Outline-2, BIO 2310, Responses of Skeletal Muscle


A. Muscle twitch(100msec)

1. Latent period(10 msec)

Excitation-contraction coupling

2. Contraction period(40msec)


3. Relaxation period(50msec)

Returns to unstimulated tension/length

B. Graded contraction

1. All or none response

Refers to the myofiber

2. Multiple motor unit summation = Spatial

Individual motor units combine their activities to increase the contraction of the entire muscle.

3. Muscle tone

At any given time, some fibers are contracted which tightens muscle, but not enough to produce movement

4. Wave summation = Temporal

Summation in time, before complete relaxation

a. Incomplete tetanus

Contraction strength increases in amplitude with partial relaxation

b. Complete tetanus

Sustained contraction.

5. Asynchronous motor unit summation

Different motor units are activated at different times

6. Treppe

Stronger contractions after muscle has contracted several times. “Staircase” phenomenon

7. Isotonic & Isometric contractions

Isotonic – tension develops and it shortens

Isometric – tension develops and it doesn’t shorten