KINE 1020 Lecture Notes - Lecture 21: Myocyte, Skeletal Muscle, Motor Unit
29 Mar 2016
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Type iia fast twitch: fatigue resistant (fr) Muscle fibers used for non-exertive movement (walking) Type iix (iib rat) fast twitch: fast fatiguing (ff) Muscle fibers used for powerful movements (jumping and sprinting) In order for a muscle to contract, there needs to be a stimulus (ap) that is followed by a response (contraction/force production). Contraction time ranges from 40-120msec: relaxation time ranges from 50-200msec, twitch response of a single muscle fiber can be slow or fast, the twitch time is dependent on the intrinsic properties of the muscles protein. What (else) determines the force generated by muscle : muscle length, ap frequency, number of fibres per motor unit & cross sectional area of each. Features of motor units: when activated - all muscle fibers within a mu contract, with only 1 mu activated weak contraction. Motor unit recruitment: mu size varies from one muscle to another.
