MusclesMuscles

The Muscular System The Muscular System FunctionsFunctions

Body MovementBody Movement

Maintenance of PositionMaintenance of Position

Respiration / organ volumeRespiration / organ volume

Production of Body Heat Production of Body Heat (Thermogensis)(Thermogensis)

Movement of substances Movement of substances (construction of organ and (construction of organ and vessels)vessels)

Heart BeatHeart Beat

Characteristics of Skeletal MuscleCharacteristics of Skeletal Muscle

Contractility A muscle’s ability to shorten and generate force to do

useful work at the expense of cellular energy. Excitability

Muscles need to be stimulated before contracting Extensibility

The way muscles can be stretched without damage Elasticity

Muscle’s return to their original length and shape after contracting

Conductivity – conducts action / potential along plasma membrane

Skeletal muscle pictureSkeletal muscle picture

Striated, multinucleated and voluntaryStriated, multinucleated and voluntary

Skeletal MuscleSkeletal Muscle

Each skeletal muscle fiber is a single cell Each skeletal muscle fiber is a single cell containing numerous myofibrilscontaining numerous myofibrils

Myofibrils are composed of actin and myosin Myofibrils are composed of actin and myosin myofilaments myofilaments

Myofibrils are joined end to end to form Myofibrils are joined end to end to form sarcomeressarcomeres

Muscle fibers are organized into fasciculi and Muscle fibers are organized into fasciculi and fasciculi are organized into muscles by fasciculi are organized into muscles by associated connected tissue.associated connected tissue.

MyofilamentsSacomere

Myofibrils

Connective tissue componentsConnective tissue components

Endomysium – separating individual Endomysium – separating individual muscle fibersmuscle fibers

Perimysium – surround borders of 10 – Perimysium – surround borders of 10 – 100 fibers (fascicles)100 fibers (fascicles)

Epimysium – outlines the whole muscleEpimysium – outlines the whole muscle Deep fascia – dense irregular tissue, holds Deep fascia – dense irregular tissue, holds

muscles together, separating into muscles together, separating into functional groups.functional groups.

Smooth MusclesSmooth Muscles

Smooth muscle is nonstriated Smooth muscle is nonstriated (striped), uninucleated, and (striped), uninucleated, and involuntary. Visceral organs involuntary. Visceral organs (alimentary canal)(alimentary canal)

Cardiac MuscleCardiac Muscle

**Cardiac: striated, uninucleated, branches, Cardiac: striated, uninucleated, branches, interculated discs, involuntaryinterculated discs, involuntary

Both Cardiac and Smooth muscle are under Both Cardiac and Smooth muscle are under involuntary control and is influenced by involuntary control and is influenced by hormones, such as epinephrine.hormones, such as epinephrine.

Innervation of a Motor Unit and Innervation of a Motor Unit and Muscle FiberMuscle Fiber

This neuron motors more than one muscle fiber.

There may be 500 to

1,000 muscle fibers per neuron

Muscle fiber is innervated

by one single motor neuron

Neuroelectrical factorsNeuroelectrical factors

Potassium ions (K+) are greater inside the Potassium ions (K+) are greater inside the muscle cell than outside, whereas sodium ions muscle cell than outside, whereas sodium ions (Na+) are greater outside than inside(Na+) are greater outside than inside

The inside of cell is negatively charged The inside of cell is negatively charged electrically, whereas outside is positively electrically, whereas outside is positively chargedcharged

(Neuromuscular junction) Nerve impulse (Neuromuscular junction) Nerve impulse reaching the neuromuscular junction causes and reaching the neuromuscular junction causes and axon ending to release the neurotransmitter axon ending to release the neurotransmitter acetylcholine.acetylcholine.

Neuronelectical factor con’tNeuronelectical factor con’t This makes cell membrane permeable to Na+. This makes cell membrane permeable to Na+.

They rush in creating an electrical potential. K+ They rush in creating an electrical potential. K+ begins to move out to restore resting potential begins to move out to restore resting potential (Not as Na+ comes in)(Not as Na+ comes in)

This causes muscles to generate its own This causes muscles to generate its own impulse called the action potential impulse called the action potential

The sarcoplasm reticulum then release Ca++ The sarcoplasm reticulum then release Ca++ into the fluids surrounding myofibrils.into the fluids surrounding myofibrils.

Ca++ stops the action of the inhibitor substance Ca++ stops the action of the inhibitor substance troponin and tropomysin (which keep actin and troponin and tropomysin (which keep actin and myosin apart), causing contractile process to myosin apart), causing contractile process to occuroccur

Chemical factorsChemical factors Ca++ combines loosely with myosin to form activated Ca++ combines loosely with myosin to form activated

myosin.myosin. Activated myosin reacts with ATP, attached to the Activated myosin reacts with ATP, attached to the

myosin, and releases energy from the ATP to form myosin, and releases energy from the ATP to form actomyosinactomyosin

Myosin filaments have cross bridges that now connect Myosin filaments have cross bridges that now connect with the actin and pull the actin filaments in among the with the actin and pull the actin filaments in among the myosin filamentmyosin filament

A sliding process occurs: The width of the A bands A sliding process occurs: The width of the A bands remain constant, but Z lines move closer. By now the remain constant, but Z lines move closer. By now the sodium – potassium pump has kicked in to restore the sodium – potassium pump has kicked in to restore the resting potential. Ca++ gets reabsorbed and contraction resting potential. Ca++ gets reabsorbed and contraction ceasesceases

Energy sources: ATPEnergy sources: ATP

Glycolysis: glucose to pyruvic acid, net Glycolysis: glucose to pyruvic acid, net gain of 8 ATP if O2 present, if no O2 then gain of 8 ATP if O2 present, if no O2 then lactic acid (burn in muscles) forms with net lactic acid (burn in muscles) forms with net gain of 2 ATPgain of 2 ATP

Krebs’ citric acid cycle: pyruvic to Krebs’ citric acid cycle: pyruvic to CO2+H2O+30 ATP (28 ATP + 2 GTP)CO2+H2O+30 ATP (28 ATP + 2 GTP)

Phosphocreatine in muscle cells: used in Phosphocreatine in muscle cells: used in sprintingsprinting

Free fatty acid: fatty acids + H2O + ATPFree fatty acid: fatty acids + H2O + ATP

Muscle Terms Muscle Terms

TwitchTwitch A sudden uncontrollable muscle spasmA sudden uncontrollable muscle spasm

ThresholdThreshold A very small detectable sensationA very small detectable sensation

All-or-none responseAll-or-none response A muscle will respond to stimulation completely or not A muscle will respond to stimulation completely or not

at allat all Lag phase Lag phase

The interval of time between stimulus and The interval of time between stimulus and contractions contractions

Muscle Terms Muscle Terms (Cont.)(Cont.)

Contraction phaseContraction phase Tension rises to a peakTension rises to a peak

Relaxation phaseRelaxation phase The phase of decreased tension after all or noneThe phase of decreased tension after all or none

TetanusTetanus Calcium ions cause spasmodic / sustained Calcium ions cause spasmodic / sustained

contractionscontractions RecruitmentRecruitment

Patterns and corresponding change of muscle Patterns and corresponding change of muscle patterns, increase number of motor units activatedpatterns, increase number of motor units activated

Muscle Anatomy TermsMuscle Anatomy Terms Tendon

Tough fibers that connect muscle to bony structures; wide flat sheet called aponeurosis

Origin The head of the muscle, where it is located, stationary bone

Head Explains where the muscle begins

Insertion Muscle’s relationship with other muscles, moveable bone

Belly The fleshy part of the contracting muscle Resistance – force opposes movement Effort – force exerted to achieve movement

Anatomy of Skeletal Muscle Anatomy of Skeletal Muscle A single skeletal muscle, such A single skeletal muscle, such

as the as the tricepstriceps muscle, is muscle, is attached at its attached at its originorigin to a large to a large area of bone; in this case, the area of bone; in this case, the humerus. humerus. At its other end, the At its other end, the insertioninsertion, it tapers into a , it tapers into a glistening white glistening white tendontendon which, which, in this case, is attached to the in this case, is attached to the ulnaulna, one of the bones of the , one of the bones of the lower arm.lower arm.

TermsTerms

Prime moverPrime mover Muscle that contracts (pulls) mainly by itselfMuscle that contracts (pulls) mainly by itself

AntagonistAntagonist A muscle that works opposite of another, A muscle that works opposite of another,

relaxing muscle relaxing muscle SynergistsSynergists

Muscles working togetherMuscles working together

REMEMBER: muscles only pullREMEMBER: muscles only pull

Naming skeletal musclesNaming skeletal muscles

A. Direction of muscle fiber to midlineA. Direction of muscle fiber to midline B. Location – structure near muscle is foundB. Location – structure near muscle is found C. Relative SIZE of muscleC. Relative SIZE of muscle D. NUMBER of origins (tendons)D. NUMBER of origins (tendons) E. SHAPE of MusclesE. SHAPE of Muscles F. Origin and insertion sitesF. Origin and insertion sites G. Action – same as in joints. 2 new are G. Action – same as in joints. 2 new are

Sphincter – decrease size of opening, Tensor – Sphincter – decrease size of opening, Tensor – make body more rigidmake body more rigid

Isometric / Isotonic Isometric / Isotonic Muscle ContractionMuscle Contraction

Isotonic contractionsIsotonic contractions Tension on a muscle stays the same but the muscle Tension on a muscle stays the same but the muscle

shortens so things can be lifted, joints movesshortens so things can be lifted, joints moves

Isometric contractionsIsometric contractions This is when the muscle does not shorten when This is when the muscle does not shorten when

contracting. This can happen when pushing on a wall contracting. This can happen when pushing on a wall or something else that will not move.or something else that will not move.

TONETONE This is a constant state of partial contraction This is a constant state of partial contraction

maintained in a musclemaintained in a muscle

Muscle disorderMuscle disorder

Symptoms: Paralysis, weakness, Symptoms: Paralysis, weakness, degeneration or atrophy, pain, spasmsdegeneration or atrophy, pain, spasms

Causes: Muscular tissue, Vascular system Causes: Muscular tissue, Vascular system feeding muscle cells, nervous system feeding muscle cells, nervous system connections, connective tissue connections, connective tissue surrounding cell bundles (fascicles)surrounding cell bundles (fascicles)

Types of disordersTypes of disorders

Fibromyalgia – muscle painFibromyalgia – muscle pain Myasthenia gravis- muscle tiring / weakness, Myasthenia gravis- muscle tiring / weakness,

acetylcholine receptor destructionacetylcholine receptor destruction Muscular dystrophy- inherited, males, muscles Muscular dystrophy- inherited, males, muscles

degenerate degenerate Hernia – myocele – muscle breaks through sheath, Hernia – myocele – muscle breaks through sheath,

Inguinal – bowel through abdominal muscleInguinal – bowel through abdominal muscle Myoclonus – spasm / twitching of muscle, singultus – Myoclonus – spasm / twitching of muscle, singultus –

hiccup (myoclonus of diaphragm)hiccup (myoclonus of diaphragm) Botox – paralyze the muscle that causes wrinkles.Botox – paralyze the muscle that causes wrinkles.