Skeletal + Muscular Systems


The Skeleton

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Synovial Joint

Ball + Socket - ball shaped head articulates with cup shaped socket to give wide range of motion e.g. hip + shoulder

Hinge - cyndrical bone articulates with trough shaped bone so motion limited to one plain e.g. elbow, knee + ankle

Condyloid - similar to B+S but flatter bones allow motion in two planes e.g. wrist joint

Features of synovial joints:

  • ligament - tissue joins bone to bone + stabilises joint during movement
  • synovial fluid - lubricates + nourishes joint to protect it
  • articular cartilage - smooth tissue acts as shock absorber to protect joint
  • bursa - sack of synovial fluid preventing friction to protect joint
  • joint capsule - split into synovial membrane + fibrous capsule to protect them
  • pad of fat - small collection of fat cells cushion joint
  • tendons - join muscle to bone to stabilise them
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Types of Movement

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Planes of Movement

S(v)agital Plane - divides left + right e.g. plantar flexion, dorsiflexion, extension + flexion

Horizontal Plane - divides top + bottom e.g. horizontal flexion + horizontal extension

Frontal Plane - divides front + back e.g. abduction + adduction

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Muscular System

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Role of Muscles

Agonist - muscle directly responsible for movement at joint

Antagonist - muscle that has action opposite to agonist and helps in production of coordinated movement

Fixator - muscle that works with antagonist in creating effective movement by stabilising bones

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Types of Muscular Contraction

Concentric - muscle shortens, producing tension + bringing the two bones together e.g. in upward phase of bicep curl biceps brachii concentrically contract to lift weight

Eccentric -  muscle lengthens producing tension that resists forces such as gravity e.g. downward phase of bicep curl biceps brachii eccentrically contract to lower weight with control

Isometric contraction - when muscle contracts but doesn't change length e.g. biceps brachii holding free weight still

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Motor Units

Made up of motor neuron + muscle fibre it stimulates

Carries nerve impulses from brain + spinal cord to muscle fibres

1. Nerve impulse initiated by brain to contract rectus femoris

2. Nerve impulse travels down spinal cord into motor neuron

3. Nerve impulse travels down motor neuron into axon by action potential

4. When impuse reaches synaptic cleft, a neurotransmitter called Ach released

5. if action potential big enough + sufficient Ach, the impulse will travel across synapse + rectus femoris will contract

Uses all or none principle as all muscle fibres will give complete contraction or no contraction at all

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Muscle Fibre Types

Type 1:

  • (slow oxidative)
  • predominantly used for aerobic events e.g. marathon
  • recovery - quick recovery (within 90s)

Type 2a:

  • (fast oxidative glycotic):
  • predominantly for mixed aerobic/anaerobic events e.g. 1500m

Type 2b:

  • (fast glycotic)
  • predominantly used for power events e.g. 100m
  • recovery - take longer to recover (4-10 days if reach exhaustion)
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Movement Table

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