Sliding Filament Model
Sliding Filament Model
- In order to contract, actin and myosin filaments must move past each other.
- Myosin pulls actin inwards to centre of sarcomere resulting in:
- Light back becoming narrower.
- Z lines moving closer together.
- H zone becoming narrower.
- It is said to be contacting.
- Myosin pulls actin inwards to centre of sarcomere resulting in:
Structure of Myosin
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Structure of Actin
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How Muscle Contraction Occurs
- Muscle contraction is triggered when action potential arrives at a neuromuscular junction (where a motor neuron and skeletal muscle meet)
- Multiple neuromuscular junctions ensure all muscle fibres contract simultaneously.
- The more muscle fibres that are to be stimulated, the greater the impulse required.
Energy Supply During Muscle Contraction
- Large quantity of energy required for contraction is provided by hydrolysis of ATP into ADP and Pi, and is required for the movement of myosin heads and to allow reabsorption of calcium ion in sarcoplasmic reticulum.
- Aerobic Respiration
- Most ATP is regenerated from ADP during oxidative phosphorylation inside a mitochondria.
- Occurs during periods of long, low intensity exercise as oxygen is required.
- Anaerobic Respiration
- ATP is regenerated by glycolysis.
- As more oxygen is used than provided, pyruvate is converted into lactic acid resulting in muscle fatigue.
- Anaerobic respiration is used during short periods of high intensity exercise.
- Creatine Phosphate
- Creatine phosphate is a molecule which acts as a phosphate reserve, immediately available for regeneration of ATP.
- Reserve is used up quickly, and then replenished using phosphate using ATP.
- Used during short bursts of intense activity, eg a superman punch.
- Muscle fatigue is the long lasting reduction of the ability to contract and exert force, and can result in harm.
- Electrodes can be used to show electrical activity and track fatigue, producing an electromyogram.
- Electrical currents are created by contraction, changes in the signal which show fatigue are increased mean amplitude, decreased frequency and a disruption of pattern.
- Experiments into muscle fatigue involve tracking the effect of characteristic movements, for research into sport injuries, ergonomics etc.