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Muscle Contraction and Movement

Muscle Contraction and Movement. Fig 30.7. Muscles. Muscles are attached to bones by tendons Muscles work in antagonistic pairs Ex. Biceps and triceps One muscle contracts while the other relaxes. Contractile apparatus. Skeletal muscle

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Muscle Contraction and Movement

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  1. Muscle Contraction and Movement

  2. Fig 30.7

  3. Muscles • Muscles are attached to bones by tendons • Muscles work in antagonistic pairs • Ex. Biceps and triceps • One muscle contracts while the other relaxes

  4. Contractile apparatus • Skeletal muscle • Muscle cell = muscle fiber (a single cell with one nucleus) • Muscle fibers are made of myofibrils (striated) • Myofibrils are made of units called sarcomeres • Sarcomeres are made of thick and thin filaments • Z line is the end of the sarcomere • Thick and thin filaments slide over one another to shorten the muscle during contraction

  5. Fig

  6. Fig 30.8

  7. Fig 30.9A

  8. Sliding filament theory • Links the structure of a sarcomere to its function • During contraction thin filaments slide over thick filaments • Thick filaments= myosin and have “heads” • Thin filaments = actin, these slide • Ca and ATP required for sliding and attachment

  9. Fig 30.9A

  10. Fig 30.9B

  11. Sliding filament theory • ATP binds to a myosin head, which is released from an actin filament • Hydrolysis of ATP cocks the myosin head • The myosin head attaches to an actin binding site with the help of Calcium • The power stroke slides the thin filament when ADP and P are released from it

  12. Sliding filament theory • 350 myosin heads per thick filament • Can bind and unbind to thin filament up to 5 times per second

  13. Fig 30.10A

  14. Motor neurons and muscle contraction • Motor neurons stimulate muscle contraction • Motor neurons are branched and can stimulate more than one muscle fiber • Motor unit = motor unit and all the muscle fibers it controls • Neuromuscular junctions = the synapse between a motor neuron and a muscle fiber

  15. Motor neurons and muscle contraction • The strength of a muscular contraction is controlled by the number of motor units activated. More motor units = stronger contractions • Muscles requiring precise control have one motor neuron per muscle fiber

  16. Motor neurons and muscle contraction • Mechanism of stimulation: • An action potential releases acetylcholine into the neuromuscular junction • Acetylcholine depolarizes the muscle cell channels inside on the sacroplasmic reticulum release Ca so it can reach the contractile apparatus • Mechanism of relaxation • Motor neuron stops firing • Ca pumped back into the SR

  17. Fig 30.10B

  18. https://www.youtube.com/watch?v=4201SrN0WlY

  19. MUSCLE INJURY • Muscle damage can be in the form of tearing (part or all) of the muscle fibers and the tendons attached to the muscle • The tearing of the muscle can also damage small blood vessels, causing local bleeding and pain

  20. You can put pressure on muscles during the course of normal daily activities, with sudden heavy lifting, during sports or work tasks

  21. MUSCLE STRAINS • When the muscle is overstretched or partially torn • Symptoms: • pain, tightness, swelling, tenderness, inability to move the muscle very well

  22. MUSCLE TEAR • A complete tear in the muscle • Symptoms: • pain, tightness, swelling, bruising, tenderness, immobility

  23. SPRAIN • An injury of a muscle and/or tendon • tendons are fibrous cords of tissues that attach muscles to bone

  24. SPRAIN • Caused by a direct or indirect trauma that knocks a joint out of position, and over stretches and ruptures supporting ligaments • Landing on an outstretched arm, sliding into a base, jumping and landing on the side of the foot, running on uneven surface

  25. SPRAIN • Symptoms: • pain, muscle spasm, muscle weakness, swelling, inflammation, cramping

  26. TREATMENT • REST • ICE • COMPRESSION • ELEVATION

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