The Physiology of Muscle Contraction - WHOLE MUSCLE CONTRACTION: MOTOR UNIT SUMMATION Flashcards
What is a motor unit?
A nerve
cell and the group of
muscle fibers that it
causes to contract.
Whole muscle does not behave according to?
the All-or-None
Principle.
Do all the cells in a muscle contract when the muscle contracts?
Not always. Instead, only a few cells may contract.
What determines
the strength of the entire contraction?
The number of cells contracting in the muscle
What explains how one muscle can have
contractions of varying strengths: weak, medium, or strong?
Motor Unit Summation
Muscles can have contractions of varying strengths due to the presence of?
motor units
A motor unit is a group of muscle fibers whose contractions are all controlled by?
the same nerve cell (neuron).
How many nerve cells tells a group of muscle cells when to contract?
1 nerve cell
How many cells are in a motor unit?
1000 cells controlled by 1 nerve
Does the stimulus (above threshold) need to be stronger or weaker with the greater the number of motor units contracting in a muscle?
Stronger
Causes a graded response(stronger contraction) When the stimulus/electrical shock is increased.
Motor Unit Summation
What is the Effect of Threshold Stimulus?
An action potential is created in only
one neuron. Thus, all the fibers of that neuron’s motor unit contract. (Only one motor unit contracts out of the many that make up the
whole muscle).
What is the Effect of Submaximal Stimulus?
More and more motor units contract within the muscle, producing more and more forceful contractions.
What is Effect of Maximal Stimulus?
All motor units of the muscle are contracting. Thus, the muscle is contracting to its full extent.
What is Effect of Supramaximal Stimulus?
Contraction strength is the same as with a maximal stimulus.
