the intendeddirection.

For example, when the anterior muscles of yourupper arm (flexors) shorten, the posterior muscles ofyour upper arm (extensors) must relax & lengthen.

Without extensibility, the lengthening muscle wouldbe damaged.



Ability to return to its original shape afterlengthening or shortening.

As muscle tissue performs its variousfunctions, its shape changes or deforms.

Once the work is completed, the muscletissue can rest & resume its original form.

This property allows a muscle to maintain a

specific shape when at rest.



Muscle tissue can respond to a stimulus byproducing electrical signals.

In response to an event such as a touch or adecision to move, nerves at their junction withmuscles release specialized chemicals(neurotransmitters).

The neurotransmitters cause the spread of anelectrical signal (action potential) that in turntriggers a series of events that lead to a muscle

contraction. Without this ability to respond to the nervous

system, muscle would not be able to contract &function.



The muscle’s ability to propagate transmit or

spread) electrical signals, including action

potentials.

Once muscle tissue is ‘excited’ by the

nervous system, it must carry the electricalsignal to the inner cell structures.

Conductivity allows the action potential to be

transmitted along the muscle cell, activatingthe tissue & initiating a muscle contraction.



The ability to shorten and thicken in responseto a specific stimulus.

Here the stimulus is the action potentialinitiated by the nervous system.

The ability to shorten is a unique feature ofmuscle tissue

Specialized proteins (myosin and actin) within

muscle tissue interact to shorten and thickenmuscles, generating a force.

Our bodies depend on this force to move.



Anatomy of Skeletal Muscle



Macroscopic or Gross Anatomy





Connective Tissue



Connective tissue

structures support,

protect separate

portions of muscles

whole muscles.

Endomysium: sheath

of connective tissue

that wraps individual

muscle cells or fibers

or myofibers.



Perimysium: layer

of connective tissue

that encircles

holds together

bundles of muscle

cells called fascicles



Epimysium:

◦An envelope

surrounding all the

muscle is a part of

the deep fascia

network◦ Converges to form a

tendon that connects

the muscle to the

bone

◦ Musculotendinous

junction is the point

where muscle belly

ends tendon starts



Portion of the

muscle between

the tendons

‘Meaty’ portion

of the muscle



Origin:◦ Usually the heavier & proximal attachment

◦ Attachment that does not move or is most stable

Insertion:

◦ Usually the lighter & distal attachment◦ Attachment that moves or is most mobile

◦Greatest amount of movement takes place at

insertion

Aponeurosis:

◦ Broad sheet-like tendon

◦ Broad sheet of fibrous connective tissue



Large blood vessels

nerves are

enclosed within the

epimysium

Capillaries nerve

fiber endings are

wrapped within the

endomysium where

they interact with

individual muscle

cells



Microscopic Anatomy





Sarcolemma:

◦Surrounds the entire

muscle cell

◦ Serves as a cell

membrane regulates

chemical transport into

and out of the cell.

Sarcoplasm:

◦ Gelatinous substance

that surrounds the

structures within the

muscle cell

◦Functions as the

cytoplasm of the cell



Mitochondria:

produces ATP, a

compound that

stores the energy

needed for muscle

contraction

Nuclei:

contain the

functional

information for the

cell control its

operations



Myofibrils

myofilaments:

Myofibrils are

specialized

contractile proteins

that make skeletal

tissue look striated

(or banded)

Stripes or bands

reflect the two types

of filaments or

myofilaments – actin

myosin



Sarcomeres:

◦ Contain structures from one Z line to the next◦

Functional units of muscle fibers since it is the

shortening of the sarcomere that produces

concentric muscle contractions

Regions of the Sarcomere:◦ Lighter I Band: where the thin filaments or actin

occur alone◦ Darker A band: where the thick or myosin & thin

filaments overlap◦

Z line: The lighter I bands are interrupted by azigzag line called the Z line which marks theborders of the sarcomeres.





Transverse tubules:

◦Transmit nerve impulses

from the sarcolemma to

the cell interior

Sarcoplasmic

reticulum (SR):

◦ Network of fluid-filled

chambers that cover

each myofibril like a lacy

sleeve

◦These chambers store

calcium ions which help

trigger muscle

contractions.



Physiology of Muscle Contraction



Neuromuscular Junction: point of close contactbetween neuron & muscle fibers

Axons of Neurons: long thin structures that reachout from the neuron cell body to transmit anaction potential through its terminal branches to

muscle cells Action potential: nerve impulse that is strong,

invariable, & capable of traveling long distancesin the body – from a neuron in the brain to amuscle cell in a finger.

Synapse or synaptic cleft: gap between the axonbranches & the muscle cell that prevents theaction potential from crossing to the muscle onits own.





Acetylcholine (Ach):

◦ Neurotransmitter that helps the action potential to jump the gap or synapse

◦ Ach is stored in seminal vesicles at the ends of theaxon branches & is released when an action

potential reaches the NMJ◦ Once across the gap, Ach binds to receptors within

the muscle fiber’s sarcolemma

◦ This binding stimulates a new action potential onthe muscle fiber side of the synapse

◦ The new action potential in turn initiates thechemical processes of muscular contraction



A neuron sends an electrical signal calledan action potential down its axon

The signal reaches the ends of the axonbranches, where it stimulates synapticvesicles to release acetylcholine (Ach)

Ach molecules cross the synaptic cleft &bind with receptors in the sarcolemma

A muscle action potential travels along thesarcolemma & down the transverse tubules



Explains how the thick & thin myofilamentsbind & release to produce shortening in thesarcomere in a concentric musclecontraction.

Four contractile proteins are involved:

◦Myosin

◦Actin

◦

Troponin

◦Tropomyosin





Myosin Actin

Makes up thestrands of thethick myofilament

& the roundedends are calledheads whichattach to binding

sites on actin

Makes up thestrands of thethin filament &

has ‘beads’ onlong strands.





Tropomyosin: ◦ Its threads covers the actin ‘beads’◦ As long as the muscle is relaxed, it covers the

binding sites on the actin molecules, preventingthem from participating in a muscle contraction.

◦

Myosin heads attach to these binding sites tomove the actin Troponin:

◦ Tropomyosin threads are studded with &controlled by clusters of Troponin

◦

This protein keeps Tropomyosin in place over theactin binding sites in relaxed muscle & moves outof the way to allow a muscle contraction.



Action potential reachesSarcoplasmic Reticulum &stored calcium ions arereleased into the sarcoplasm.

The calcium ions bind withthe studs of Troponin on the

actin, causing them to ‘moveaside’ the Tropomyosinprotein strands covering thebinding sites on the actin.

Once the binding sites arerevealed, the thin filament is

ready for contraction.



The myosin heads on the thickfilament are charged withenergy from the breakdown ofATP.

This energy binds the myosinheads to the actin filament

creating connections calledcross-bridges. Once cross-bridges are

formed, a ratcheting actioncalled the power stroke occursas the myosin heads, bound toactin, pull the sarcomere

together.



Like a line of rowers in a long boatsimultaneously pulling their oars againstthe water, myosin heads along the thickfilament pull & slide the thin filamenttoward the center of the sarcomere,shortening the strand.

As the myosin heads complete theirpower stroke, they bind with more ATP.This provides the energy necessary for

them to release their hold on the actinstrand.





This process is repeated by alternatingmyosin heads on both sides of the thinfilament along the length of the musclefiber, creating muscle contractions.

Once the thin & thick filaments haveaccomplished muscle contractions, thenerve action potential stops.

Any ACh remaining in the synaptic cleftis broken down and deactivated.



Calcium ions are released from theTroponin & actively pumped back tothe SR using additional energy from

ATP. The Tropomyosin threads realign withthe actin binding sites, preventingfurther formation of cross-bridges.

The muscle then passively returns toits resting length.





http://joellezimprich.wikispaces.com/11--

Muscle+Physiology



Action potential crosses from transversetubules to cell interior.

Calcium ions released from SarcoplasmicReticulum.

Receptor sites on actin exposed as calciumions bind to Troponin.

Charged myosin heads bind to actin

creating cross-bridges. Power strokes pulls ends of sarcomeres

together creating muscle contraction



Factors Affecting Force Production



Motor Neurons: neurons responsible for delivering anelectrical impulse to muscle fibers

Motor Unit:

◦ Consists of a motor neuron all the muscle fibers it

controls

◦ Muscles are typically composed of multiple MUs◦ When MU reaches a muscle, it can synapse with 2-3

or up to 2000 muscle cells but average number is100-200 muscle cells.

◦ Some MUs have few fibers (face & hand) which allowsthem to produce fine movements

◦ Smallest MUs are in muscles that move the eye

◦ Other MUs (thigh) have 1000s of muscle fibers & canproduce powerful movements but lack fine control.





The body can control the amount of forceproduced by a given muscle by varying thenumber & size of MUs recruited

◦ Stimulation of few motor units generates a

small amount of force.◦ Stimulation of all motor units generates

maximal force.



The larger the

motor units

recruited the

number of motor

units recruited

results in the

greater potential

force production.







Some motor units stay activated all the time,creating a minimal amount of tension in restingmuscles that keeps them firm & ready tocontraction.

This tension indicates the strength ofconnection between the nervous system &skeletal muscle.

If muscles are utilized frequently, as withexercise, increased tone may result.

Muscle tone helps maintain posture & jointstability & decreases time needed for muscleforce production.



Excessive tone

that can be

present in

overworked

muscles



Decreased use orinjury can resultin less muscle

tone



A major factor influencing muscle forceproduction

The muscle’s ability to generate force relatesmore closely with a muscle’s thickness than

its total volume. Thicker, shorter muscles generate more force

than longer, thinner muscles.

Cross-sectional area is related to the size ofthe myofibrils.



As myofibrilsbecome largerthrough use(hypertrophy),

muscles increase incross-sectionalarea & can generatemore force.



A decrease in

size of myofibrils

from lack of use



Results in

reduced cross-

sectional area

reduced ability to

generate force



Pennate fiber arrangements generate moretotal force than parallel muscles.

Pennate arrangement allows more musclefibers to reside in a given area.

More muscle fibers increase the muscle’scross-sectional area & ability to generateforce.

Pennate muscles sacrifice ROM for increasedstrength & speed.





A muscle at its resting length has maximumspace to shorten in the sarcomere & thisallows the greatest force production.

As a muscle stretches beyond resting length,

fewer cross-bridges are formed between theactin & myosin & fewer cross-bridges meanless force production.



Skeletal Muscle Fiber Types



Also called slow oxidative fibers; Contract (twitch) slowly but are resistant to

fatigue – they take approximately 1/10 of asecond to reach maximum tension.

They rely on aerobic energy production (usingoxygen).

They are red in color due to their rich blood

supply (highly vascularized).



Slow twitch fibers are utilized for longduration activities (more than 2 minutes) suchas walking and jogging.

Postural muscles that must remain contracted

for extended periods of time are primarily

composed of slow twitch fibers.

Slow-Twitch (red

–

aerobic) fibers contract

more slowly with less intensity but have

more endurance myoglobin.



Generate fast, powerful contractions but

quickly fatigue – take approximately 1/20 ofa second to reach maximum tension. Fibers are larger in diameter than slow twitch

fibers due to a greater number of

myofilaments. More myofilaments means the ability to

produce more force. Fast twitch fibers don’t use oxygen for energy

production – are anaerobic Are a lighter color since they don’t have

blood vessels



Sprinter Climber

Utilize anaerobic energyproduction.

Used for short-durationactivities (less than 2minutes) such assprinting (in the legs of

sprinters) & lifting. Large powerful muscles

are primarily fast twitchfibers.

Contact rapidly

forcefully but fatigue

quickly.



Have characteristics of both fast & slow

twitch They range from red to pink in color.

We can consider intermediate (mixed) fibersas reservists waiting to be called up when &where the need arises.



Type 2 2X size of Type 1





Biceps Brachii

Have a higherpercentage of fast-twitch white fibers

Jump into actionquickly & tire quickly

Usually weaken inresponse to posturalmuscle shortening

Examples: deltoid,

biceps brachii



Soleus

Higher percentage of

slow twitch red fibers

Relatively slow torespond

Tend to shorten &increase in tensionwhen under strain

Examples are erectorspinae, transverse

abdominus & soleus.



Distribution is intermingled & geneticallydetermined. Some people have a large amount of slow

twitch fibers & their muscles tend to be long& lean which predisposes them for longduration activities such as marathons ordistance biking.

Others have large amounts of fast twitchfibers & their muscles tend to be larger &thicker making them great sprinters or bodybuilders



Small motor units are composed of red slowtwitch fibers

Large motor units are composed of white fasttwitch fibers

Motor units are homogenous in that a motorunit either has all red slow twitch or all whitefast twitch fibers



Types of Muscle Contraction





Occur when tension is generated in a musclebut the joint angle & muscle length don’t

change

This type of contraction is used to stabilize

joints Pushing or pulling against an immoveable

object or holding an object in a fixed positionrequires effort by the muscles but no motion

in the joints.



Muscle contractions that change the length

of the muscle and create movement

2 Types:

◦Concentric: in this type of muscle

contraction, the muscle shortens & jointangle decreases.

◦Eccentric: in this type of muscle

contraction, the muscle lengthens & jointangle increases.





Used to slow & control movements Occurs when the muscle lengthens while under

tension & changes in tension happen to controlthe downward movement of load

The eccentrically contracting muscles can

generate an upward force when we need to resistthe pull of gravity.

Eccentric contractions are the most powerful,

followed by isometric, then concentric.

Eccentric contractions are about 50% moreforceful than concentric but use less oxygen &energy & involve fewer muscle fibers.



Results in

lengthening of the

active muscle (one

doing the ‘negative

work’) such as the

controlled down-

phase of biceps curl

Sit-ups, deep knee

bends squats are

eccentric

contractions of the

hamstrings



Injuries often occur with eccentriccontractions when we try to prevent orcontrol movements such as falling ordropping an object.

Eccentric contractions more often causeDelayed Onset Muscle Soreness (DOMS) 8-24hours after activity.

Why DOMS happens is unclear but it may be

that the action of stretching or lengthening ismore likely to cause microtears in the muscle.



Tonic (Tone):

◦ A continual partial contraction◦ At any one moment a small number of the total

fibers in a muscle contract, producing tautness ofthe muscle rather than a recognizable contraction

& movement

Fibrillation:

◦ An abnormal type of contraction in whichindividual fibers contract asynchronously,producing a flutter of the muscle but no effectivemovement

◦ Fibrillation of the heart occurs fairly often.



Twitch:

◦ Single quick, jerky muscular contraction from asingle nerve impulse followed by relaxation

Tetanic:

◦ A continuous, forceful muscular contractionarising from a series of at least 30 nerve impulsesper second

◦ Also known as a spasm or cramp



Concentric contractions create

movement

Eccentric contractions modify

movement

Isometric contractions:

◦ Stop movement

◦ Act to fix or stabilize body parts or

to prevent an undesired joint

movement



Definitions



Threshold Stimulus All or None Response

Minimal nervousstimulus neededto initiate amuscularcontraction

If a muscle fibercontracts at all, itwill contractcompletely or allthe way



Integrating Contraction Types in

Human Movement



When a jointed area moves intoflexion & the joint angle is decreased:◦ The prime mover synergists areconcentrically contracting.

◦ The antagonist eccentrically contractwhile lengthening

◦ The fixators isometrically contract &

stabilize the attachment at the originof the prime mover



Integrating Contraction Types in Human

Movement



The quadriceps muscles are extending theknee, allowing you to rise from the chair.What type of contraction?

The muscles of your back & trunk are keeping

you steady as you rise.What kind of contraction?

If you decide to sit back down, the quadricepsmuscles slow your descent.

What type of contraction?



Quadriceps are in a concentric contraction.

These are isometric contractions of your back& trunk muscles.

The quadriceps are in an eccentric

contraction. These contractions keep youfrom flopping down into the chair.



Standing at a sink holding a pot in one hand &filling it with water from the tap. What type of

contraction for elbow flexor muscles?

Once the pot is full, you lift it up & away from the

faucet.What type of contraction for those same elbow

flexors?

You carry the pot to the stove & carefully lower it

to the burner trying not to spill the water or dropthe pot. What kind of contraction? Which

muscles? What are the opposing muscles doing?



You feel the muscles on the front of yourupper arm (elbow flexors) working harder asthe pot fills. This is an isometric contractionto hold the pot steady.

Lifting the pot is a concentric contraction ofthe elbow flexors.

Eccentric contractions of the elbow flexors

control the lowering of the pot onto the

burner. The elbow extensors are in aconcentric contraction.





Brachialis

Cross & act on onlyone joint

Example: Brachialis



Cross act directly

on two joints

Common in the

body

Examples include

Hamstrings, Biceps

Brachii,

Gastrocnemius



Act on 3 or more

joints due to the line

of pull between their

origin their

insertion crossing

multiple joints

Examples are

muscles that move

the fingers toes

such as flexor

digitorum profundus





As a muscle shortens, its ability to exert forcediminishes.

Active insufficiency: when a muscle shortensto the point where it can’t generate or

maintain active tension Passive insufficiency: when the opposing

muscle is stretched to the point it can nolonger lengthen & allow movement

These principles are most easily observed inbiarticular & multiarticular muscles.



A good example is seen in wrist movements.◦ For active insufficiency, making a fist with the

wrist extended is easier than doing it with thewrist flexed.

◦ The shortened flexor muscles are weaker as they

attempt to make a fist.◦ In the multiarticular muscles of the extensors of

the wrist & fingers, passive insufficiency limitsfinger & wrist flexion when they are performedtogether.

◦ A greater range of motion of wrist flexion ispossible with the fingers extended.



Muscle Relationships or Roles



Involved in creating a joint movement or desired action.

Also called a prime mover if it is the most powerfulmover.

Prime movers are primarily responsible for moving a joint through a given action such as flexion orabduction.

For example, the deltoid is primarily responsible forshoulder abduction so it is the agonist & prime moverfor this movement.

A group of movers or agonists can exist for a specificaction but it does not mean that every muscle of thatgroup contracts every time the action occurs.

It is possible for one or a few muscles in the group tocontract & produce the movement while the rest of themuscles of the group are relaxed.



Muscles also have roles by their muscleactions: flexors, extensors, abductors,adductors, rotators, supinator, pronators,dorsiflexors & plantar flexors.

No matter the role they play, muscles stillrespond to the requirements of thresholdstimulus & all-or-none response.

Flexors, internal rotators, & adductors are

about 25%-30% stronger than theirantagonists.



Usually located on the opposite side of the jointfrom the agonist

Perform opposite actions to the agonist

Example: Latissimus dorsi performs shoulderadduction so it is an antagonist to the deltoid

supraspinatus.

Opposite actions include:

◦ Flexion & extension

◦ Abduction & adduction

◦ Internal & external rotation

Antagonist to biceps in supination - pronator teres



The agonist-antagonist relationship is criticalfor balanced posture as well as for slowing &controlling movements.

For example, the erector spinae (trunk

extensors) are counterbalanced by theantagonist rectus abdominus (trunk flexor).

Proper development of each is critical formaintaining normal, upright trunk posture.



In walking, the hip flexors & knee extensorsswing the leg anteriorly thereby helping topropel the body forward.

The hip extensors & knee flexors are required

to slow & stop this movement. Without proper balance between these muscle

groups, the body would not be able to control& finish movements it initiates.



General Rules:

◦ With upward movements, agonists work &antagonists relax

◦ With horizontal movements, agonists work

& antagonists relax◦ With downward movements, antagonists

work & agonists relax

◦ With faster downward movements,agonists contract & antagonists relax



Biceps in elbow flexion

Deltoids in shoulder abduction

Quadriceps in knee extension

Sternocleidomastoid in neck flexion

Rectus abdominus in bowing

Pectoralis minor in shoulder protraction

Gastrocnemius in plantar flexion

Gluteus medius in abduction

Iliopsoas in hip flexion

Biceps brachii in supination

Serratus anterior in shoulder protraction

Infraspinatus in laterally rotating humerus





Supraspinatus

Assist the function of the

agonist. Muscles that have the

same action or actionsare consideredsynergists.

For example,supraspinatus assists the

deltoid in shoulderabduction which makesthis pair of muscles

synergists.





Latissimus dorsi in shoulder extension Infraspinatus,

Teres minor, major

Triceps in elbow extension Anconeus

Gluteus medius in hip abduction TFL

Gluteus maximus in hip extension Hamstrings

Latissimus dorsi in medial rotation Subscapularis

Teres major

Biceps brachii in supination Supinator

Iliopsoas in hip flexion Rectus femoris

Hamstrings in knee flexion Popliteus

Gastrocnemius

Serratus Anterior in protraction Pectoralis minor

Trapezius in shoulder elevation Levator scapulae

A muscle or a force that can stop an unwanted action at



A muscle or a force that can stop an unwanted action atthe fixed (‘origin’) attachment of the muscle that is

working When a fixator muscle contracts, it contracts isometrically Example: When the levator scapulae contracts, it can

create a pulling force on the cervical vertebrae & thescapula.

If the right levator scapulae is causing right lateral neck

flexion, the fixed attachment is the scapula & the movingattachment is the cervical vertebra.

Its action on the scapula has been cancelled out by thelower trapezius which is creating a downward force on thescapula.

The lower trapezius is performing an isometriccontraction that ‘fixes’ the scapula in place.



Trunk stabilizers

◦ Internal obliques & transverse abdominus

◦ Multifidus◦ Quadratus lumborum

Shoulder stabilizers

◦ Trapezius & levator scapulae◦

Rhomboids◦ Serratus anterior & pectoralis minor

Pelvic stabilizers

◦ External rotators◦ Hip abductors: gluteus medius & minimus, TFL◦ Pelvic floor muscles & diaphragm per some

sources

A muscle or a force that can stop (by an isometric



A muscle or a force that can stop (by an isometriccontraction) an unwanted action at the moving(‘insertion’) attachment of the muscle that is working

Example: When the levator scapulae contracts, it cancreate a pulling force on the cervical vertebrae &scapula.

If the right levator scapulae is contracting & causing theneck to right laterally flex, extend & rotate to the right,

the fixed attachment is the scapula & the movingattachment is the cervical vertebra. If we only want to laterally flex to the right & not extend

or rotate to the right, then the other 2 actions must bestopped.

SCM contracting as a neutralizer stops both undesired

actions. SCM creates a flexion force that cancels out the

extension & a left rotation of the neck that cancels outthe right rotation.

A muscle that can hold another part of the body (by an



A muscle that can hold another part of the body (by anisometric contraction) in position while the joint action

is occurring Does not work directly at the site of the joint action &

often works far from where the action is occurring

Usually works against gravity

Creates a contraction force that is equal in strength but

opposite in direction to the force gravity exerts on thatbody part

The body part does not fall & the support muscle doesnot contract so hard that the body part is movedupward

Example: When holding a barbell in the right hand &doing bicep curls, the left erector spinae prevents thetorso from laterally flexing toward the weight on theright side of the body



Myotomes: Group of muscles innervated by

the motor fibers of a single spinal nerve root

Dermatomes: Skin area innervated by thesensory fibers of a single spinal nerve root

While slight variations exist, dermatome &myotome distribution patterns are relativelyconsistent between individuals





Myotome = orange

Dermatomes = blue



C3, 4 & 5 supply the diaphragm C5 also supplies the shoulder muscles & biceps C6 is for wrist extensors C7 is for elbow extensors C8 is for finger flexors T1 is for finger abduction

T1–T12 supplies the chest wall & abdominal muscles L2 flexes the hip L3 extends the knee L4 dorsiflexes the foot L5 wiggles the toes

S1 plantar flexes the foot S3, 4 & 5 supply the bladder, bowel & sex organs & the

anal & other pelvic muscles



In diagrams or maps, the boundaries ofdermatomes are usually sharply defined

However, in life there is considerable overlapof innervation between adjacent dermatomes.

If there is a loss of sensory nerve function byone spinal nerve, sensation from the regionof skin it supplies is not usually completelylost

The skin areas served by spinal nerves have

some overlap but there will be a reducedsensitivity if one spinal nerve is damaged



Common Injuries



Salvo p. 148

Results from

overstretching muscletissue, usually themuscle is overloadedwith the severity of theinjury related to theamount & rate of

overloading. Strains can be mild,

moderate & severe Rated as first degree,

second degree & thirddegree.



Caused by compressive

forces sustained during

impact result in

hematomas or bruises in

the muscle tissue.

Caution is indicated in

massaging over

contusions

Force depth of

pressure need to be

reduced to prevent

further injury.

Lymphatic drainage

applications are usually

appropriate.



Myositis Ossificans Cramps

A possible complication of

a serious contusion The theory is that fibro-

blasts recruited duringhealing process begin tobecome osteoblasts &

produce a calcified masswithin the muscle tissue.

The mass is usuallyreabsorbed by the bodyover time.

Causes can include

electrolyte imbalance,deficiencies in calciumand magnesium, &dehydration.

Cramps may involvemoderate to severemuscle spasms withproportional levels ofpain.



Muscle soreness that occurs after unaccustomed

exercise.

Characterized by pain, swelling, stiffness restricted

movement.

Symptoms appear 24 - 48 (or 72) hours after activity.

Causes can include microtears or microtrauma tomuscle tissue which stimulates inflammatory response

Associated more with eccentric & isometriccontractions.

Other causes can include damage to the connectivetissue that holds the muscle together & increasedinterstitial fluid in the area

Can be treated by applications of ice for the first 48-72hrs & by massage with emphasis on lymphatic drainage.



Bleeding or edema within a musclecompartment from injury or excessivemuscular exertion.

Pressure increases within the compartmentwhich can severely damage nerves & blood

vessels. Symptoms: swelling, discoloration,

diminished distal pulse, loss of sensation,tingling, & loss of motor function.

The individual needs to be referred to aphysician



Tendonitis

Inflammation of atendon caused byfrequentmicrotrauma with

symptoms ofswelling & pain



SCM in neck flexion

Biceps in elbow flexion

Quadriceps in knee

extension

Deltoids in shoulder

abduction

Serratus Anterior in

shoulder protraction


Serratus Anterior in

shoulder protraction

Trapezius in shoulder

elevation

Gluteus maximus in

hip extension


Latissimus in shoulder

extension

Latissimus in medial

rotation

Documents

K Class 5 TG2 Muscular System Review