1 / 23

Skeletal Muscle II

There are two artificial conditions under which the performance of muscle tissues can be studied: isotonic (constant tension) and isometric (constant length)In an isotonic contraction, the muscle supports the load at all times and is free to lift it the load determines the tension the experimente

lilike
Download Presentation

Skeletal Muscle II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Skeletal Muscle II

    4. Some definitions Work = load X distance; work = 0 if load is zero or contraction is isometric Power=Work/Unit Time; Power =zero if work=zero Therefore, work is some function of load and there must be some load at which power output is maximal. At this load, muscle performance is optimal.

    5. As load is increased, instantaneous shortening velocity decreases

    7. Mammalian skeletal muscle fibers can be divided into classes based on:

    8. Classification of vertebrate fiber types: features to consider Vmax Myosin ATPase activity Fatigue resistance Oxidative capacity Glycolytic capacity Fiber diameter Force/cross-sectional area

    9. Type I Vmax slow Myosin ATPase activity low a slow myosin is expressed Fatigue resistance high Oxidative capacity high Glycolytic capacity low Adapted for sustained , low intensity use

    10. What features go along with a high oxidative capacity? Mitochondria numerous Myoglobin abundant Oxygen and fuel are delivered at a rate that matches the demand - this is an open system during exercise, so Capillaries numerous. Fiber diameter small- because final delivery of fuel and gas transport within the cell are by diffusion.

    11. Type IIb Vmax fast Myosin ATPase activity high a fast myosin is expressed Fatigue resistance low Oxidative capacity low Glycolytic capacity high Adapted for brief, high intensity use

    12. What features go along with a high glycolytic capacity? Glycolysis is able to outrun the ability of the circulatory system to deliver fuel - this muscle becomes a closed system during exercise. Consequently there must be an abundant store of glycogen within the cells; exhaustion of the glycogen is a source of fatigue. Gas exchange is unnecessary to sustain contraction For these two reasons, the diameter of type II fibers can be large and capillaries can be sparse.

    13. What determines the maximum force of a muscle? Maximum force is obtained when all crossbridges are engaged, and the number of crossbridges is directly related to the cross-sectional area of the muscle, so the greater the cross-sectional area of a muscle, the greater its maximum force. The maximum force/cross-sectional area is similar for all muscle types.

    14. Sometimes a compromise is needed Some activities require both rapid movement and fatigue resistance For example flying - for birds that migrate over long distances swimming - for predatory fish that have a high cruising speed For these activities, the Type IIa fibers have evolved.

    15. Type IIa Vmax fast Myosin ATPase activity high a mixture of fast and slow myosins is expressed Fatigue resistance intermediate Oxidative capacity high Glycolytic capacity intermediate Fiber diameter intermediate Adapted for: sustained high-intensity exercise

More Related