Skeletal Muscle Contraction

Step 1

ATP Hydrolysis

ATP Hydrolysis

ATP loses a phosphate group, energizes myosin heads

Step 2

Attachment of myosin to actin to form crossbridges

Step 3

Power Stroke

Power Stroke

Rotates myosin head towards center of sarcomere, releases ADP, thin filament slides past thick

Step 4

Detachment of myosin from actin

Calcium

Ion that starts muscle contraction

Active Transport Pumps

Returns calcium ions to SR after contraction

Forcefulness

Factor that depends on length of sarcomeres before the contraction

Maximum Tension

Optimal zone of overlap between thick and thin filaments

Twitch Contraction

Brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron

Latent Period

Bried delay that occurs between application of stimulus and beginning of contraction, about 2 msecs

Relaxation Period

Period after contraction where calcium is returning to SR, 10-100 msecs

Refractory Period

Temporary loss of excitability after stimulation, duration varies

Recruitment

Process of increasing the number of active motor units to prevent fatigue and provide smooth muscular contractions

Concentric Isotonic Contraction

Contraction in which the muscle shortens

Eccentric Isotonic Contractions

Contraction in which the overall length of the muscle increases

Isometric Contraction

Contraction in which there is tension with no change in the length of the muscle