Skeletal Muscle Contraction

Front 1

Define Contractility

Back 1

Capacity of MS fiber to undego shortening and change shape, becoming thicker

Front 2

Sarcomeres

Back 2

These sections shorten and become thick because the Actin filaments move toward the center this is constitues contraction

Front 3

Cross Bridges

Back 3

Myosin extensions that latch on to Actin and pulls them toward the center, shortening the Sarcomeres

Front 4

ATP

Back 4

-Energy needed to pull Actin strands together
-Require oxygen and glucose

Front 5

Sliding Filament Theory

Back 5

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.

Front 6

Stimulus for MS Contraction

Back 6

-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)

Front 7

2 Events of Relaxation

Back 7

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

Front 8

Threshold Stimulus

Back 8

Required stimuli for MS respond.
**Usually enought acetylcholine to reach a threashold stimuli is avail

Front 9

"All or None"

Back 9

When MS gets threshold stimui it will respond to its fullest extent
**Increased stimuli will not affect a stronger MS response

Front 10

Twitch

Back 10

A single contraction lasting a fraction of a second when some motor units are stimulated

Front 11

Fast Twitch Fibers

Back 11

-Power fibers
-Prone to Fatigue
-Develope bigger in diameter MS

Front 12

Slow Twitch Fibers

Back 12

-Endurance fibers
-Fatigue resistant
-Develop more capallaries

Front 13

TETANIC or TETANUS

Back 13

-Sustained contraction lacking even partial relaxation
-Spasm, like lockjaw

Front 14

Recruitment

Back 14

All Motor units are activated and MS fibers are stimulated..."all or none"

Front 15

Sustained Contraction

Back 15

Recruitment (firing of MS)
Summation (series twitching)
acting together

Front 16

Muscle Tone

Back 16

Appear at rest, but some sustained contraction is happening: posture

Front 17

Tonus

Back 17

Maintenance of tone due to the action of the nervous system keeping MS in a constant state of readiness

Front 18

Isotonic

Back 18

-Develop tension
-To cause or control joint movement
-dynamic contractions: varying degrees of tension change joint angles

Front 19

Isometric

Back 19

Iso=same
Metric=length
-no change in MS length but there's increase in MS tension

Front 20

2 types of Isotonic contractions

Back 20

1) Concentric: shortening of MS
2) Eccentric: No shortening of MS, but lengthening with control, which creats tension

Front 21

Passive

Back 21

Joint angle changes without MS contraction