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