Objective 13 Flashcards
How is a muscle twitch (the simplest contraction observable in a lab) recorded?
As a myogram
What is threshold stimulus?
The stimulus strength at which the first observable muscle contraction occurs
How does a muscle twitch (myogram) occur?
A muscle twitch occurs in response of a muscle to a single, brief threshold stimulus
Beyond threshold, how do muscles contract?
Beyond threshold, muscle contracts more vigorously as stimulus strength in increased
How is the force of a muscle contraction controlled?
by recruitment of motor units (multiple motor unit summation) which brings more and more muscle fibers into action
What is the size principle?
Motor units with sequentially larger fibers (greater diameter) are recruited as stimulus intensity increases
What is Treppe?
The Staircase Effect: increased response to multiple stimuli of the same strength
Graphically: looks like recruitment
Why do contractions increase in strength?
Because enzymes become more efficient because heat increases as muscle contracts
When muscles contract, there is an increase in the availability of Ca2+ in what location?
in the sarcoplasm
Why does a “warmed up muscle” perform better?
A “warmed up muscle” performs better because there is a subsequent increase in the availability of Ca2+ in the sarcoplasm
