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21 Cards in this Set

  • Front
  • Back
Define Contractility
Capacity of MS fiber to undego shortening and change shape, becoming thicker
These sections shorten and become thick because the Actin filaments move toward the center this is constitues contraction
Cross Bridges
Myosin extensions that latch on to Actin and pulls them toward the center, shortening the Sarcomeres
-Energy needed to pull Actin strands together
-Require oxygen and glucose
Sliding Filament Theory
Myson crossbridges attach to the Actin filament and bends, pulls on Actin it then releases and attaches to the next Actin binding site, pulling again. As long as ATP is avail and MS fiber is stimulated this will continue.
Stimulus for MS Contraction
-Acetylchlorine released from synaptic vesicle
-Motor end plate detects the neurotransmitter and MS IMPULSE spreads over the sacrolemma into the T tubules to the SR
-SR releases calcium to the sarcoplasm of the MS fiber
-calcium trigger and expose the Actin binding sites
-Sarcomere shorten (contraction occurs)
2 Events of Relaxation
1-enzyme breaks down the acetylcholine to prevent continuous stimulation of the MS fiber
2-Calcium returns to SR, LINKS ARE BROKEN between myosin and actin which causes relaxation
Threshold Stimulus
Required stimuli for MS respond.
**Usually enought acetylcholine to reach a threashold stimuli is avail
"All or None"
When MS gets threshold stimui it will respond to its fullest extent
**Increased stimuli will not affect a stronger MS response
A single contraction lasting a fraction of a second when some motor units are stimulated
Fast Twitch Fibers
-Power fibers
-Prone to Fatigue
-Develope bigger in diameter MS
Slow Twitch Fibers
-Endurance fibers
-Fatigue resistant
-Develop more capallaries
-Sustained contraction lacking even partial relaxation
-Spasm, like lockjaw
All Motor units are activated and MS fibers are stimulated..."all or none"
Sustained Contraction
Recruitment (firing of MS)
Summation (series twitching)
acting together
Muscle Tone
Appear at rest, but some sustained contraction is happening: posture
Maintenance of tone due to the action of the nervous system keeping MS in a constant state of readiness
-Develop tension
-To cause or control joint movement
-dynamic contractions: varying degrees of tension change joint angles
-no change in MS length but there's increase in MS tension
2 types of Isotonic contractions
1) Concentric: shortening of MS
2) Eccentric: No shortening of MS, but lengthening with control, which creats tension
Joint angle changes without MS contraction