Filaments and Fatigue Flashcards
Muscle tension
force created by muscle
load
weight (force/ resistance) that opposes contraction
contraction
creation of tension in muscle by sacromere shortening
relaxation
release of tension in muscle
twitch
a single contraction-relaxation cycle
What are the 3 steps leading u to muscle contraction
events at neuromuscular junction, excitation-contraction coupling, and contraction-relaxation cycle
Latent Period (in reference to contraction)
contraction has not yet begun
Why is the contraction of skeletal muscle later than the action potential?
because it takes time for calcium levels to rise
How do muscle twitches differ from action potentials
because they can summate and do not have a refractory period
define a single twitch (time-tension relationships)
muscle relaxes completely between stimuli
Define summation (time-tension relationships)
stimuli closer together do not allow muscle to relax fully
If we space excitation closer in time, how does this affect the tension of the muscle twitch
our tension would increase
Ways we can increase force/muscle tension? (4)
stimulate more motor units, stimulate larger motor units, stimulate more fast twitch fibers, stimulate fibers faster and closer together (summation=greater force)
Tetanus
high rate of stimulation (sustained muscle contraction from sustained stimulus)
Unfused tetanus
stimuli are far enough apart to allow muscle to relax slightly between stimuli; near max contraction (not quite there), you can still see little bits of contraction and relaxation
Complete (fused) tetanus
steady tension (w/o relaxation), but then fatigue causes muscle to lose tension despite continuing stimuli (completely max out our contraction)
in skeletal muscle, what pump primarily gets rid of calcium?
SERCA pump
Where is the SERCA pump located in the skeletal muscle and cardiac muscle?
sarcoplasmic reticulum
Depletion Theory
if we run out of ATP, glycogen, or phosphocreatin we cannot have a contraction
isometric contraction
contractions create force without moving the load
isotonic contractions
create force and move load
describe the sacromeres and the elastic elements in isometric contraction
sarcomeres shorten while the elastic elements stretch (that is why there is little change in overall length)
isotonic concentric action is…
a shortening action (bringing a weight toward your body)
the isotonic eccentric action is…
the lengthening action (bringing a weight away from your body)
Nebulin
helps align actin
Titin
provides elasticity and stabilizes myosin to the Z disk (springy and it is an elastic element)
spindles do what (reflex arc)
respond to stretch
When we have a length-tension graph, why is it that the most decreased length has 0 tension (force)?
because it is maximally contracted, there are portions of actin that do not have a myosin partner and actin is also blocking other regions of actin; therefore, due to all these factors it cannot contract (= 0 force)
When we have a length-tension graph, why is it that the most increased length has 0 tension (force)?
because we maximally expanded it; myosin cannot grab the actin, so the muscle cell cannot contract
