WALK ALONG THEORYWALK ALONG THEORYChemical events, Muscle twitch, Chemical events, Muscle twitch,

Muscle tone, Muscle spasmMuscle tone, Muscle spasm

INHIBITION OF ACTIN FILAMENT BY THE INHIBITION OF ACTIN FILAMENT BY THE TRPONIN-TROPOMYOSIN COMPLEXTRPONIN-TROPOMYOSIN COMPLEX

ACTIN FILAMENT 1ACTIN FILAMENT 1Absence of troponin-Absence of troponin-tropomyosin complextropomyosin complexPresence of magnesium Presence of magnesium ions and ATPions and ATPAttachment of heads with Attachment of heads with binding sites on actin binding sites on actin filamentfilament

ACTIN FILAMENT 2ACTIN FILAMENT 2Presence of troponin-Presence of troponin-tropomyosin complextropomyosin complex

No attachment of heads No attachment of heads with binding sites on actin with binding sites on actin filamentfilamentConsequently binding Consequently binding sites are covered in sites are covered in relaxed musclerelaxed muscle

ROLE OF CALCIUM IONSROLE OF CALCIUM IONS

In the presence of large amount of calcium In the presence of large amount of calcium ionsionsInhibitory effect of calcium ions on Inhibitory effect of calcium ions on troponin-tropomyosin complex can be troponin-tropomyosin complex can be inhibitedinhibitedBinding of calciom ions with troponin CBinding of calciom ions with troponin CContraction initiatesContraction initiates

Role of calcium ionsRole of calcium ions

Each molecule can bind upto four calcium Each molecule can bind upto four calcium ionsionsConformational changeConformational changeMoves deeper into the grooves between Moves deeper into the grooves between two actin strandstwo actin strandsUncovers sitesUncovers sitesAllowance the cross bridges for Allowance the cross bridges for attachmentattachment

Role of calcium ion Conti----Role of calcium ion Conti----

Initiation of contractionInitiation of contraction

THE WALK ALONG THEORYTHE WALK ALONG THEORYRatchet theory of contractionRatchet theory of contractionAttachment of head to active siteAttachment of head to active siteChanges in intramolecular forces between head and armChanges in intramolecular forces between head and armTilting of headTilting of headPower strokePower strokeDrag the actin filamentDrag the actin filamentHead automatically breaksHead automatically breaksRecovery strokeRecovery strokeHead of the bridge walk along the actin filamentHead of the bridge walk along the actin filamentEngaging and disengaging repeatedlyEngaging and disengaging repeatedly

WALK ALONG THEORYWALK ALONG THEORY

Chemical events in the motion of Chemical events in the motion of myosin headsmyosin heads

Muscle contractionMuscle contractionWork performedWork performedATP cleavageATP cleavageFenn effectFenn effect

Chemical events in the motion of Chemical events in the motion of myosin headsmyosin heads

Steps before contractionSteps before contraction Binding of ATP with myosin headBinding of ATP with myosin head ATPase activityATPase activity Conformation of head is perpendicularConformation of head is perpendicular Binding of Sub-unit of tropomyosin- troponin Binding of Sub-unit of tropomyosin- troponin

complex with Ca ionscomplex with Ca ions Uncovering the sitesUncovering the sites Bond between head and active site causes Bond between head and active site causes

tilting of headtilting of head

Chemical events in the motion of Chemical events in the motion of myosin headsmyosin heads

Power strokePower strokeStorage of energy like a cocked stringStorage of energy like a cocked stringCleavage products act as source of Cleavage products act as source of

energyenergyRelease of ADPRelease of ADPBinding of new ATP moleculeBinding of new ATP moleculeRepeats the cycleRepeats the cycle

MYOSIN HEADMYOSIN HEAD

ATPase activityATPase activityEssential for muscle contractionEssential for muscle contraction

MUSCLE TWITCHMUSCLE TWITCH

It is small, local involuntary muscle It is small, local involuntary muscle contraction visible under the skin contraction visible under the skin representing spontaneous discharge of representing spontaneous discharge of fibers innervated by single motor nervefibers innervated by single motor nerveCauseCauseIt is caused by minor muscle contractions It is caused by minor muscle contractions in the area or uncontrollable twitching of in the area or uncontrollable twitching of muscle group that is served by single muscle group that is served by single motor nerve fibermotor nerve fiber

MUSCLE SPASMMUSCLE SPASM

Persistant increased tension and Persistant increased tension and shortness in a muscle that cannot be shortness in a muscle that cannot be released voluntarilyreleased voluntarily

Abnormal and painful contraction of Abnormal and painful contraction of muscle fibersmuscle fibers

MUSCLE SPASMMUSCLE SPASM

CauseCauseIt is caused by pain stimuli to lower motor It is caused by pain stimuli to lower motor neuronsneurons

Sudden caused by overuse or Sudden caused by overuse or overstimulationoverstimulation

ISOMETRIC CONTRACTIONISOMETRIC CONTRACTION

It is contraction of muscle without It is contraction of muscle without changing the length of musclechanging the length of muscleMuscle tries to contract but cannotMuscle tries to contract but cannotWorking of heart indirectlyWorking of heart indirectlyExampleExampleTried to lift an immovable objectTried to lift an immovable object

ISOTONIC CONTRACTIONISOTONIC CONTRACTIONIt is contraction of muscle with changing the It is contraction of muscle with changing the length of musclelength of muscleTonic refers to tension Tonic refers to tension Muscle shortening ,the attached body part movesMuscle shortening ,the attached body part movesBurning of caloriesBurning of caloriesExamplesExamplesSwinging a ballSwinging a ballThrowing a ballThrowing a ballLifting a weightLifting a weight

Fast versus slow muscle fibersFast versus slow muscle fibersFast muscle fibersFast muscle fibersLarger fiberLarger fiberRapid contractionRapid contractionRespond quicklyRespond quicklyGreat strength of contractionGreat strength of contractionExtensive sarcoplasmic Extensive sarcoplasmic reticulumreticulumCategorized into 2 types.Categorized into 2 types.Type 1Type 1Type 2Type 250% fibers in human muscles50% fibers in human muscles

Slow muscle fibersSlow muscle fibersSmaller fibersSmaller fibersSlow contractionSlow contractionRespond not spontaneouslyRespond not spontaneouslyProlonged contractionProlonged contractionLess extensive sarcoplasmic Less extensive sarcoplasmic reticulumreticulum

50% fibers in human muscles50% fibers in human muscles

Fast versus slow muscle fibersFast versus slow muscle fibersFast muscle fibersFast muscle fibersLarge amount of Large amount of glycolytic enzymesglycolytic enzymesLess extensive blood Less extensive blood supplysupplyLess mitochondriaLess mitochondria

White muscle fibersWhite muscle fibersDeficit of myoglobinDeficit of myoglobinExampleExampleOlypmic sprinterOlypmic sprinter

Slow muscle fibersSlow muscle fibersLess amount of glycolytic Less amount of glycolytic enzymesenzymesExtensive blood supplyExtensive blood supplyLarge number of Large number of mitochondriamitochondriaRed muscle fibersRed muscle fibersPresence of myoglobinPresence of myoglobin

ExampleExampleOlympic long distance Olympic long distance runnersrunners

Characteristics of isometric contraction Characteristics of isometric contraction from different stimulifrom different stimuli

MuscleMuscless

Ocular muscleOcular muscleGatroneimus muscleGatroneimus muscleSoleus muscleSoleus muscle

Duration of isometric Duration of isometric cotractioncotraction

<1/40 sec<1/40 sec1/15 sec1/15 sec1/3 sec1/3 sec

MOTOR UNITMOTOR UNIT

Motor unit leave spinal cordMotor unit leave spinal cordEntrance of nerves into Entrance of nerves into musclemuscleSmall muscles react rapidlySmall muscles react rapidlyRequirement of fine controlRequirement of fine controlMore nerve fibers/muscle More nerve fibers/muscle fibersfibersExample: laryngeal musclesExample: laryngeal muscles80-100 muscle fibers/motor 80-100 muscle fibers/motor unitunitQuick excitableQuick excitableFibers are not in bunched Fibers are not in bunched formformFormation of microbundlesFormation of microbundles

Force summationForce summationAdding together of individual twitch Adding together of individual twitch contractioncontraction

Multiple fiber summationMultiple fiber summationIncreasing number of motor unitsIncreasing number of motor units

Frequency summationFrequency summationIncreasing frequencyIncreasing frequency

Multiple fiber summationMultiple fiber summationSize principleSize principle CNS sends weak signal to muscleCNS sends weak signal to muscleMotor unitsMotor unitsContraction of smaller motor unitsContraction of smaller motor unitsIntensity of signal increasesIntensity of signal increasesContraction of larger motor unitsContraction of larger motor units

CauseCauseDriven by small motor nerve fibers Driven by small motor nerve fibers AsynchronizationAsynchronization

FREQUENCY SUMMATIONFREQUENCY SUMMATION

TETANIZATIONTETANIZATION

A state of continuous A state of continuous muscle contraction muscle contraction without periods of without periods of relaxationrelaxationOccurrence of series Occurrence of series of rapid nerve of rapid nerve impulsesimpulses

Frequency summationFrequency summation Heart cannot be tetanized due to its electrical Heart cannot be tetanized due to its electrical

propertiesproperties

Inactivity of Ca pumpInactivity of Ca pumpEnough Ca ions are maintained in sarcoplasmEnough Ca ions are maintained in sarcoplasm

Maximum strength of muscle contraction at a Maximum strength of muscle contraction at a normal muscle length is between 3 and 4kgnormal muscle length is between 3 and 4kg