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Muscular physiology (2)
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Muscular physiology (2)

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  • 1. (17) Muscle physiology is the study of muscle function. A muscle is a bundle of fibers that contract to produce heat, posture, and motion, either of internal organs or of the organism itself. Muscle physiology studies the physical, mechanical, and biochemical aspects of muscles in development, fiber structure, muscle structure, contraction, and strength- building. (1)
  • 2. (17)How do skeletal muscles providemovement, heat, and posture.Are all of these functions uniqueto muscles?Since skeletal muscles are attached to thebones of the body and they are undervoluntary control. The provide movement ofthe joints by contracting, also they preventfrom unwanted movement. To cause theskeletal muscles to contract, impulses aretransmitted by a nerve signal, called a motorneuron, which sends the impulse throughoutmultiple muscle cells to contract that muscleto produce movement.The chemical reactions that cause musclecontraction generate heat - energyconversion always generates "useless"energy; entropy increases (2)
  • 3. The characteristics are shared with the nervous system. The muscle impulse reaches the sarcoplasmic reticulum, which releases calcium ions into the sarcoplasm of the muscle fiber;Calcium binds to troponin, movingtropomyosin and exposing myosin binding sites on actin filament; Cross-bridges (linkages) form between actin and myosin; Actin filaments arepulled inward by myosin cross-bridges;The muscle fiber shortens as contraction occurs. (4)
  • 4. Muscle contractions occur every time wemove. The muscle must contract in order More muscleto move the bone that it is attached toor to provide resistance against a force.Isometric contractions occur when the info!muscle contracts but there is nomovement. Muscle contractions which (17)result in movement are known asisotonic contractions. There are twotypes of isotonic muscle contractionConcentric and Eccentric. Concentricmuscle contractions are the mostcommon form of contraction. These occurwhen the muscle shortens in length inorder to make the bone move. Thesecontractions occur when the body isworking against gravity. Eccentriccontractions are the opposite ofconcentric contractions. The musclecontracts but increases in length. Thistype of contraction occurs usually in thedirection of gravity, to control amovement. (5)
  • 5. (17) 3)Explain how the structure of the myofilaments is related to their function. Myofilament is a term that the chains of (primarily) actin and myosin that pack a muscle fiber. These are the force generating structures. Although there are still gaps in what we know of the structure and functional significance of the myofilament lattice, some of the key proteins includes myosin, actin, troponin, titin, and nebulin. a myofilament shows several distict bands, each of which hasbeen given a special letter. The lightest (least electron dense) band is known as the I band and consists mostly of actin. The wide, dark band, known as the A band, iscomposed primarily of myosin. In the center of the I band is an electron dense line, known as the Z-line. In the middle of the A band is another dense line known as the M line. (6)
  • 6. (17) In cross section, under very high magnification, both A and I bands can be seen to be hexagonal networks. These networks are apparently ordered and fixed at the M- and Z-lines. In the region where the A and I bands overlap (sometimes known as the H band) the two hexagonal networks intermesh so that each myosin filament is surrounded by six actin filaments. These networks appear to be anchored to (and through) the cell membrane in two ways. At the ends of fibrils, special structures anchor the terminal actin filaments to the membrane. There also appear to be connections between the Z and M lines and the cell membrane. (7)
  • 7. (17) 8)
  • 8. (17) 5)Explain how the sliding filament theoryallows for the shortening of a muscle fiber.Sliding filament theory in its simplestform states that muscle fibers shortenwhen actin filaments slide inward onmyosin filaments - pulling the z-linescloser together. Actin filaments (thelight bands in the diagram above) slideover myosin filaments (the dark bands)the H-zone and I-band decrease.Myosin filaments contain tiny globularheads, called cross bridges at regularintervals. These cross bridges attach tothe actin filaments pulling on them tocreate movement. Each flexion of across bridge produces only a verysmall movement in the actin filamentso many cross bridges throughout themuscle must flex repeatedly andrapidly for any measurable movementto occur. (9)
  • 9. (17) 6. Compare and contrast the role of Ca++ in excitation, contraction, and relaxation of a muscle cell. An action potential in the muscle cell is what triggers muscle cell contraction. We have seen that calcium ions regulate whether or not contraction can occur. The action of Ca++ and is generated by for removal and the relaxation is taken up in 24th plate. A muscle contraction in response to a single nerve action potential is called a twitch contraction. A myogram, a graph of muscle strength (tension) with time. The latent period is the time required for the release of Ca2+. The contraction period represents the time during actual muscle contraction. The relaxation period is the time during which Ca2+ are returned to the sarcoplasmic reticulum by active transport.
  • 10. 10) explain the meaning of unit of combined cells Cardiac muscle combines as a syncytium, which is a unit of combined cells. They are self exciting which means they don’t need nerve impulses to contract. (12)(17)
  • 11. (16)
  • 12. (17) 11)What is rigor mortis Atp binds to the myosin heads releasing it from actin and making the muscle pliable. If no atp is available, myosin heads remain stuck to actin and the muscle becomes stiff. This is the rigidity of rigor mortis following death. (13)
  • 13. (17) 12)What are the 4 factors that influence the strength of muscle contractions? 1. The number of muscle fibers stimulated 2. The relative size of the fibers 3. Frequency of stimulation 4. The degree of muscle strength(14)13)What are the phases of a twitch contraction? What molecular events occur during each ofthese phases.muscle contraction in response to a single nerve action potential is called a twitchcontraction.1.The latent period is the time required for the release of Ca2+.2.The contraction period represents the time during actual muscle contraction.(14)
  • 14. (17) 3. The relaxation period is the time during which Ca2+ are returned to the sarcoplasmic reticulum by active transport. 4. The refractory period is the time immediately following a stimulus. This is thetime period when a muscle is contracting and therefore will not respond to a second stimulus. Since this is occurring at the sametime as the contraction, it does not appear on the myogram as a separate event. (15)
  • 15. (17) 14)How does the treppe effect relate to the warm-up exercises of athletes? The concept or phenomenon of "Treppe" occurs when a muscle contracts more forcefully after it has contracted a few times than when it first contracts. This is due to the fact that active muscles requireMuscles of the decreasing degrees of succeeding stimuli toface include: elicit maximal contractions. Returning todeppresor, our example of the second set of squatstemporalis, feeling easier than the first, during the first set there was insufficient warm-up, and theand levators second set felt easier because the first set actually served as a warm-up. The phenomenon in which the contraction strength of a muscle increases, due to increased Ca2+ availability and enzyme efficiency during the warm-up. (15)