Musculoskeletal

• Function of the skeleton:

  Blood cell production - red and white blood cells are produced in bone marrow.

  Protection - of vital organs.

  Movement - muscles attach to bones and form a lever system.

  Shape - forms a rigid framework.

  Mineral store - absorbs calcium from blood for bone production.
• Bones are made of calcium, they are spongy at the head ad compact at the shaft with growth plates at either end.

  Joints are where 2 or more bones articulate to create movement, can be fixed, hinge, ball and socket, pivot, condyloid or gliding.
• Ligament

  A tough band that is slightly elastic, they connect bone to bone and stabilise joints preventing dislocation
• Tendon

  A tough band of fibrous tissue that connects bone to muscle, it withstands tension and pulls on bone to cause movement
• Articular cartilage

  Smooth tissue that covers the surface of articulating bones, they absorb shock and allow friction free movement
• Joint capsule

  A fibrous sac with an inner synovial membrane that encloses and strengthens the joint, and secretes synovial fluid
• Bursa

  A closed fluid filled sac found where tendons rub over bones, it reduces friction between tendons and bones
• Planes of movement:

  Frontal plane, lies vertically and divides the body into anterior and posterior (front and back), abduction and adduction take place here.

  Sagittal plane, lies vertically and divides the body into left and right, flexion and extension take place here.

  Transverse plane, lies horizontally and divides the body into superior and inferior (top and bottom), horizontal flexion and horizontal extension take place here.
• Flexion

  Decreasing the angle between 2 bones, e.g elbow in preparation of shot put
• Extension


  Increasing the angle between 2 bones, e.g elbow in recovery of shot put
• Horizontal flexion

  The limb is parallel to the ground and the joint moves towards the midline of the body, e.g shoulder in recovery of discus
• Horizontal extension

  The limb is parallel to the ground and the joint moves away from the midline of the body, e.g shoulder in preparation of discus
• Adduction

  Moving a body part across/towards the midline of the body, e.g shoulder in down phase of star jump
• Abduction

  Moving a body part away from the midline of the body, e.g shoulder in up phase of star jump
• Circumduction

  Conical shape movement, e.g shoulder during front crawl
• Plantar flexion


  Ankle movement when toes are pointed, e.g ankle in execution of high jump
• Dorsi flexion

  Ankle movement when toes move towards the shin, e.g ankle in preparation of sprint start
• Medial/internal rotation

  Rotation towards the midline of the body across a longitudinal axis, e.g hip during the execution of plough stop
• Lateral/external rotation

  Rotation away from the midline of the body across a longitudinal axis, e.g hip when stopping a football with the inside of your foot
• Agonist is the prime mover, it shortens and it is responsible for creating movement.

  Antagonist is opposite the agonist, it relaxes and lengthens.

  Fixator stabilises the joint and helps the agonist function effectively.

  Antagonist pairs are as 1 muscle shortens the other lengthens.
• Isotonic contraction, tension in a muscle causes movement and it changes length.

  Concentric contraction, tension develops as muscle shortens, causing joint movement.

  Eccentric contraction, tension develops as muscle lengthens, it controls joint movement when against resistance.

  Isometric contraction, tension in muscle with no movement, it stays the same length and stops movement.
• During resistance work the agonist has eccentric contractions as it lengthens under tension to control the movement.

  E.g downward phase of a push up, the tricep brachii is the agonist which lengthens under tension with eccentric contraction.

  E.g downward phase of a bicep curl, the bicep brachii is the agonist which lengths under tension with eccentric contraction.
• Slow oxidative fibres:

  Recruited 1st, good for low intensity endurance exercise, e.g marathon runners.

  Structure - high myoglobin content, high mitochondrial density, high capillary density, small neurons, few fibres per neuron, low pc stores and low glycogen stores.

  Function - high fatigue resistance, high aerobic capacity, slow speed of contraction, low force of contraction and low anaerobic capacity.
• Fast oxidative glycolytic fibres:

  Recruited 2nd, good for speed endurance exercise, e.g 800m runners

  Structure - high capillary density, high pc stores, moderate myoglobin content, moderate mitochondrial density, moderate glycogen stores, many fibres per neuron and large neurons.

  Function - high force of contraction, fast speed of contraction, moderate fatigue resistance, moderate aerobic capacity and moderate anaerobic capacity.
• Fast glycolytic fibres:

  Recruited 3rd, good for high intensity explosive exercise, e.g 100m runner/shot put

  Structure - high glycogen stores, high pc stores, large neurons, many fibres per neuron, low myoglobin content, low mitochondrial density and low capillary density.

  Function - high anaerobic capacity, high force of contraction, fast speed of contraction, low fatigue resistance and low aerobic capacity.
• Motor unit

  A group of muscle fibres and a neuron, it carries nerve impulses from the CNS to muscle fibres initiating muscle contraction
• Motor neurone

  Specialised nerve cells that are made up of a cell body and extending axon that branches off to connect motor end plates to a group of muscle fibres, it transmits nerve impulses rapidly to a group of muscle fibres to control them
• Axon potential

  A positive electrical charge inside the nerve and muscle cells that conducts the nerve impulse down the neurone into the muscle fibre
• Neurotransmitter


  A chemical messenger that is produced/secreted by a neuron, it transmits the nerve impulse across the synaptic cleft to the muscle cleft
• All or none law

  When a motor unit receives a stimulus and creates an action potential, if it reaches a certain threshold all fibres contract but if the action potential is below the threshold no muscle fibres contract
• Nervous stimulation of a motor unit

  1. Nerve impulse initiated in the motor neuron

  2. Impulse conducted by the axon of the motor neuron by a nerve action potential

  3. Neurotransmitter secreted into the synaptic cleft to conduct the impulse across the gap

  4. All or none law takes place