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VCE PE Units 1 & 2 Neuromusculoskeletal System Muscle formation, recruitment and contraction. Key Knowledge and skills. Learning Intentions. Strengthen your understanding of the musculoskeletal system To learn the characteristics of a motor unit including how it is controlled. - PowerPoint PPT Presentation
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VCE PE Units 1 & 2Neuromusculoskeletal System
Muscle formation, recruitment and contraction
Key Knowledge and skillsKEY KNOWLEDGE KEY SKILLS
The way the neuromuscular and musculoskeletal systems work together to bring about movements including major bones, muscles, joints and joint action
The various characteristics of the different muscle types – fibre and arrangement
Isotonic, isokinetic and isometric muscle contractions
The agonist and antagonist relationship as related to reciprocal inhibition and the associated use of stabilisers
The nervous control of muscles including recruitment of motor units, fibres and types of contraction
Correct use of anatomical terms related to major bones, muscles, common joints and their actions that bring about movements.
Participate in and analyse a broad range of movements used in sporting activities and be able to identify key bones, muscles and joint movements associated with those movements.
Explain and discuss how reciprocal inhibition works
Identify the different types of muscle fibres and contractions responsible for a wide range of physical activities performed at varied intensities
Learning Intentions
• Strengthen your understanding of the musculoskeletal system
• To learn the characteristics of a motor unit including how it is controlled
Muscle fibre arrangementFusiform- Run longitudinally with the tendon. E.g. Biceps in the armProduce low force but can shorten over a long range
Penniform- run at angles to tendon.Can produce greater force with a higher number of fibersDivided into 3 groups:
• Unipennate (fibers branch out to one side of the tendon)E.g. Gastrocnemius• Bipennate (Fibers branch out to both sides of the central tendon)E.g. Quadriceps• Multipennate (fibers branch out repeatedly from a number of tendons)E.g. Deltoid
Muscle fibre arrangementUsing what you have learnt, label the following muscle fibre types
ANSWERS….
Complete text book ‘Thinking Things Through’ Page 16
Questions 1-4
The microscopic structure of muscles
Neuromuscular Junction
A single muscle contraction is initiated by an electrical signal in the CNS (Central Nervous System) that is transmitted along a threadlike axon of a motor unit to a group of skeletal muscle fibres.when the signal reaches the end of a motor unit, it must cross a ‘gap’before it can stimulate the skeletal muscle fibre to contract.This “gap” is called the neuromuscular junction (NMJ).A chemical know as the neurotransmitter assists in carrying the Electrical signal across to the adjacent muscle fibre.
A momentary change in cell voltage then results in action potentials spreading across the skeletal muscle fibre which resultsin contraction and force production.A stronger stimulus will produce a greater number of action potentials per second and a stronger contraction.
Microscopic Structure of a Skeletal Muscle worksheet
Nervous control of muscular contractions
Motor neurons convey nerve impulses form the brain to muscles
A motor neuron and the fibres it controls/stimulates are known as the motor unit
Sensory neurons convey nerve impulses from muscles, organs and cells to the brain
The all or nothing principles states:
It is not until an electrical threshold is surpassed that all of the fibres linked to a motor unit will fire together and maximally.
Gross movements requiring major muscle involvement require more motor units than precise/ fine movements
Fibres will be recruited according to the activity demand and this is known as preferential recruitment
Sliding Filament Theory
*How muscles contract*Myofilaments sliding across each other
Steps:Electrical impulse sent from brain to the synapse of individual myofibrils[neuromuscular junction]Acetylcholine activates the release of calcium ions This stimulates oar-like projections call ‘Cross-bridges’ to reach out and attach to the actin filamentsCross bridges shorten and pull actin filaments towards the centerThe muscle contracts
http://youtu.be/xhgDbjrrmFg (SFT song)http://youtu.be/0kFmbrRJq4w
Sarcomere region
Muscle shortening
Muscle lengthening
A band Unchanged UnchangedI band Shortens LengthensH zone Shortens and
disappearsReappears and lengthens
Z line Unchanged Unchanged
The effect of muscle contraction on structures of the sarcomere
How muscles contract
Insert 1.23
Thinking Things ThroughPg. 22
Questions: 1,2,3,4,5
Types of ContractionThere are basically three types of muscular contraction, classified by the movement they cause. These are listed below in order of occurrence in everyday activity, from most common to least common:
• isotonic (concentric and eccentric)• isometric• isokinetic
lsotonic contractionOccurs whenever the muscle length changes through a range of motion or action. When a constant load (weight) is being moved, differences exist in the amount of force applied at various joint angles.Isometric contractionOccur when tension is developed but no change results in the length of the muscle. Isometric contractions hence involve little, if any, change in muscle length while tension is developed.lsokinetic contractionTension developed is maximal throughout the entire range of motion and is common on hydraulic fitness equipment. The amount of force applied by the machine always equals the amount of force applied by the muscle.
http://youtu.be/T3OiOJ6-x34 http://youtu.be/4qCaiaFwtL0
Fast & Slow Twitch FibresMuscles are made up of two different types of fibres:• Red, type I, slow-twitch fibres (ST), best suited to aerobic, endurance work such as triathlons.• White, type II, fast-twitch fibres (FT), best suited to short-duration, high intensity anaerobic work, for example the bursts of power and speed required to sprint.
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Thinking Things ThroughPg. 26
Questions:1-4
Fibre Recruitment TheoryRecruitment: The progressive activation of a muscle by consecutive activation of motor units
i.e. When the muscle is first activated, the earliest motor units to fire will be small in size with progressively larger units recruited as the strength of muscle contraction is increased.
To measure the neural activity of muscle you use anElectromyography (EMG). An EMG records both the quality andquantity of electrical activity within a muscle.
Factors Affecting Muscle Strength
• Fibre arrangement• Muscle fibre recruitment• Muscle fibre type• Speed of contraction• Gender• Age
LabMuscle cross-sectional area V.s strengthPg. 27
SAC revision
Practical- complete the worksheet
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