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stimulation of a motor neuron
- 1. acetylchole is released
- 2. electrical impulse transmitted along T tubules
- 3. Calcium is released
- 4. Calcium binds to troponin C
- 5. Troponin-tropomyosin complex shifts position
- 6. myosin binding site is exposed
- 7. myosin heads form cross-bridges with actin. cross bridge cycling occurs.
- 8. actin filaments are pulled toward center of sacromere
- 9. calcium is pumped back into sarcoplasmic reticulum
- 10. muscle relaxation
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sarcomeres
- z disk to z disk
- z disk = attachment point for sarcomeres
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Is energy required for muscle activity?
- Yes, energy is required.
- ATP production is important!
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contraction
formation of cross-bridges between thick and thin filaments
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isometric
- same length
- muscle not allowed to shorten
- TENSION and FORCE is measured
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isotonic
- same strength (weight)
- muscle allowed to shorten
- DISTANCE SHORTENED is measured
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motor unit
somatic motor neuron and all the muscles it stimulates
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muscle tension
force exerted by a contracting muscle
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all-or-none principle
mucle cells always contract completely each time they are stimulated by their motor neuron, and they do not contract at all if they are not stimulated by a motor neuron
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muscle tone
intermediate level of force
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summation
accumulation of effects, especially those of muscular (or neural) activity
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tetanus
sustained maximal muscle contraction resulting from high frequency stimulation
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slow twitch
- slow, steady contractions; muscles used for posture
- do not fatigue easily
- use aerobic pathway to generate ATP
- many mitochondria to produce ATP
- well supplied with blood bringing needed oxygen
- high oxygen store (myoglobin) within the muscle
- myoglobin and numerous blood vessels give muscle reddish color; "red" meat
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fast twitch
- quick, powerful bursts of energy; muscles used by sprinters
- fatigue easily
- use anaerobic pathway (glycolysis) to generate ATP
- few mitochondria to produce ATP
- not supplied with much blood
- low myoglobin concentrated with muscle cells
- sometimes referred to as "white" meat
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strength training
- resistance training
- short, intence
- builds more fast-twitch myofibrils
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aerobic training
- builds endurance
- increases blood supply to muscle cells
- reach target heart rate at least 20 minutes, three times a week
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skeletal muscle
voluntary (through somatic nervous system)
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Activation of cardiac and smooth muscles. Voluntary or Involuntary?
Involuntary
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Muscular Dystrophy
group of inherited muscle-destroying diseases. Duchenne's muscular dystrophy is due to lack of the protein dystrophin in the muscle cell.
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