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

10. Fig 30.9A

11. Fig 30.9B

13. 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

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

15. Fig 30.10A

16. 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

17. 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

18. 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

19. Fig 30.10B

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

21. 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

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

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

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

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

28. 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

29. SPRAIN Symptoms: –pain, muscle spasm, muscle weakness, swelling, inflammation, cramping

31. TREATMENT REST ICE COMPRESSIO N ELEVATION