Graded Responses

How can graded responses be produced?

-Changing the frequency of muscle stimulation -Changing the number of muscle cells being stimulated

Types of graded responses

-Twitch -Summing of contractions -Unfused(incomplete) tetanus -Fused(complete) tetanus

What is the "all or have none" law in muscle physiology?

Applies only to the contraction of the muscle cell and not the contraction of the muscle as a whole -A muscle cell can either be fully contracted or not at all -can not be partially contracted -A whole muscle can be partially contracted, if only some fibers are contracted

Graded Responses

Different degrees of skeletal muscle shortening

Fused(complete) tetanus

Muscle stimulation is so rapid that no evidence of relaxation is visible and the contraction is completely smooth and sustained Frequency of stimulation doesn't allow for relaxation between contractions

Twitch

Single brief jerky contraction and relaxation Not how muscle normally operates

Unfused(incomplete) tetanus

Some relaxation occurs between contractions but the nerves stiumli arrives at an even faster rate than summing of contractions Unless the contraction is smooth and sustained it is unfused tetanus See additive effect More frequent stimuli unfused because their are dips due to relaxation, but not relaxation all the way to original resting state

What changes the force of a muscle contraction?

The force of a muscle depends on the number of muscle fibers stimulated -few muscle cells stimulated-contraction is small -many muscle cells stimulated-contraction bigger Contract more fibers cause greater muscle tension

Summing of contractions

When the delivery of nerve impulses to the muscle are so rapid that the muscle can't relax completely between the stimuli -effects of successive contractions are summed together and the contraction of the muscle gets smoother and stronger