Post on 19-Dec-2015
Muscular System Muscular System FunctionsFunctions
Body movementBody movement Maintenance of postureMaintenance of posture RespirationRespiration Production of body heatProduction of body heat CommunicationCommunication Constriction of organs and vesselsConstriction of organs and vessels Heart beatHeart beat
Properties of MuscleProperties of Muscle
ContractilityContractility Ability of a muscle to shorten with forceAbility of a muscle to shorten with force
ExcitabilityExcitability Capacity of muscle to respond to a stimulusCapacity of muscle to respond to a stimulus
ExtensibilityExtensibility Muscle can be stretched to its normal resting Muscle can be stretched to its normal resting
length and beyond to a limited degreelength and beyond to a limited degree ElasticityElasticity
Ability of muscle to recoil to original resting Ability of muscle to recoil to original resting length after stretchedlength after stretched
Muscle Tissue TypesMuscle Tissue Types SkeletalSkeletal
Attached to bonesAttached to bones Nuclei multiple and peripherally locatedNuclei multiple and peripherally located Striated, Voluntary and involuntary (reflexes)Striated, Voluntary and involuntary (reflexes)
SmoothSmooth Walls of hollow organs, blood vessels, eye, Walls of hollow organs, blood vessels, eye,
glands, skinglands, skin Single nucleus centrally locatedSingle nucleus centrally located Not striated, involuntary, gap junctions in Not striated, involuntary, gap junctions in
visceral smoothvisceral smooth CardiacCardiac
HeartHeart Single nucleus centrally locatedSingle nucleus centrally located Striations, involuntary, intercalated disksStriations, involuntary, intercalated disks
Skeletal Muscle Skeletal Muscle StructureStructure
Muscle Muscle fibersfibers or or cellscells Develop from Develop from
myoblastsmyoblasts Numbers remain Numbers remain
constantconstant Connective tissueConnective tissue Nerve and blood Nerve and blood
vesselsvessels
Connective Tissue, Nerve, Connective Tissue, Nerve,
Blood VesselsBlood Vessels Connective tissueConnective tissue
External laminaExternal lamina EndomysiumEndomysium PerimysiumPerimysium FasciculusFasciculus EpimysiumEpimysium
FasciaFascia Nerve and blood Nerve and blood
vesselsvessels AbundantAbundant
Sliding Filament Model Sliding Filament Model I:I:
Actin myofilaments Actin myofilaments sliding sliding over over myosin to shorten sarcomeresmyosin to shorten sarcomeres Actin and myosin do not change lengthActin and myosin do not change length Shortening sarcomeres responsible for Shortening sarcomeres responsible for
skeletal muscle contractionskeletal muscle contraction During relaxation, sarcomeres During relaxation, sarcomeres
lengthenlengthen
Physiology of Skeletal Physiology of Skeletal MuscleMuscle
Nervous systemNervous system Controls muscle Controls muscle
contractions through contractions through action potentialsaction potentials
Resting Resting membranemembrane potentialspotentials Membrane voltage Membrane voltage
difference across difference across membranes membranes (polarized)(polarized)
• Inside cell more Inside cell more negative and more Knegative and more K++
Outside cell more Outside cell more positive and more Napositive and more Na++
Must exist for action Must exist for action potential to occurpotential to occur
Action PotentialsAction Potentials PhasesPhases
DepolarizationDepolarization Inside plasma Inside plasma
membrane becomes membrane becomes less negativeless negative
RepolarizationRepolarization Return of resting Return of resting
membrane potentialmembrane potential All-or-none principleAll-or-none principle
Like camera flash Like camera flash systemsystem
PropagatePropagate Spread from one Spread from one
location to anotherlocation to another FrequencyFrequency
Number of action Number of action potential produced per potential produced per unit of timeunit of time
Excitation-Contraction Excitation-Contraction CouplingCoupling
Mechanism where an Mechanism where an action potential action potential causes muscle fiber causes muscle fiber contractioncontraction
InvolvesInvolves SarcolemmaSarcolemma Transverse or T tubulesTransverse or T tubules Terminal cisternaeTerminal cisternae Sarcoplasmic reticulumSarcoplasmic reticulum CaCa2+2+
TroponinTroponin
Muscle TwitchMuscle Twitch
Muscle contraction Muscle contraction in response to a in response to a stimulus that stimulus that causes action causes action potential in potential in one or one or moremore muscle fibers muscle fibers
PhasesPhases Lag or latentLag or latent ContractionContraction RelaxationRelaxation
Stimulus Strength and Stimulus Strength and Muscle ContractionMuscle Contraction
All-or-none law for All-or-none law for muscle fibersmuscle fibers Contraction of equal force Contraction of equal force
in response to each action in response to each action potentialpotential
Sub-threshold stimulusSub-threshold stimulus Threshold stimulusThreshold stimulus Stronger than thresholdStronger than threshold
Motor unitsMotor units Single motor neuron and all Single motor neuron and all
muscle fibers innervatedmuscle fibers innervated Graded for whole musclesGraded for whole muscles
Strength of contractions Strength of contractions range from weak to strong range from weak to strong depending on stimulus depending on stimulus strengthstrength
Types of Muscle Types of Muscle ContractionsContractions
IsometricIsometric: No change in length but : No change in length but tension increasestension increases Postural muscles of bodyPostural muscles of body
IsotonicIsotonic: Change in length but tension : Change in length but tension constantconstant ConcentricConcentric: Overcomes opposing resistance : Overcomes opposing resistance
and muscle shortensand muscle shortens EccentricEccentric: Tension maintained but muscle : Tension maintained but muscle
lengthenslengthens Muscle toneMuscle tone: Constant tension by : Constant tension by
muscles for long periods of timemuscles for long periods of time
Multiple Motor Unit Multiple Motor Unit SummationSummation
A whole muscle contracts with a small or A whole muscle contracts with a small or large force depending on number of large force depending on number of motor units stimulated to contractmotor units stimulated to contract
Multiple-Wave Multiple-Wave SummationSummation
As frequency of action As frequency of action potentials increase, potentials increase, frequency of contraction frequency of contraction increasesincreases
Action potentials come Action potentials come close enough together so close enough together so that the muscle does not that the muscle does not have time to completely have time to completely relax between relax between contractions.contractions.
TetanusTetanus Incomplete tetanusIncomplete tetanus
Muscle fibers Muscle fibers partially relax partially relax between contractionbetween contraction
There is time for Ca There is time for Ca 2+2+ to be recycled to be recycled through the SR through the SR between action between action potentialspotentials
TetanusTetanus Complete tetanusComplete tetanus
No relaxation No relaxation between between contractionscontractions
Action potentials Action potentials come sp close come sp close together that Ca together that Ca 2+2+ does not get re-does not get re-sequestered in the sequestered in the SRSR
TreppeTreppe
Graded responseGraded response Occurs in muscle Occurs in muscle
rested for rested for prolonged periodprolonged period
Each subsequent Each subsequent contraction is contraction is stronger than stronger than previous until all previous until all equal after few equal after few stimuli stimuli
Energy SourcesEnergy Sources
ATP provides immediate energy for ATP provides immediate energy for muscle contractions from muscle contractions from 3 sources3 sources Creatine phosphateCreatine phosphate
During resting conditions stores energy to During resting conditions stores energy to synthesize ATPsynthesize ATP
Anaerobic respirationAnaerobic respiration Occurs in absence of oxygen and results in Occurs in absence of oxygen and results in
breakdown of glucose to yield breakdown of glucose to yield ATPATP and lactic acid and lactic acid Aerobic respirationAerobic respiration
Requires oxygen and breaks down glucose to Requires oxygen and breaks down glucose to produce produce ATPATP, carbon dioxide and water, carbon dioxide and water
More efficient than anaerobicMore efficient than anaerobic
Slow and Fast FibersSlow and Fast Fibers Slow-twitch or Slow-twitch or high-oxidativehigh-oxidative
Contract more slowly, smaller in diameter, Contract more slowly, smaller in diameter, better blood supply, more mitochondria, more better blood supply, more mitochondria, more fatigue-resistant than fast-twitch fatigue-resistant than fast-twitch
Fast-twitch or Fast-twitch or low-oxidativelow-oxidative Respond rapidly to nervous stimulation, contain Respond rapidly to nervous stimulation, contain
myosin to break down ATP more rapidly, less myosin to break down ATP more rapidly, less blood supply, fewer and smaller mitochondria blood supply, fewer and smaller mitochondria than slow-twitchthan slow-twitch
Distribution of Distribution of fast-twitch and slow twitchfast-twitch and slow twitch Most muscles have both but varies for each Most muscles have both but varies for each
musclemuscle Effects of exerciseEffects of exercise
HypertrophiesHypertrophies: Increases in muscle size: Increases in muscle size AtrophiesAtrophies: Decreases in muscle size: Decreases in muscle size
FatigueFatigue Decreased capacity to work and Decreased capacity to work and
reduced efficiency of performancereduced efficiency of performance Types:Types:
PsychologicalPsychological Depends on Depends on emotional stateemotional state of individual of individual
MuscularMuscular Results from Results from ATPATP depletion depletion
SynapticSynaptic Occurs in neuromuscular junction due to Occurs in neuromuscular junction due to
lack of acetylcholine lack of acetylcholine
Effects of Aging on Effects of Aging on Skeletal MuscleSkeletal Muscle
Reduced Reduced muscle massmuscle mass Increased time for muscle to contract Increased time for muscle to contract
in in responseresponse to nervous stimuli to nervous stimuli Reduced Reduced staminastamina Increased Increased recovery timerecovery time Loss of Loss of muscle fibersmuscle fibers Decreased density of Decreased density of capillariescapillaries in in
musclemuscle