1. Sliding Filament Theory
Muscle Structure and Function
Sliding Filament Theory
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4. Muscle Striations
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5. Components of skeletal muscle
d) myofibril
c) muscle fibre
b) muscle fibre bundle
a) Muscle belly
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6. How do muscles contract?

7. How do muscles contract?
The muscular system and the nervous system work together to signal and receive signals from the brain to allow for muscular contraction.
The link = neuromuscular junction

8. How do muscles contract?
A muscle contraction results from a signal from a nerve impulse.
The electrical impulse travels down the neuron and body of the nerve to the neuromuscular junction.
(Where the nervous system and the muscle meet)

9. Neuromuscular Junction
Axon
Neurotransmitter acetylcholine (Ach)
Sarcolemma
Axon Terminal
Synaptic Cleft
Receptor
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10. How do muscles contract?
Acetylcholine is released and receptors on the muscle fibers detect the chemicals presence and muscle contracts.
Within a motor unit (bundle of muscle fibers), all fibers contract at the same time or all fibers are relaxed = all or none principle

11. Neuromuscular Junction
Axon
Neurotransmitter acetylcholine (Ach)
Sarcolemma
Axon Terminal
Synaptic Cleft
Receptor
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12. The Motor Unit Dendrites Neuron cell body Axon hillock Motor neuron
Myelin sheath
Direction of action potential
Neurolemma
Neuromuscular junction
Terminal branches
Motor end plate
Muscle fibres
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13. How our muscle contracts once the message has been recieved
Sliding Filament Theory

14. Muscle Structure A muscle is a collection of many microscopic fibers.
Each muscle fiber consists of many small fibrils which are composed of even smaller protein filaments. (actin and myosin)
Myosin = thicker Actin = thinner
When a muscle contracts/shortens the finer/thinner actin filaments slide toward eachother and pass over the myosin filaments.

15. Longitudinal section of myofibril
(a) At rest
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16. Sliding Filament Theory
When a nerve impulse is received at the muscle (neuromuscular junction) it enters the interior of the fiber via a tuble.
The impulse causes the release of calcium ions (Ca++).
As a result, the myosin cross-bridges form a type of bond with selected sites on the actin filaments.

17. The Sliding Filament Theory
ATP is split and the energy released allows the acting filaments to slide toward each other. Consequently the muscle fiber shortens by about one third of its resting length.

18. The Sliding Filament Theory
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19. The Sliding Filament Theory
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20. The Sliding Filament Theory
Myosin crossbridges
Results in the sliding or overlap of the actin and myosin filaments
Causes sarcomere to contract (muscle contraction)
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21. Sliding Filament Theory
In relaxation phase, the effect of the nerve impulse subsides, calcium ions are removed and the bond between myosin crossbrides and the actin filaments is broken.

22. Beef Muscle Contraction
Video
Contraction and Relaxation of muscle
Beef Muscle Contraction

23. Contractile Machinery: Tendons, origin, insertion
In order for muscles to contract, they must be attached to the bones to create movement
Tendons: strong fibrous tissues at the ends of each muscle that attach muscle to bone
Origin: the point of attachment of the muscle to the bone that does not move
Insertion: the point of attachment of the muscle on the bone that moves
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24. Muscle Fibre Types Fast twitch fibres: Slow twitch fibres:
Slow Oxidative (Type I)
Fast twitch fibres:
Fast Glycolytic (Type IIa)
Fast Oxidative Glyc. (Type IIb)
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25. A. Slow Twitch Fibres
Suited for repeated contractions during activities requiring a force output of less than 20 to 25 percent of max force output
Examples: lower power activities, endurance events
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26. B) Fast Twitch Fibres
Significantly greater force and speed generating capability than slow twitch fibres
Well suited for activities involving high power
Examples: sprinting, jumping, throwing
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27. Relative involvement of muscle fibre types in sport events.
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28. Muscle Biopsy Fast Twitch (Type II Fibres) Capillary Blood Slow Twitch
Vessels
Slow Twitch
(Type I Fibres)
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29. Muscle Teamwork Agonist (prime mover): Antagonist: Synergist:
- Muscle or group of muscles producing a desired effect
Antagonist:
- Muscle or group of muscles opposing the action
Synergist:
- Muscles surrounding the joint being moved
Fixators:
- Muscle or group of muscles that steady joints closer to the body axis so the desired action can occur
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30. Bending or straightening of the elbow requires the coordinated interplay of the biceps and triceps muscles.
The triceps relaxes and the biceps contracts
The triceps contracts and the biceps relaxes
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31. Agonist and Antagonist Pairs