Term
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Definition
| a decrease in the negative resting membrane potential. |
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Term
| RESTING MEMBRANE POTENTIAL |
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Definition
| the voltage that exists across a cells; plasma membrane when the cell is at rest; cell interior is relatively more negative that the cells exterior |
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Term
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Definition
| the depolarization and repolarization of a membrane |
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Term
| 3 TYPES OF MUSCLE TISSUE ARE |
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Definition
SKELETAL-attatched to bones and skin; striated; voluntary; and pwerful
CARDIAC MUSCLE TISSUE- only in the heart; striated;involunatry
SMOOTH MUSCLE TISSUE- in the walls of hollow organs like the stomach, urinary bladder, and airways. it is nonstriated and involuntary |
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Term
| 4 SPECIAL CHARACTERISTICS OF MUSCLE TISSUE |
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Definition
1. excitability(responsiveness or irritability)ability to recieve and respond to stimuli
2. contractiity- ability to SHORTEN when stimulated
3. Extensibility- ability to be stretched
4. Elastiticity- the ability to recoil to resting length |
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Term
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Definition
1. movement of bones or fluids (ex:blood)
2. maintaining posture and body position.
3. stabilizing joints
4. heat generation(especially skeletal muscle) |
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Term
| SKELETAL MUSCLE: EACH MUSCLE IS SERVED.... |
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Definition
| by one artery, one nerve and one or more viens |
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Term
| 3 CONNECTIVE TISSUE SHEATHS OF SKELETAL MUSCLE |
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Definition
EPIMYSIUM- dense regular connective tissue surrounding entire muscle.
PERIMYSIUM- fibrous connective tissue tissue surrounding fascicles(groups of muscle fibers)
ENDOMYSIUM- fine areolar connective tissue surrounding each muscle fiber |
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Term
| MICROSCOPIC ANATOMY OF A SKELETAL MUSCLE FIBER |
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Definition
-cylindrical cell 10 to 100 uM in diameter and up to 30 cm long.
- have multiple peripheral nuclei.
-many mitochondria
-glycosomes for glycogen(animal starch) storage, myoglobin for o2 storage.
- also contain myofibrils, sarcoplasmic reticulum(smooth ER) and T tubules |
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Term
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Definition
- densly packed rodlike elements
-80% of cell volume
- they exibit striations: perfectly aligned repeating series of dark A bands and light I bands |
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Term
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Definition
-the smallest contractile unit(funtional unit) of a muscle fiber.
- the region of a myofibril between 2 sucessive Z discs.
- composed of thick and thin filaments made up of contractile protiens |
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Term
| ULTRASTRUCTURE OF THICK FILAMENT |
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Definition
-composed of the protien MYOSIN and myosin tails contain 2 interwoven heavy polypeptide chains.
- myosin head contains: 2 smaller light polypeptide chains that act as crossbridges during contraction; they are binding sites for actin of thin filaments, ATP, and ATPhase enzymes. |
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Term
| ULTRASTRUCTURE OF THIN FILAMENTS |
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Definition
twisted double strand of fibrous protien F ACTIN. F actin consists of globular actin subunits; G actin bears active sites for myosin head attatchment during contraction.
-tropomyosin and troponin: regulatory protiens bound to actin. |
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Term
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Definition
-consists of a network of smooth endoplasmic reticulum surrounding each myofibril.
-have pairs of terminal cisternae form perpendicular cross channels.
-funtions in the regulation of intracellular ca2+ levels |
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Term
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Definition
- allow action potential to go deep into the cell; its continuous with sarcolemma and penetrate the cells interior at each a band and i band juntion.
-associate with the paired terminal cisternae to for triads that encircle each sarcomere |
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Term
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Definition
-T tubules conduct impulses deep into muscle fiber
-integral protiens protrude into the intermembranous space from T tubule and SR cisternae membranes.
-T tubule protiens: voltage sensors.
-SR foot protiens: gated channels that regulate ca2+ release from the SR cisternae |
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Term
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Definition
-the generation of force
-does not nessecarily cause shortening of the fiber
-shortening occurs when tension gathered by crossbridges on the thin filaments exceeds forces opposing shortening |
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Term
| SLIDING FILAMENT MODEL OF CONTRACTION |
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Definition
- in the relaxed state, thick and thin filaments overlap only slightly.
-during contraction, myosin heads bind to actin, detatch and bind again to propel the thin filaments toward the M line.
-as H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle cell shortens |
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Term
| REQUIREMENTS FOR SKELETAL MUSCLE CONTRATION |
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Definition
- ACTIVATION- neural stimulation at a neuromuscular juntion.
- EXITATION-CONTRACTION COUPLING-generation and propagation of an action potential along the sarcolemma. final trigger is a brief rise in intracellular CA2+ levels |
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Term
| EVENTS AT THE NEUROMUSCULAR JUNTION |
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Definition
-skeletal muscles are stimulated by somatic motor neurons.
- axons of motor neurons travel from the central nerves to skeletal muscles.
- each axon forms several branches as it enters a muscle.
-each axon ending forms a neuromuscular juntion with a single muscle fiber. |
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Term
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Definition
- situated midway along the length of a muscle fiber.
- axon terminal and muscle fiber are separated by a gel-filled space called the synaptic cleft.
-synaptic vessels of axon terminal contain the neurotransmitter acetylcholine ACh
-juntional folds of the sarcolemms contain ACh receptors. |
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Term
| more EVENTS AT THE NEUROMUSCULAR JUNTION |
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Definition
- nerve impulse arrives at axon terminal.
-ACh is released and binds with receptors on the sarcolemma.
-electrical events lead to the generation of and action potential. |
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Term
| DESTRUCTION OF ACETYLCHOLINE (ACh) |
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Definition
-ACh effects are quickly terminated by the enzyme acetylcholinesterase.
-prevents continued muscle fiber contration in the absence of additional stimulation. |
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Term
| STEP 1: LOCAL DEPOLARIZATION(end plate potential) |
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Definition
ACh binding opens chemically(ligand) gated ion channels.
- simultaneous diffusing of Na+(inward) and K+ (outward)
-more Na+ diffuses, so the interior of the sarcolemma becomes less negative.
- local depolarization- end plate potential. |
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Term
| STEP 2: GENETATION AND PROPAGATION OF AN ACTION POTENTIAL |
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Definition
-end plate potential spreads to adjacent membrane areas.
-Voltage gated Na+ channels open
- Na+ influx decreases the membrane voltage toward a critical threshold.
- If threshold is reached, and action potential is generated
-events at the generation of an action potential: local depolarization wave continues to spread changing the permeability of the sarcolemma and voltage regulated Na+ channels open in the adjacen patch, causing it to depolarize the threshold |
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Term
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Definition
- Na+ channels close and voltagegated k+ channels open.
- K+ efflux rapidly restres the resting polarity.
-Fiber cannot be stimulated and is in refractory period until repolarization is complete.
-ionic conditions of the resting state are restored by the Na+-K+ pump |
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Term
| EXITATION-CONTRACTION(E-C) COUPLING |
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Definition
-sequence of events by which transmission of an AP along the sarcolemma leads to sliding of the myofilaments
- latent period: time when e-c coupling events occur; time between AP initiation and the beginning of contraction. |
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Term
| EVENTS OF EXITATION-CONTRACTION (E-C) COUPLING |
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Definition
- AP is propogated along sarcomere to T tubules
-Voltage-sensitive protiens stimulate Ca2+ release from SR; ca2+ is nessecary for contraction. |
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Term
| ROLE OF CALCUIM(CA2+0 in contraction at low intracellular ca2+ concentration |
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Definition
- tropomyosin blocks the active sites on actin
- myosin heads cannot attatch to actin
- muscle fiber releases |
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Term
| ROLE OF CALCUIM (CA2+)IN CONCENTRATION AT HIGHER INTRACELLULAR CA2+ LEVELS |
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Definition
-CA2+ BINDS TO TROPONIN
- TROPONIN CHANGES SHAPE AND MOVES TROPOMYOSIN AWAY FROM ACTIVE SITES
OO- EVENTS OF THE CROSSBRIDE CYCLE OCCUR.
- WHEN NERVOUS STIMULATION CEASES, CA2+ IS PUMPED BACK INTO THE SR AND CONTRACTION ENDS. |
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Term
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Definition
- continues as long as the ca2+ signal and adequate ATP are present.
- cross bridge formation- high energy myosin head attatches to thin filament.
-working (power) stroke- myosin head pivots and pulls thing filament toward M line.
-cross bridge detatchment- ATP attatches to myosin head and the crossbridges detatches
- "cocking" of the myosin head- energy of hydrolosis of ATPcocks the myosin head into the high energy state. |
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Term
| 3 PRINCIPLES OF MUSCLE MECHANICS |
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Definition
- same principle apply to contraction of a single fiber and a whole muscle.
-contraction produces tension, the force exerted on the load or object to be moved.
- Contraction does not always shorten a muscle.
- isometric contraction- no shortening; muscle tension increases but does not exceed the load.
- isotonic contraction- muscle shortens because muscle tensionn exeeds the load |
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Term
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Definition
| no shortening; muscle tension increases but does not exceed that load. |
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Term
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Definition
| muscle shortens because muscle tension exceeds the load. |
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Term
| FORCE AND DURATION OF CONTRACTION VARY IN RESPONCE TO STIMULI OF DIFFERENT FREQUENCIES AND INTENSITIES.(MOTOR UNIT IS THE NERVE MUSCLE FUNTIONAL UNIT) |
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Definition
-motor unit is a motor neuron and all (4- several 100) muscle fibers it supplies. small muscle fibers control fine movements(fingers and eyes) while large motor units in large weight bearing muscles (thighs and hips)
- in motor units: muscle fibers from a motor unit are spread throughout the muscle so that a single motor unit causes a weak contraction of entire muscle.
-motor units in a muscle usually contract asynchronously: helps prevent fatigue |
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Term
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Definition
| - responce of a muscle to a single , brief threshold stimulus |
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Term
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Definition
- when muscle changes in length and moves the load.
- isotonic contractions are either concentric or eccentric. CONCENTRIC CONTRATIONS- the muscle shortens and does work. Ex: like flexing arm-picking up book. ECCENTRIC CONTRACTION- the muscle contacts as it lengthens;eX: like something too heavy for arm. |
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Term
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Definition
- no shortening or lengthening
-the load is greater than the tension the muscle is able to develop.
- tension increases to the muscles capacity, but the muscle neither shortens or lengthens. ex: trying to push down a brick wall |
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Term
| MUSCLE METABOLISM: ENERGY FOR CONTRACTION |
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Definition
- atp is the only source used directly for contractile activities.
- available sources of atp are depleated in 4 to 6 seconds.
-ATP is generated by: DIRECT PHOSPHORYLATION FO ADP BY CREATINE PHOSPHATE (CP)-reserver of phosphate; gives muscles energy.
ANAEROBIC PATHWAY- (glycosis)- respiration with out oxygen.
AEROBIC RESPIRATION- very efficient |
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Term
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Definition
- at 70 % of maximum contractile activity: bulging muscles compress blood vessels, oxygen delivery is impaired, and pyruvic acid is converted into lactic acid
-lactic acids used as fuel by the liver, kidney, and heart and are converted back into pyruvic acid by the liver |
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Term
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Definition
- produces 95% of ATP during rest and light to moderate exercise.
- we use these as fuels: stored glycogen, then bloodbourne glucose, pyruvic acid from glycosis, and free fatty acids |
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