muscles the muscular system functions body movement maintenance of position respiration / organ...
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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.
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