Lab Assignment 2: muscle mechanics Flashcards
wave summation
multiple stimuli cause a summed contraction - max = tetanic contraction
what does it mean when a muscle is tetanized
stimulus frequency is high enough to produce a sustained contraction
what is a tetanizing frequency
minimal frequency of stimulation required to produce a sustained contraction
what is a twitch
a contraction from a single stimulus – may be stronger or weaker depending on how many motor units the stimulus activates
T/F a single supramaximal stimulus will evoke a twitch contraction of max amplitude
true
a twitch is from a single stimulus (no wave summation)
T/F wave summation occurs because the second stimulus activates more motor units
false
1 supramaximal stimulus can activate all motor units on its own. wave summation is do longer length/strength of contraction - second stimulus keeps more Ca++ channels open and for longer
how long is a refractory period?
a few μs
T/F tetanic contraction produces greater tension than single twitch because more motor units are activated
false
all motor units may be activated in a single supra maximal stimulus twitch
tetanic tension is possible with multiple stimuli because the muscle is active for more time to overcome elastic components
T/F tetanic contractions are only important when we perform sustained muscle activity
false
a short contraction can be tetanic
T/F passive tension is the tension of a flaccid muscle
false
passive tension is the tension of the parallel elastic elements when stretched
T/F flaccid length is the length of resting muscle
false
flaccid length is excised muscle (no tension)
rest length is usually where active tension is greatest (usually slightly stretched)
explain the action of curare
blocks N1 cholinergic receptors (on skeletal muscle end plates)
