Muscle mechanics

By- Anshika Singh
(BPT 1st year)

1. Muscle mechanics ~ Anshika Singh

2. Muscle (joint) – contribute mobility and stability. Muscle controls mobility by controlling the movement of bony lever around joint axis. Give stability by reducing extraneous movement of joint surface and joint segments. Without muscle function, body is incapable of of either supporting itself against gravity or producing motion. Human movement is complex interaction of muscle function and joint lever system undar the control of the nervous system. Muscle structure contains contractile proteins within each muscle fibre to the organization of the fibre in the entire muscle.

3. Elements of muscle structure Muscle tissue i.e., contractile. Connective tissue i.e., non contractile. Muscle tissue which has the ability to develop tension in response to chemical, electrical or mechanical stimuli. Connective tissue which develop tissue tension in response to passive loading.

4. Composition of muscle fiber Contractile protein Structural protein

5. Contractile protein These protein mediate sliding of contractile fibers of cell’s cytoskeleton and of cardiac and skeletol muscle. Two types- Myosin (structural rigidity and movement) Actin ( network) These fibres are myofilaments.

6. Structural proteins These are the most abundant class of proteins in nature. Collagen is recognized as the most abundant mammalian protein. Structural proteins such as collagen fibronectin and laminin are utilized in cell culture application as attachment factors. These proteins maintain cell shape by composing structural elements in connective tissue like cartilage and bones in vertebrates. These proteins gives mechanical support to the body.

7. Contractile unit Sarcomere is the contractile unit of muscle. Each sarcomere is composed of two main protein filaments – actin and myosin which are the active structures responsible for muscular contraction. Z disc located at regular intervals along myofibril . Portion of sarcomere that extends over both the length of the thick filaments and a small portion of the thin filaments is called the anisotropic or A band.

8. Areas include only actin filaments are called isotropic or I band. Isotropic- anisotropic refers to the behavior of these portion of fibers when lights shines on them. H-zone – central area where there is no overlap with thin A band. M-line – central portion of H zone, which consist of the wide middle portion of thick filaments.

9. Cross Bridge Interaction It states that actin any myosin form a protein complex ( called actomyosin) by attachment of the myosin head on the actin filaments, thereby forming a sort of cross between the two filament. Initiated by interaction of thick and thin filaments within each sarcomere. Initiated by arrival of nerve impulse at the motor end plate (neuromuscular junction), which evokes an electrical impulse or action potential that travels along the muscle fiber.

10. Action potential initiates the release of calcium ions cause troponin to reposition the tropomyosin molecules so that receptor sites on the actin are free and the read groups of the myosin can bind with actin. Tension in sarcomere is generated with hydrolysis of ATP and release of ADP from myosin.

11. Types of muscle contraction 1. Concentric/ Shortening contraction 2. Eccentric/ Lengthening contraction 3. Isometric contraction

12. Isometric Length – Tension Relationship The force of tension that a muscle exerts varies with the length at which it is held and stimulated. Maximal tension is produced when the muscle fibre is approximately at its “ slack” or resting length. If the fiber is held at shorter lengths the tension falls off slowly at first and then rapidly. If the fiber is is lengthened beyond the resting length, tension progressively decreases.

13. The change I tension when the fiber is stretched or shortened primarily are caused by structural alterations in the sarcomere. Maximal isometric tension can be exerted when the sarcomere are at their resting length(2.0-2.5 micro meter), because the active any filaments overlap during their entire length and the number of cross bridge is maximal. If the sarcomere are lengthened, there are fewer junctions between the filaments and the active tension decreases. At sarcomere length 3.6 micro meter there is no overlap and hence no active tension.

14. Thank you