Muscle Review

Topics: Myosin, Muscle, Muscular system Pages: 5 (1203 words) Published: April 4, 2013
Muscle Contraction
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1 What is meant by the skeletal system?
The skeletal system is charge of proving movement, protection, and support. In terms of the muscular system, the skeletal systems functions as a lever for muscles to work from. 2. How is technology tied to our understanding of classical muscle physiology? Technology can help scientists simulate different muscle contractions. 3. What are the four functional characteristics of muscle? * Elasticity - How well the muscle can return to its original form once it has been stretched or compressed. * Extensibility - The ability of a muscle group to be stretched to its starting position or beyond. * Contractitility - The ability to shorten.

* Excitability - A muscle’s ability to respond to stimulus. 4. What is the connective tissue sheath that surrounds a bundle of muscle fibers? Perimysium.
5. What is the connective tissue sheath that surrounds a whole muscle? Epimysium.
6. What is the connecting point between a nerve ending and skeletal muscle? Neuromuscular Junction.
7. What is the ion responsible for initiating muscle contraction? Calcium ions.
8. Electrical excitation moves deep into the muscle by passing along what structures? T-tublules?
9. Calcium is released from what structure within each muscle cell? Sarcoplasmic Reticulum.
10. An actin myofilament is actually composed of what three different molecules? * Troponin - When Calcium binds to troponin, it changes shape, which moves tropomyosin away. This uncovers the actin binding site, which allows myosin to bind to actin and begin contraction. * Tropomyosin - Covers the myosin binding sites on actin. * G-actin

11. Myosin molecules make contact with actin via what structure? Cross-bridges - The chemical bond myosin molecule forms with the actin molecule 12. What is the contractile unit of skeletal muscle?

Myofibrils - Makes up striated muscle fiber.
13. What is the difference between an A-band and an I-band? * A-band: A bands are the dark areas where myosin, and actin overlap. * I-band: I bands are the light areas that contain only actin. 14. What is the significance of the triad in muscle contraction? Once a triad has been reached, an action potential triggers the release of Ca2+ from the cisternae of the sarcoplasmic reticulum. This causes a reaction where Calcium ions binds to troponin, which helps set off the contraction. 15. Muscle contraction requires energy stored in what molecule? ATP.

16. What physiological events occur during the lag phase of muscle contraction? The action potential sweeps across the sarcolemma, and the sarcoplasmic reticulum releases calcium ions. The muscle fiber does not produce tension during the latent period, because the contraction cycle has yet to begin. 17. What is the difference between the contraction phase and the relaxation phase of muscle contraction? * Contraction phase: During contraction phase, cross-bridges become active (this generates tension). At this point, the muscle will either lengthen, shorten or remain the same. On a myogram, this is represented by the peaks. * Relaxation phase: Calcium levels drop, active sites get covered by tropomyosin, and cross-bridges are declining. 18. What is a threshold stimulus?

The minimal level of stimulus required to cause a muscle fibre to contract. 19. What is the...
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