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| Motion of skeleton, stabilizes body position, regulates organ volume to store and release materials, moves substances within the body, thermogenesis |
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Electrical excitability-muscle action potentials
Contractibility
Extensibility
Elasticity |
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| sheet of fibrous C.T. that surrounds muscles and other body organs |
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| separates muscle from skin and is composed of adipose and aerolar C.T. |
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| Dense irregular C.T. that lines the body wall and also holds muscles with similar functions together |
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| Outer most layer which surrounds muscle |
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| Thin sheath of aerolar C.T. around each muscle fiber |
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| stimulate skeletal muscle to contract |
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| axons branch inside muscle branch inside these and they extend to different muscle fibers |
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| Cord of dense regular C.T. that attaches muscle to bone periosteum |
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| Axon terminals expand into these |
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| Connection between the neuron and the muscle fiber |
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| cells in mature muscle that retain the capacity to regenerate muscle fibers |
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| muscle is well supplied with blood so that each fiber is in close contact with blood capillaries |
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| Plasma membrane of a muscle fiber |
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| tiny invagination of the sarcolemma that tunnel into each fiber and are filled with ECF- allow action potential to spread rapidly throughout cell (depolarizes membrane of t tubule) |
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| Muscle fiber's cytoplasm - contains glycogen and myoglobin |
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Modified ER of muscle fibers that stores Ca2+ and ends in terminal cisterns near T Tubules
*depolarization causes SR to release calcium into muscle cells |
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| Lengthwise threads inside and extend the entire length of the fiber-contain sarcomeres |
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| thin and thick filaments arranged in compartments |
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| Functional Units of a myofibril |
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| sarcomeres connected end to end and are functional units of a myofibril |
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Definition
NMJ is the site where signal to contract is passes from the neuron to the fiber.
on the neuron side of the synaptic cleft between the neuron and fiber is synaptic end bulb
muscle side=motor end plate |
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| How action potentials arise at NMJ |
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Definition
Nerve impulses-release of Ach-activation of Ach receptors-muscle action potential-termination of Ach activity
*Ach diffuses into the synaptic cleft to the motor end plate and binds to receptors on sarcolemma which opens ion channels which allow Na+ to rush in and generate muscle action potential |
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| Thick and thin filaments overlap eachother in a patter that creates this ___________ |
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| Thick filaments and serves as motor proteins to move thin filaments - bind to myosin heads that will bind to thin filaments to move them |
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| Thin filaments and contains myosin binding sites that will bond to the myosin heads to move actins during contraction |
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| covers myosin binding sites on actin to prevent contraction in resting muscle |
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| Holds tropomyosin in place |
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| gives elasticity and extensibility to myofibrils by stretching and then springing back |
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| Links thin filaments to sarcolemma to strengthen it and help transmit force to tendons |
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| Muscle fiber cell simplified |
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Definition
| sarcomeres-dystrophin- t tubules-terminal cisterns-SR-sarcoplasm |
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| Sliding filament mechanism of muscle contraction |
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Definition
1. muscle action potential reaches terminal cisterns and stimulates Ca2+ channels to open and release calcium into surround sarcoplasm
2. calcium bonds to troponin on thin filaments and causes troponin-tropomyosin complex to shift and uncovers myosin binding sites on actin
3. energized myosin head bonds to actin to form cross bridge and pulls actin toward center
4. atp bonds to myosin head and it is broken down and its energy causes the head to detach, rotate, and reattach furth down filament
5. myosin head swivels and pulls further toward center
6. repeated as long as calcium is present |
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Definition
Ach-esterase breaks down Ach transmitter at motor end plate so that muscle action potentials are no longer generated and calcium channels close
-calcium is pumped back into terminal cisterns so that Trop-tropom shifts back to cover the myosin and stops muscle contracting |
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| Length Tension Relationship |
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Definition
| Muscle fiber develops its greatest tension when there is optimal zone of overlap between thick and thin filaments |
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Provides enough energy for maximal contraction for about 15 seconds
*stored in muscles and then transfers its high energy phosphate group to ADP to make ATP |
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| Anaerobic Cellular Respiration 1 |
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Definition
| Provides energy for 30-40 seconds and it occurs when O2 is not available for aerobic cell respiration |
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| Anaerobic Cell Respiration 2 |
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Definition
1.glucose is broken down into pyruvic acid (glycolysis) and produces 2 ATP per glucose
2. if O2 isnt available, most of py-acid is broken down into lactic acid and most of this diffuses back into blood to be converted back to glucose in liver
3. anaerobic process because it does not require O2 |
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| Aerobic Cell Respiration 1 |
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Definition
| Provides ATP in muscle activity that lasts longer than 30 seconds |
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| Aerobic Cell Respiration 2 |
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Definition
1. Presence of O2, py-acid is not broken down into lactic acid, but it is broken down into CO2 and water in mitochondria-36 ATP produced
2. also fatty acids and amino acids can be broken down |
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Definition
| consists of one somatic motor neuron and all of the muscle fibers it stimulates |
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| all of the fibers of one motor unit contract and relax together--can control the strength of a contraction by the number and size of motor units stimulated |
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Brief contraction all of muscles fibers in motor unit in response to one action potential from somatic motor neuron-4 phases
1.latent period
2.contraction period
3.relaxation period
4.refractory period |
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| time between application of stimulus and begining of a contraction-calcium is being released from SR and filaments start to exert tension as slack is removed from elastic components |
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| calcium is actively pumped into SR |
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| time when fiber cannot respond to another stimulus-toliet flush |
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| number of nerve impulses arriving at NMJ per second and is the main factor that determines a muscle fibers tension |
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| if subsequent stimuli arrive before a muscle fiber has finished relaxing, then they will produce a stronger contraction |
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| shows no discernible twitches |
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| shows discernible twitches |
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| process in which number of motor unit activated increases - helps produce smooth fine movements |
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| Size of motor units activated |
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Definition
larger-stronger
smaller-more precise |
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Small amount of tension in muscle due to weak involuntary contractions
*muscle becomes flaccid |
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| muscle does not shorten, develops tension |
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| tensions stays almost constant while muscle shortens to move a load |
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contain many mitochondria and a lot of myoglobin and have many blood capillaries
*very resistant to fatigue (neck muscles) |
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contain many mitochondria, blood capillaries and myoglobin *split ATP rapidly and are moderately resistant to fatigue
(leg muscles of sprinters) |
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Generate ATP by glycolysis
Relative few mitochondria, blood capillaries, and have relatively low amounts of myoglobin.
Split ATP rapidly but have the lowest resistance to fatigue. E.g. in arm muscles |
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| Effects of exercise on skeletal muscle fibers |
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Definition
endurance exercise causes some fast glycolytic fibers to transform into fast oxidative glycolytic
strength exercise increases size and strength of fast glycolytic fibers and thus the size of the muscles |
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| Single unit smooth muscle tissue |
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Definition
| visceral smooth muscle tissue- occurs in walls of small arteries, veins, and hollow organs |
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| Multiunit smooth muscle tissue |
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Definition
| occurs in airways, large artery wall, arrector pilli muscles, and eye muscles- fine precise smooth muscle motor control |
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| Sarcoplasm of smooth muscle |
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Definition
| contains both thick and thin filaments which are not organized into sarcomeres |
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| Characteristics of smooth muscle fibers |
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Definition
-contractions start more slowly than in other muscle
-last longer-smooth muscle tone
-contract in response to autonomic nervous system
-can stretch and still maintain contractile function |
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| Regeneration of skeletal muscle |
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Definition
-limited due to replacement of damaged muscle fibers by fibrous scar tissue (fibrosis)
satellite cells help in regeneration |
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| Regeneration of cardiac muscle |
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Definition
-lacks satellite cells and has low regeneration capabillity
-stem cells may migrate from blood to form new muscle fibers |
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| Regeneration of smooth muscle |
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Definition
-greatest power of regeneration
-retains capacity to divide
-pericytes can form new smooth muscle |
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Definition
-muscle fibers in iris and arrector pilli---ectoderm
-all other muscles ---mesoderm |
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| Aging effects on skeletal muscle tissue |
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Definition
loss of muscle mass
decrease in maximal strength
muscle reflexes slow down
loss of flexibility
slow oxidative fibers increase |
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Definition
| inherited disease-degeneration of muscle fibers |
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| weakness of skeletal muscles by blockage of impulse transmission at neurotransmitter junction |
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| affects fibrous c.t. of muscles, tendons and ligaments |
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| involuntary brief twitch of motor unit visible under skin |
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| involuntary twitches of s single muscle fiber but is not visible under skin |
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| pain associated with muscles |
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| pathological softening of muscle tissue |
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| inflammation of muscle fibers |
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| muscular excitability and contractibility with decrease power of relaxation |
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| permanent shortening and lack of extensibility due to replacement of destroyed muscle fibers by fibrous connective tissue |
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