muscular system

the muscular system

the muscular system is the system involved in enabling your body to move.

types of muscle tissue

cardiac

cardiac muscle is the muscle in your heart that pump blood.
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smooth

smooth muscle is the muscle in hollow organs that make the organs contract.
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skeletal

skeletal muscles are the muscles that make us move. they attach to the bone.

skeletal contraction steps

  1. A nerve impulse travels down and axon and causes the release of acetylcholine.
  2. Acetylecholine causes the impulse to spread across the surface of the sarcolemma
  3. the nerve impulse enters the T Tubules and Sarcoplasmic Reticulum, stimulating the release of calcium ions
  4. Calcium ions combine with Troponin, shifting troponin and exposing the myosin binding sites on the actin
  5. ATP breaks down ADP + P. The released energy activates the myosin cross bridges and results in the sliding of thin actin myofilament past the thick myosin myofilaments
  6. The sliding of the myofilaments draws the Z lines towards each other, the sarcomere shortens, the muscle fibers contract and therefore muscle contracts
  7. ACh is inactivated by Acetylcholinesterase, inhibiting the nerve impulse conduction across the sarcolemma.
  8. Nerve impulse is inhibited, calcium ions are actively transported back into the Sarcoplasmic Reticulum, using the energy from the earlier ATP breakdown
  9. The low calcium concentration causes the myosin cross bridges to separate from the think actin myofilaments and the actin myofilaments return to their relaxed position.
  10. Sarcomeres return to their resting lengths, muscle fibers relax and the muscle relaxes.
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sarcomere

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disorders

muscular dystrophy

muscular dystrophy is the progressive weakening of the muscles. symptoms normally show between the ages of 2-3. they may include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, walking on the toes, large calf muscles, muscle pain and stiffness, and learning disabilities. the prevalence of muscular dystrophy is not exactly know but it is estimated that 1/5,600-7,700 males have it. there is no cure but therapy and medication can slow it.

tendonitis

tendonitis is a condition in which the tissue connecting muscle to bone becomes inflamed. symptoms include stiffness, swelling, tenderness, and weakness. the prevalence of tendonitis increases with age. tendonitis does not normally need treatment but can, and the treatment options include therapy, painkillers, dietary supplements, an icepack, or just simply resting it.