4 Muscle Mechanics copy

4 Muscle Mechanics copy - MECHANICAL PROPERTIES OF WHOLE...

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MECHANICAL PROPERTIES OF WHOLE SKELETAL MUSCLE CELLS
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Mechanical Characteristics of a Whole Muscle 3 major mechanical variables: Force Initial Length Velocity
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The force put on an object by a contracting muscle is muscle TENSION The force put on a muscle by an object is LOAD .
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Muscle Twitch The mechanical response of a whole muscle to an electrical stimulation (single action potential) is a twitch .
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2 Types of muscle contraction 1. Isometric - Muscle is not allowed to shorten and produces force (tension) only. 2. Isotonic - Muscle allowed to shorten and the force (load) applied remains constant.
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Steps of a single Isometric muscle twitch: 1. Single action potential 2. Latent Period (E-C Coupling time) 3. Contraction Time (velocity of attaining maximum force. What does this depend on? Answer - Cross bridge cycling time and Ca-ATPase activity (how long Ca remains elevated)
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Steps of a single Isotonic muscle twitch: 1. Latent period 2. Shortening 3. Velocity of Shortening 4. Duration of twitch All of these things depend on the load the muscle is lifting while shortening. (more later on this. ... )
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Length Tension Curve Force is a Function of Initial Length If we put a length of skeletal muscle on a muscle lever and control its initial length and also do not allow it to shorten, Isometric Contraction, we can measure the force a muscle generates as a function of length .
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LENGTH - TENSION CURVE
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1. Rule - The amount of force generated is proportional to the number of cross-bridges binding.
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4 Muscle Mechanics copy - MECHANICAL PROPERTIES OF WHOLE...

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