Muscle Contraction   Sliding Filament Theory

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Muscle Contraction Sliding Filament Theory

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1. Muscle Contraction – Sliding Filament Theory

2. Muscle contraction Muscles contraction can be placed into 2 categories; INVOLUNTARY e.g. blinking VOLUNTARY e.g. jumping Involuntary contractions take place automatically at ‘spinal cord level’ often without any actions / decision made by the brain. Voluntary contractions are caused by conscious decisions made by the brain to initiate movement. ESSENTIAL FOR SPORTS PERFORMANCE

3. Muscle contraction Muscles contraction caused by nerve impulses travelling down a MOTOR NERVE OR MOTOR AXON These impulses travel down the motor nerve to the muscle where the terminal is called a MOTOR END PLATE. This is also known as the NEUROMUSCULAR JUNCTION. When the impulse reaches this point it triggers the release of a transmitter substance.

4. Muscle contraction Task: Find out the differences between slow and fast twitch motor nerves and draw a structural diagram of each to highlight these. The SYNAPSE:

5. Muscle contraction The SYNAPSE: As the transmitter substance, ACETYLCHOLINE, reaches the post synaptic membrane it either stimulates the muscle or not depending on the amount of ACETYLCHOLINE released. This is known as the ALL OR NONE LAW If the impulse continues it is called a EXCITATORY POST SYNAPTIC ACTION POTENTIAL (E.P.S.P) and / or WAVE OF DEPOLORIZATION. These spread over the T-Tubules within the muscle cells and release Ca2+ ions which are needed to initiate muscle contractions.

6. Muscle contraction Muscle Structure: TASK: RESEARCH THE FOLLOWING STRUCTURES – MUSCLE BELLY, FASCICULUS, MYOFIBRIL and SARCOMERE. Made up from 2 types of protein known as MYOFILAMENTS; AcTin – (Remember the T stands for “thin” strand) Myosin CROSS BRIDGES are made between these 2 proteins filaments to create muscle tension and contraction These cross bridges occur on special BINDING SITES found on the ACTIN filaments.

7. Muscle contraction Muscle Structure:

8. Muscle contraction Muscle Structure: STRIATED FIBRE

9. Muscle contraction Muscle Structure:

10. Muscle contraction TASK: Visit and For further animated content on the sliding filament theory and many other physiological lessons.

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