PHILS Pre/Post Lab questions: Principles of Summation and Tetanus
What was the longest time interval between stimuli when summation was first observed?
About 210 ms
A contraction is produced by an increase in the level of calcium in the sarcoplasm. Where is calcium stored when the muscle is at rest?
in the sarcoplasmic reticulum
In a resting skeletal muscle, calcium is stored
in the sarcoplasmic reticulum
Why would the rate of muscle relaxation be slower after tetanus than after a single twitch?
it takes time for large amounts of calcium in the sarcoplasm to be taken up by the sarcoplasmic reticulum
An action potential in skeletal muscle fibers increases sarcoplasmic calcium levels because
it travels down the T-tubules, stimulating voltage-gated calcium channels in the sarcoplasmic reticulum membrane
During a single twitch contraction of a skeletal muscle fiber
maximum tension is never achieved
During incomplete tetanus, the amount of tension increases above that seen with a single twitch because
there is an accumulation of calcium in the sarcoplasm
Calcium initiates a contraction of skeletal muscle by binding with
troponin
What was the time interval between stimuli when single twitches were observed?
Greater than 250 ms
What was the longest time interval between stimuli when incomplete tetanus was first observed?
about 170 ms
What was the longest time interval between stimuli when complete tetanus was first observed?
about 70ms
During summation, the muscle contracted
and did not return to resting length before contracting again
During single twitch contractions, the muscle contracted
and returned to resting length before it contracted again
During incomplete tetanus, the muscle
contracted so that the single contractions created more tension than seen during single twitches
During complete tetanus, the muscle
produced a prolonged (fused) contraction, and single contractions could not be seen