Term
n1) Skeletal
n2) Cardiac
n3) Smooth
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Definition
| Three Types of Muscle Tissue |
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Term
Producing body movements qWalking, running, holding a pencil qResult from skeletalmuscle contractions pulling on tendons and moving bones of skeleton.
n2) Maintain posture and body position qSkeletal muscle contractions stabilize joints and maintain body posture, e.g. standing, sitting qSustained contractions (tension) of neck muscles hold head upright
n3) Support soft tissues qLayers of skeletal muscle in abdominal wall and pelvic cavity support weight of organs and shield from injury |
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Definition
| Key Functions of Muscle Tissue |
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Term
n4) Guard entrances and exits qSkeletal muscles encircle openings of digestive and urinary tracts qAllow voluntary control over urination, defecation, and swallowing
n5) Generating heat qMuscle tissue is body’s largest source of heat! qUsed to maintain normal body temperature qShivering (involuntary contraction of skeletal muscle) increases heat production
n6) Store nutrient reserves qWhen diet too low in calories, contractile proteins in muscle tissue are broken down, and amino acids used by liver to synthesize glucose for energy. |
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Definition
| Key Functions of Muscle Tissue Cont |
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Term
n7) Moving substances within body
qCardiac muscle contractions of heart pump blood through blood vessels of body qSmooth muscle contractions move fluids and solids through GI tract qSmooth muscle regulates diameters of small arteries qSkeletal muscle contractions promote flow of lymph fluid and help return blood back to heart |
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Definition
| Key Functions of Muscular Tissue Cont |
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Term
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Definition
moves bones, nis striated:
qAlternating light and dark protein bands (striations) are seen when examined with a microscope, nworks mainly in a voluntarymanner
qIts activity can be consciously controlled by neurons, nalso are controlled subconsciously to some extent
qThe diaphragm alternately contracts and relaxes without conscious control so you don’t stop breathing |
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Term
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Definition
nis a separate organ composed of hundred to thousands of cells called muscle fibers.
qMuscle fiber = muscle cell |
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Term
qMuscle tissue
qConnective tissue
qNervous Tissue |
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Definition
| Skeletal muscle composed of |
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Term
| Skeletal Muscle Connective Tissue Components |
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Definition
nSubcutaneous layer or hypodermis and Fascia |
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Term
nSubcutaneous layer or hypodermis |
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Definition
qSeparates muscle from skin
nContains areolar connective and adipose tissues
qProvides pathway for nerves, blood and lymphatic vessels to enter and exit muscles
qAdipose tissue serves as insulating layer and protects muscles from physical trauma |
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Term
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Definition
qDense irregular connective tissue that holds muscles with similar functions together
qAllows free movement of muscles, carries nerves, blood and lymphatic vessels, and fills spaces between muscles |
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Term
| Epimysium, Perimysium, Endomysium |
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Definition
Three layers of connective tissue extend from fascia to protect and strengthen skeletal muscles |
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Term
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Definition
qseparates individual muscle fibers from one another
nContains capillaries, nerve fibers, and myosatellite cells |
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Term
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Definition
surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called qfascicles
nContains blood vessels and nerves
nGives meat its characteristic “grain”; when you tear meat it rips apart along the fascicles |
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Definition
| outermost layer that encircles entire muscle; separates muscles from nearby tissues and organs |
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Term
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Definition
| a rope-like cord of dense regular connective tissue (composed of parallel collagen fibers) that extends from a muscle and attaches to the periosteum of a bone |
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Term
| bundle (tendon) or sheet (aponeurosis) |
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Definition
| At each end of muscle, the collagen fibers of epimysium, perimysium, and endomysium come together to form a |
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Term
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Definition
| : abroad, flat sheet of tendon joining one muscle to another or to a bone |
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Term
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Definition
narise during embryonic development from the fusion of a hundred or more myoblasts (precursor cell of muscle fiber)
qThis is why each mature skeletal muscle fiber has a hundred or more nuclei
qOnce fusion has occurred, the muscle fiber loses its ability to undergo cell division. |
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Term
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Definition
nMeasurements
qDiameter is 10 – 100 mm.
qLength is 10 cm (4 in.) to 30 cm (12 in.) |
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Definition
nis set before you are born; most of these cells last a lifetime
qA few myoblasts persist in mature skeletal muscle as myosatellite cells to replace damaged or degenerated muscle fibers –VERY LIMITED! |
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Term
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Definition
qPlasma membrane of a muscle cell |
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Term
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Definition
qCytoplasm of a muscle fiber
qSurrounded by sarcolemma
qContains glycogen (large molecule made of many glucose molecules)
nUsed for synthesis of ATP
qContains red-colored protein called myoglobin whichbinds oxygen molecules
nMyoglobin releases oxygen when it is needed for ATP production by mitochondria |
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Term
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Definition
qTiny invaginations of sarcolemma that tunnel in from the surface to the center of each muscle fiber
qOpens to the outside and filled with interstitial fluid |
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Term
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Definition
qMuscle action potentials travel through? |
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Term
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Definition
qThread like structures in sarcoplasm which can actively shorten and are responsible for skeletal muscle contraction
qExtend entire length of muscle fiber and have prominent striations
each muscle fiber has hundreds to thousands of these |
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Term
nSarcoplasmic reticulum (SR) |
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Definition
qMembranous fluid-filled sacs which encircles each myofibril
qSimilar to smooth endoplasmic reticulum
qStores calcium ions (Ca++) (in relaxed muscle fiber)
nRelease of Ca++ triggers muscle contraction |
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Term
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Definition
qFound within myofibrils
qFunction in the contractile process
qTwo types of filaments
nThick – composed mostly of myosin
nThin – composed mostly of actin
qThere are two thin filaments for every thick filament
qThick and thin filaments overlap to a greater or lesser extent depending if muscle is contracted, relaxed, or stretched
nTheir pattern of overlap creates the striations seen in myofibrils and muscle fibers |
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Term
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Definition
qCompartments of arranged myofilaments
qSmallest functional unit of a myofibril
n10,000 sarcomeres per myofibril |
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Term
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Definition
qSeparate one sarcomere from the next
qThin filaments extend from Z line |
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Term
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Definition
qDarker middle part of the sarcomere
qa) Includes entire length of thick filaments and (b) part of thin filaments that overlap with thick filaments (zone of overlap) |
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Term
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Definition
qCenter of each A band which contains thick filaments but no thin filaments |
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Term
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Definition
qContains supporting proteins that hold the thick filaments together in the center of H zone |
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Term
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Definition
qLighter, less dense area of sarcomere that contains thin filaments but no thick filaments
qZ lines passes through the center of each I band |
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Term
Contractile proteins
Regulatory proteins
Structural proteins |
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Definition
| Myofibrils are built from three kinds of proteins |
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Term
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Definition
nGenerate force during contraction
qActin and Myosin |
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Term
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Definition
nSwitch the contraction process on and off
qTroponin and Tropomyosin |
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Term
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Definition
nAbout a dozen of them
nAlign the thick and thin filaments properly
nProvide elasticity and extensibility
nLink the myofibrils to the sarcolemma
qTitin
Dystrophin |
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Term
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Definition
qThick filaments
qFunctions as a motor protein in all three types of muscle tissue
qConverts ATP (chemical energy) to mechanical energy of motion |
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Definition
q300 molecules of myosin form one single thick filament |
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Term
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Definition
qShaped like two golf clubs twisted together:
n1 Myosin tail (twisted golf club handles) points toward M line
n2 Myosin heads (golf club heads) protrude outward in a spiral fashion toward thin filaments
qMyosin heads bind to myosin-binding sites on actin and form crossbridges |
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Term
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Definition
| Myosin heads bind to myosin-binding sites on actin and form |
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Term
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Definition
qFound on thin filaments
qAnchored to Z discs
qIndividual actin molecules join to form an actin filament twisted into a helix
qprovides a sitewhere a myosin head can attach |
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Term
nTropomyosin and troponin |
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Definition
qRegulatory proteins that are also part of the thin filament
nIn a relaxed muscle, myosin is blocked from binding to actinbecause strands of tropomyosin cover the myosin-binding sites
nBinding of calcium ions to troponin moves tropomyosin away from myosin-binding sites
Allows muscle contraction to begin as myosin binds to actin |
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Term
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Definition
qStructural protein that links thin filaments to the sarcolemma
nHelps reinforce the sarcolemma and helps transmit tension generated by sarcomeres to tendons |
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Term
qDuchenne Muscular Dystrophy (DMD) |
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Definition
nMuscle-destroying disease that causes progressive degeneration of skeletal muscle fibers
nMutated gene is on X gene; mainly affects boys
qGene that codes for dystrophin is mutated so little to no dystrophin is in sarcolemma
qWithout dystrophin, sarcolemma tears easily during muscle contraction and muscle fibers rupture and die
nNoticed between ages 2 - 5 when child has difficulty walking, running and falls often
nBy age 12 most boys with DMD cannot walk; by age 20 usually die from respiratory or cardiac failure |
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Term
q1) Myosin heads attach to binding sites on actin filament and bend, pulling on actin filament.
q2) Then the myosin head can release, straighten, combine with another binding site further down the actin filament, and pull again.
nThin filaments are progressively pulled toward the center of the sarcomere (M line)
nThin filaments slide inward and meet at M line
qZ lines come closer together and the sarcomere shortens
nLengths of thick and thin filaments does not change
nH band and I band get smaller
Width of A band remains constant |
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Definition
| Muscle contraction occurs because |
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Term
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Definition
| Muscle cells can pull (but not push); this pull is called |
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Term
nDuring a contraction, sliding occurs in every sarcomere along the myofibril |
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Definition
nShortening of sarcomeres causes shortening of myofibril
nShortening of myofibrils shortens muscle fiber
nShortening of muscle fibers leads to shortening of entire muscle which pulls on tendons attached to bones |
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Term
nMuscle cells can pull (but not push); this pull is called tension |
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Definition
nTension applied to an object tends to pull the object toward the source of tension
nBefore movement can occur, the applied tension must overcome the object’s load or resistance (weight of object, friction, shape, etc.)
nWhen applied tension exceeds the load, the object moves! |
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Term
n1) ATP is available
n2) Ca++ level is sufficiently high in sarcoplasm
n3) Nerve impulse by motor neuron (which generates action potential in muscle fiber) |
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Definition
nThe contraction cycle repeats as long as |
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Term
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Definition
| Muscle action potentials are generated by a nerve impulse at a specialized intercellular connection known as a |
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Term
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Definition
| A motor neuron can activate a muscle fiber by stimulating its sarcolemma and generating a muscle action potential called this starts muscle contraction |
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Term
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Definition
qVIP: An increase in Ca++ concentration in muscle fiber starts contraction and a decrease in Ca++ stops it!!!!!!
qMuscle action potentials moving along sarcolemma and T tubules of muscle fiber cause Ca++ release channels on SR to open – this allows Ca++ to be released into cytosol of muscle cell
qTroponin molecules have binding sites for calcium. Released Ca++ binds with troponin, changes the shape of the troponin-tropomyosin complex rolling tropomyosin away from myosin-binding sites on actin.
Myosin can now form crossbridges with actin and contraction cycle begins |
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Term
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Definition
qMuscle cell membrane contains Ca++ active transport pumps (that use ATP) that are constantly running to return Ca++ back to SR
nDecreases calcium ion levels in sarcoplasm
qAs the Ca++ level in cell drops:
n1) Calcium ions detach from troponin
n2) Troponin returns to its original position
n3) Myosin-binding sites on actin are covered by tropomyosin
n4) Contraction ends and muscle relaxes |
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Term
| Rigor Mortis = “Rigidity of death |
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Definition
nOccurs 2 - 7 hours after death; skeletal muscles undergo partial contraction that fixes the joints.
qAfter cell death, cell membranes become leaky
nCalcium ions leak out of SR into sarcoplasm, and thus allows energized/cocked myosin heads to bind to actin
qBecause no ATP is made, the myosin crossbridges cannot detach from actin
nATP is also needed for calcium active transport pumps to pump calcium ions back into SR
qSo muscles cannot relax and remain in a state of rigidity!
nLasts approx. 1 – 6 days or when decomposition begins with proteolytic enzymes from lysosomes digesting the crossbridges, titin filaments, and Z lines |
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Term
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Definition
nneurons that stimulate skeletal muscles to contract
qMotor neurons have a threadlike axon that extends from the brain or spinal cord to a group of skeletal muscle fibers |
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Term
| Neuromuscular junction (NMJ): |
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Definition
nsynapse of the motor neuron and muscle fiber
qSynapse: where communication occurs between a somatic motor neuron and a muscle fiber (or neuron to neuron)
qMuscle action potentials (electrical signals) arise here |
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Term
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Definition
| where communication occurs between a somatic motor neuron and a muscle fiber (or neuron to neuron) |
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Term
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Definition
nsmall gap thatseparates the two cells at a synapse
Cells do not physically touch |
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Term
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Definition
| chemical released by the initial cell communicating with the second cell |
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Term
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Definition
qNeurotransmitters are used because action potentials cannot “jump” from cell to cell |
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Term
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Definition
nfound at end of motor neuron (axon terminal)
qLots of mitochondria and synaptic vesicles found here |
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Term
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Definition
| sacs suspended within cytosol of synaptic end bulb which contain molecules of the neurotransmitter acetylcholine (ACh) |
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Term
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Definition
nregion of the muscle fiber sarcolemma opposite the synaptic end bulbs
qContains acetylcholine receptors (30 - 40 million)
qSarcolemma is extensively folded
qLots of nuclei and mitochondria here |
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Term
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Definition
nBlocks release of ACh from synaptic vesicles of motor neuron
qIf ACh is not released, no muscle action potential and thus muscle contraction can’t occur!!!!
nMay be found in improperly canned foods
qA tiny amount can cause death by paralyzing respiratory muscles including diaphragm; e.g. breathing stops |
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Term
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Definition
nUsed as a medicine (Botox®)
nStrabismus (crossed eyes)
nBlepharospasm (uncontrollable blinking)
nSpasms of the vocal cords that interfere with speech
nCosmetic treatment to relax muscles that cause facial wrinkles |
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Term
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Definition
nCaused by anaerobic bacterium, Clostridium tetani
nFound virtually everywhere including soil
nThrives in human tissues with low oxygen such as deep puncture wound
nReleases toxin that inhibits suppression of motor neuron activity
qCauses sustained, powerful contractions of skeletal muscles throughout body
nSymptoms include headache, muscle stiffness, difficulty swallowing and opening mouth, and widespread muscle spasms
qUsually resolves after 2-4 weeks with no aftereffects
500,000 cases per year worldwide |
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Term
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Definition
| (severe spasm in which the back arches and the head bends back and heels flex toward the back) in patient suffering from tetanus. |
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Term
nPower the contraction cycle
nPump Ca++ into the SR |
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Definition
qA huge amount of ATP is needed to: |
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Term
nFrom creatine phosphate
n2) By anaerobic cellular respiration
n3) By aerobic cellular respiration |
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Definition
The ATP inside muscle fibers will power contraction for only a few seconds
ATP must be produced by the muscle fiber after ATP reserves are used up
Muscle fibers have three ways to produce ATP?
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Term
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Definition
| Excess ATP is made when muscle fibers are relaxed; it is used to synthesize |
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Term
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Definition
nEnergy-rich molecule only found in muscle fibers |
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Term
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Definition
qis a small, amino acid like molecule that is synthesized in the liver, kidneys and pancreas and then transported to muscle fibers
n3 – 6X more plentiful than ATP in relaxed muscle fiber |
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Term
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Definition
When muscle contraction begins this transfers its high energy phosphate group to ADP regenerating new ATP
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Term
| creatine phosphate and ATP in muscle fibers at start of activity provide enough energy for contraction for about 15 seconds |
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Definition
nSufficient for short bursts of activity e.g. running the 100-meter dash |
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Term
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Definition
nSeries of ATP producing chemical reactions that do not require oxygen |
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Term
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Definition
nGlucose is broken down to generate ATP when the supply of creatine phosphate is depleted
qGlucose is supplied from the blood and/or from glycogen (storage form of glucose) stored in muscle fibers |
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Term
| 2 molecules of pyruvic acid and produces a net yield of two molecules of ATP |
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Definition
| Glycolysisbreaks down glucose into |
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Term
| 30 to 40 seconds of muscle activity |
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Definition
| Anaerobic respiration can provide enough energy for about |
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Term
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Definition
qIf oxygen levels are low, anaerobic reactions convert pyruvic acid to lactic acid which is carried away by the blood to the liver |
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Term
ncytosol of muscle fiber
nOccurs in absence of O2
n1 glucose molecule yields 2 pyruvic acid molecules and net yield of 2 ATP
nIf O2 no available, 2 pyruvic acid molecules converted to 2 lactic acid molecules
qToo much lactic acid lowers pH in muscle fiber and key enzymes can’t work – so muscle fiber cannot contract
nInefficient way to generate ATP |
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Definition
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Term
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Definition
nActivity that lasts longer than half a minute depends on aerobic cellular respiration
qIf sufficient oxygen is present, pyruvic acid formed by glycolysis enters aerobic respiration pathway producing a large amount of ATP in mitochondria
nPyruvic acid entering the mitochondria is completely oxidized (broken down) generating these end-products: ATP, CO2, water, and heat |
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Term
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Definition
| Aerobic respiration yields blank molecules of ATP? |
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Term
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Definition
| Oxygen from blood is stored in red-pigmented protein, found in red blood cells |
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Term
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Definition
| Oxygen stored in reddish-brown pigmented protein in the muscle cell |
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Term
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Definition
only found in muscle cells
reduces muscle’s dependence upon oxygen from blood during muscular contraction |
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Term
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Definition
| Muscle tissue has two sources of oxygen? |
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Term
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Definition
nTakes place in mitochondria
nSupplies ATP for prolonged activity as long as oxygen and nutrients are available
qPyruvic acid, amino acids, fatty acids can all be used as nutrients |
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Term
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Definition
nprovides more than 90% of the needed ATP in activities lasting more than 10 minutes
Marathon - most ATP is produced |
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Term
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Definition
nmuscle loses its ability to contract after prolonged and strenuous activity
qProbably a protective mechanism to stop a person from exercising before muscle become damaged |
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Term
nDamage to sarcolemma and SR
nDepletion of creatine phosphate
nInsufficient oxygen
nDepletion of glycogen, lipid, and amino acid reserves
nBuildup of lactic acid - pH in muscle tissue too low which alters enzyme activities and Ca2+ can’t bind to troponin |
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Definition
qFactors that contribute to muscle fatigue: |
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Term
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Definition
nmuscle undergoes sustained involuntary contraction; painful
qMay be caused by fatigue, electrolyte imbalance (K+), dehydration, and inadequate blood flow to muscles.
qUsually treated with fluid intake and gradual stretching of the muscle |
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Term
| recovery oxygen uptake or oxygen debt |
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Definition
| After exercise, heavy breathing continues and oxygen consumption remains above the resting level |
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Term
| This extra oxygen after breathing heavy is used in several ways: |
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Definition
n1) To convert lactic acid into glycogen stores in the liver
n2) To resynthesize creatine phosphate and ATP in muscle fibers
n3) To replace the oxygen removed from myoglobin
n4) All chemical reactions in body are working at faster pace due to elevated body temperature – needs more ATP – more O2 is needed to make lots of ATP
n5) Tissue repair processes are occurring at increased pace
n6) Heart and muscles associated with breathing are still working harder than at rest, so they use more ATP |
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Term
qTwitches last from 20 to 200 milliseconds (msec)
nDepends on type of muscle, its location, internal and external environmental conditions |
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Definition
nA single stimulus-contraction-relaxation sequence in a muscle fiber |
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Term
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Definition
qA brief delay between the stimulus (time 0 on graph) and muscular contraction
qThe action potential sweeps over the sarcolemma and Ca++ is released from the SR |
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Term
nContraction period (10 – 100 msec) |
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Definition
qCa++ binds to troponin and myosin-binding sites on actin are exposed
qCross-bridges form and peak tension in muscle fiber develops |
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Term
| Relaxation period (10 –100 msec |
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Definition
nCa++ is transported into the SR
nMyosin-binding sites are covered by tropomyosin
nMyosin heads detach from actin
nTension in muscle fiber decreases |
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Term
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Definition
qWhen a muscle fiber contracts, it temporarily cannot respond to another action potential
nCharacteristic of muscle and nerve cells
qSkeletal muscle has a refractory period of 5 milliseconds
qCardiac muscle has a refractory period of 300 milliseconds |
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Term
q1) Tension produced by stimulated individual muscle fibers
nHigher the number of cross-bridges made during contraction the higher the tension in muscle fiber
q2) Total number of muscle fibers stimulated |
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Definition
| Amount of tension produced in skeletal muscle as a whole is determined by |
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Term
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Definition
| consists of one motor neuron and all the skeletal muscle fibers it stimulates |
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Term
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Definition
qA single motor neuron makes contact with about 150 muscle fibers and all the muscle fibers in one motor unit contract and relax in unison
qTypically muscle fibers of a motor unit are dispersed throughout a muscle rather than clustered together
qThe total strength of a contraction (tension) depends, in part, on the size of the motor units and the number that are activated |
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Term
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Definition
| occurs when all motor units in the muscle contract.ccccccccc |
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Term
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Definition
nA small amount of tension or tautness in a muscle due to some of its motor units are active when the muscle is at rest |
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Term
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Definition
nis a response to non-stop nerve impulses from brain and spinal cord that stimulates a few motor units.
qBasically, small groups of the muscle’s motor units are contracting, while others are relaxed in a constantly shifting pattern |
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Term
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Definition
nis important in maintaining body posture, otherwise the body would collapse!
qSkeletal muscles in back of neck in tonic contraction keeps head upright
qMuscle tone in smooth muscle in walls of blood vessels maintain blood pressure |
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Term
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Definition
qThe tension (force of contraction) developed by the muscle remains constant while the muscle changes its length
nBasically a load or object and parts of the skeleton is moved.
nUsed for body movements and for moving objects
Ex.: Picking a book up off |
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Term
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Definition
qThe tension generated is not enough for the object to be moved and the muscle does not change its length
nBasically bones and the object do not move
nUsed for maintaining posture and for supporting objects in a fixed position
Ex.: Holding a book steady using an outstretched arm, straining to lift a weight that is too heavy for you |
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Term
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Definition
nHave a high myoglobin content
nAppear darker (dark meat in chicken legs and thighs) |
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Term
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Definition
nHave a low content of myoglobin
Appear lighter (white meat in chicken breasts |
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Term
q1) Slow oxidative fibers
q2) Fast oxidative-glycolytic fibers (Intermediate fibers)
q3) Fast glycolytic fibers |
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Definition
nMuscle fibers contract at different speeds, and vary in how quickly they fatigue
nMuscle fibers are classified into three main types: |
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Term
Slow Oxidative Fibers (SO fibers)
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Definition
nSmallest in diameter
nLeast powerful type of muscle fibers
nAppear dark red (more myoglobin & blood capillaries)
nGenerate ATP by aerobic cellular respiration
qContains lots of mitochondria
nHave a slow speed of contraction
qATPase in myosin heads hydrolyses ATP relatively slowly
qTwitch contractions last from 100 to 200 msec
nVery resistant to fatigue
nCapable of prolonged, sustained contractions for many hours
Adapted for maintaining posture and for aerobic, endurance-type activities such as running a marathon |
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Term
| Fast Oxidative–Glycolytic Fibers (FOG fibers) |
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Definition
nIntermediate in diameter between the other two types of fibers
nHas a red-pink appearance (large amounts of myoglobin and many blood capillaries)
nGenerate lots of ATP by aerobic cellular respiration and some by anaerobic glycolysis
qContains lots of mitochondria
nModerately high resistance to fatigue
nSpeed of contraction faster
qATPase in myosin heads hydrolyses ATP 3 - 5 times faster than SO fibers
qTwitch contractions last less than 100 msec
Contribute to activities such as walking and sprinting |
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Term
| Fast Glycolytic Fibers (FG fibers) |
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Definition
nLargest in diameter (contain most myofibrils)
nGenerate the most powerful contractions
nAppear white in color (low myoglobin content and few blood capillaries)
nFew mitochondria
nGenerate ATP mainly by anaerobic glycolysis
nFibers contract strongly and quickly
nFatigue quickly
nAdapted for intense anaerobic movements of short duration
qWeight lifting or throwing a ball
nFG fibers of a weight lifter may be 50% larger than sedentary person or endurance athlete
qIncrease in size due to increased synthesis of muscle proteins (actin and myosin) NOT increase in muscle cells! |
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Term
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Definition
| Continually active postural muscles of the neck, back, and legs have a high proportion of |
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Term
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Definition
| Muscles of the shoulders and arms are not constantly active and have a high proportion of |
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Term
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Definition
| Leg muscles used for body support and running and walking have large numbers of both |
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Term
qIndividuals with a higher proportion of FG fibers: |
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Definition
| Excel in intense activity (weight lifting, sprinting |
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Term
qIndividuals with higher percentages of SO fibers: |
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Definition
nExcel in endurance activities (long-distance running) |
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Term
| Exercise and Skeletal Muscle Tissue |
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Definition
nIf a muscle is used repeatedly for endurance events, some of its FG fibers can change to FOG fibers so the muscle will become more resistant to fatigue
qHowever, SO fibers cannot change to FOG/FG fibers |
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Term
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Definition
nMuscle enlargement is due to increase in diameter of muscle fibers from increased production of thick and thin filaments, myofibrils, mitochondria, glycogen, SR and other organelles - NOT FROM INCREASE IN NUMBER OF MUSCLE FIBERS!
qResults from repetitive muscular activity at near-maximal tension (strength or weight training)
qStrength of muscular contraction is directly proportional to diameter of activated muscle fibers. So bigger muscles can contract more forcefully than smaller ones. |
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Term
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Definition
nWasting away of muscles
qIndividual muscle fibers decrease in size due to loss of myofibrils |
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Term
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Definition
qatrophy that occurs because muscles are not being used
nBedridden individuals or people with casts
nCondition is reversible |
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Term
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Definition
qnerve supply to muscle is cut or disrupted
nAfter 6 months to 2 years, muscle shrinks to ¼ its size and muscle fibers irreversibly replaced with fibrous connective tissue |
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Term
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Definition
nFound only in the walls of the heart
nStriated like skeletal muscle
nTypically branched with 1 - 2 centrally located nuclei
nHas the same arrangement of actin and myosin as skeletal muscle fibers
qContains same zones, bands and Z discs
nIntercalated discs connect the ends of cardiac muscle fibers to one another
qAllow muscle action potentials to spread from one cardiac muscle fiber to another quickly |
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Term
| Cardiac Muscle Tissue Cont |
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Definition
nAction is involuntary
qContraction and relaxation of the heart is not consciously controlled (autonomic nervous system)
nCardiac muscle tissue contracts when stimulated by its own autorhythmic muscle fibers (NOT neural stimulation like skeletal muscle)
qContinuous, rhythmic activity is a major physiological difference between cardiac and skeletal muscle tissue
nContractions lasts longer than a skeletal muscle twitch
nDue to continuous, rhythymic activity, depends on aerobic respiration to generate ATP
qRequires a constant supply of oxygen
qHas lots of mitochondria, myoglobin and lipid and glycogen reserves |
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Term
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Definition
nLong, slender cells with 1 centrally located nucleus
nContains actin and myosin filaments but no myofibrils or sarcomeres
qThus, lacks the striations of skeletal and cardiac muscle tissue
nNo T tubules
nThin filaments are bound to dense bodies that anchor thin filaments during contraction
nUsually involuntary contractions (autonomic nervous system) |
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Term
| Two types of smooth muscle |
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Definition
q) Visceral smooth muscle
q2) Multiunit smooth muscle |
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Term
| Visceral Smooth Muscle Tissue |
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Definition
Muscle fibers are arranged in sheets
qFound in nwalls of hollow organs, e.g. stomach, intestines uterus, ureter, urinary bladder and walls of small arteries and veins
qAutorhythmic
nMuscle fibers can stimulate each other – self-exciting
qWhen one fiber is stimulated, the muscle action potential is spread to neighboring fibers, which then contract in unison, as a single unit |
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Term
| Multiunit Smooth Muscle Tissue |
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Definition
nFound in large blood vessels, large airways to lungs, arrectorpili muscles that pull on hair follicles, and the eye, where it adjusts pupil diameter and lens focus
qFibers operate independently rather than in unison
nStimulation of one multiunit fiber causes contraction of that fiber only. |
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Term
| Physiology of Smooth Muscle |
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Definition
nContraction starts more slowly and lasts longer than skeletal and cardiac muscle contraction
nAble to sustain long-term muscle tone
qImportant in the:
nGI tract where a steady pressure is maintained on the contents of the tract
nIn the walls of blood vesselswhich maintain a steady pressure on blood |
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Term
Physiology of Smooth Muscle Cont.
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Definition
nMost smooth muscle fibers contract or relax in response to:
qAction potentials from the autonomic nervous system
qIn response to stretching
nFood in GI tract stretches intestinal walls initiating peristalsis
qHormones
nEpinephrine causes relaxation of smooth muscle in the air-ways and in some blood vessel walls
qChanges in pH, temperature, oxygen and carbon dioxide levels |
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Term
| Regeneration of Muscular Tissue |
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Definition
nSkeletal muscle has limited regenerative abilities
qGrowth of skeletal muscle after birth is due mainly to hypertrophy
qMyosatellite cells divide slowly and fuse with existing fibers
nAssist in muscle growth and repair of damaged fibers
nCardiac muscle can, under certain circumstances, regenerate
nCardiac muscle can undergo hypertrophy in response to increased workload
qMany athletes have enlarged hearts
nSmooth muscle tissue, unlike the other two, can regenerate and undergo cell division to a certain extent
nSmooth muscle can undergo hypertrophy |
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Term
| Aging and Muscular Tissue |
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Definition
nAging brings a progressive loss of skeletal muscle that is replaced with fibrous connective and adipose tissue
qDue in part to decreased physical activity and loss of certain hormones
nWill start by age of 40!!!!!!!!
nLoss of muscle mass leads to:
qA decrease in maximal strength
qA slowing of muscle reflexes
qA loss of flexibility
nTo be in good shape late in life, you must be in very good shape earlier in life.
qAerobic activities and strength training can slow the decline in muscular performance |
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