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CH 6 Biomechanics of skeletal muscle

What are the 4 principle characteristics of muscle tissue? Excitability, Contractility, Extensibility, Elasticity
Excitability Ability to receive an respond to a stimulus
Contractilty (irritability) ability of a muscle to contract and produce a force
Extensibility ability of a muscle to be stretched without tissue damage
Elasticity ability of a muscle to return to its original shape after shortening or extension
How many muscle fibers make up one cell? 1
How long is an individual muscle fiber? 1mm to 600mm
What determines strength? Muscle fiber diameter
Why is muscle fiber important? influences fiber contraction and muscle shortening
What is muscle connective tissue? allows for structural support and force transmission
3 layers of Connective Tissue? Epimysium, Perimysium, Endomysium
Epimysium Wraps entire muscle; tough outer coat
Perimysium Wraps fascicles; provided pathway for major blood vessels and nerves
Endomysium Wraps fibers
Satellite cells -involved in muscle repair -stimulate during muscle training
Where is the satellite cell located? between plasmalemma and basement membrane
Muscle repair steps 1. injuried muscle fiber 2. proliferation & migration of satellite 3. fusion of myoblasts 4. myofibrilar synthesis & assembly 5. Regenerated muscke fiber 6. Become nucleli
Sarcolemma sheath around the fibers of skeletal muscle
Sarcoplasmic reticulum specialized type of smooth Endoplasmic reticulum that regulates the calcium
Transverse Tubule (T-tubules) extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.
Myofibrils Units responsible for contraction & relaxation
How many myofibrils are in 1 muscle fiber? thousands (1000-8000)
What happens when a muscle grows? myofibrils increases
Thick filaments -myosin -A-Band
Thin filaments -actin -I-Band
I-band light colored
A-band Dark color
Z-line -The support of the thin filament -line between the I-band
M-line -The support of the thick filament -line between the A-band
Does the I-band shorten? No, it slide past
Why doesn't myosin pull at the same time? they lose force
H-zone Thick filament where there is no overlap of actin
How is force generated? by a muscle fiber that is directly proportional to the # of myosin cross-bridges that are strongly bound to the actin filament
What allows the cross-bridges to attach to the actin? (on-off switch) Calcium and troponin
What causes the sacrolemma to have an action potential? Synaptic clef
Excitation-contraction coupling t-system signals the release of calcium on-off switch
How does a muscle contract & relaxation 1.Generated action potential 2.Release ACh from presynaptic nerve terminal 3.Binding ACh on muscle fiber 4.Depolarization of sarcolemma 5.Action potential through T-tubules 6.Signaling SR to release calcium 7.Calcium bind to troponin
How does a muscle contract & relaxation(2) 8. tropomyosin exposes binding sites 9.Actin-myosin interaction 10.Pumping calcium back into SR 11.Troponin.Tropomyosin takes back actin/myosin 12.Muscle relaxation
Innervation Ratio # of muscle fibers for that motor neuron 1 motor neuron : # of fiber muscles
Why does fast twitching reach peak force faster than slow twitch? Calcium pumps in the SR with faster isoforms
Sedentary people 50% slow 50% fast where athletes may differ
How to change type IIX -> IIA both strength training & endurance
how to change type IIA -> I extensive endurance training
Agonist acts to cause a movement
Antagonist acts to slow or stop movement
Stabilizer acts to stabilize a body part against some other force
Neutralizer acts to eliminate an unwanted action produced by an agonist
Synergist acts to perform the same action as another muscle
When muscles work as agonist, what type of contraction? Concentric (against resistance)
What are the types of contractions? concentric, eccentric, isometric
Concentric shortening (against)
Eccentric lengthening (with)
Isometric no lengthening
Created by: rmart11



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