what is the amount of tension refferring to
strength
what is the length tension relationship
the amount of tension (often recognized as strength) generated by a muscle depends on how stretched or shortened it was before it was stimulated
if overly shortened before stimulation
weak contraction
- thick filaments butt against z disc
if already too short, no distance to continue ging and therefore cntractin is weaker
if too stretched before stimulated
weak contraction
minimal overlap f thick and thin filaments= minimal cross bridge formation
optimum resting length
produces greatest force when muscle contracts
want zone of overlap to 20%
more interaction between a and m = stronger
what maintains muscle tone
the nervous system
to ensure that resting muscles are near this length
what is muscle tone
partial contraction
how long after death does rigor mortis set in
3-4 hours
hardening of muscles and stiffening of body after death
why does rigor mortis occur
deteriorating sarcoplasmic reiculum releases Ca
the sarcolemma (also deterorating) allows Ca to enter cytosol
Ca acivates crossbridges
muscle contracts and cannot relax because no ATP to undo
what allows muscle relaxation in rigor mortis
myofilaments begin to decay = relax
what is the time period of rigor morits
peaks at 12 hours after death
stays for 48=60 hours
what is a muscle twitch
a muscle contraction
myogram
tracks excitation coupling
a chart of the timing and strength of a muscle’s contraction
define twitfch
a quick cycle of contraction and relaxation when stimulus is at threshold
entire twitch lasts 7-100 msec dependnig on the muscle fibers involved
latent period
very brief delay between stimulus and contraction
!! the time required for excitation, excitation coupling, and tensing of elastic components f muscle
subthreshld stimuli
no cntractin at all
but tension develops
at threshold activity
twitch produced
what other stimuli can cause twitch strength to vary ( despite the voltage delievered)
- the muscles starting length
- muscles fatigue with cont use
- warmer muscles= quicker enzymes
- hydration level = dehydration = hard to move
- frequency of stimulus
increase it and will increase tension output
isometric muscle contraction
holding in place
muscle has tension but does not shorten!
muscle produces internal tension but external resistance causes it to stay the same length
can be prelude to mvmt when tesnion is absorbed by elatic copmonent of muslce
important in posutral muscle function and anatgonistic muscle joint stabilization
isotonic muscle contraction
muscle changes length with no change in tension- allows you to slowly increase length and decrease tension (set a cup down)
concentric contraction
isotonic muscle contractionwhere muscle shortens as it maintains tension
liftign weights
eccentric contraction
isotonic muscle contraction
muscle length increases as it maintains tension
ex: lowering weight
