Muscle Fibres Learning Outcomes  All are able to apply knowledge of the fibres to sporting events  Most are able to explain the role of the motor unit in contraction.  Some are able to apply knowledge to a range of sporting activities.

 Write up a neat copy of your extended question to be marked  Prepare for Mock exam – Tues 7 th October  Bring in file with all Muscle Notes Homework

 Question chain activity to recap muscle fibres.  Complete exam question Starter Activity

 The motor unit is the basic functional unit of skeletal muscle.  The motor unit is the motor nerve (neurone) and the group of muscle fibres that it controls.

 Stimulation of one motor neuron causes all the muscle fibres in that motor unit to contract simultaneously.  Each muscle is made up of a number of units. The number recruited varies depending on strength required.  Number of fibres within a motor unit is dependent on control required.  Small muscle for fine motor skill may only require one fibre per motor unit e.g. eye to focus  Large muscle for gross skill may need 500 or more fibres e.g. kicking a football Motor unit

 Motor units are usually made up of the same muscle fibre.  So we see both fast and slow twitch motor units in a muscle. Motor unit

 The innervation (stimulation) of a muscle occurs when a motor neuron transmits a nerve impulse to the muscle fibre.  The all or none law states that if a motor impulse is of sufficient intensity, the motor unit is stimulated and all the muscle fibres within it will contract to their maximum potential.  Either the neurone will fire a response or it won't. There is no partial response. All or none law

 Give handout – diagrams  The force exerted by a muscle is dependent on:  Recruitment: the more motor units recruited, the more muscle fibres that contract, thus increasing the force produced.  Frequency: decreasing the time between impulses so that the muscle fibres do not have time to relax, resulting in a continuous wave of contractions known as wave summation. Graduation of contraction

 Timing: spatial summation – To create a greater force of contraction the brain recruits more and larger motor units.  Use bigger/larger motor units  More motor units  More and larger units leads to increased strength/more force in muscles  FT units produce more force than ST units. Graduation of contraction

 Resistance training will result in some long term physiological responses to the neuromuscular system:  Recruitment of more motor units (trained to act together)  Muscle hypertrophy (due to increases in size of fibres or hyperplasia – splitting of fibres)  Conversion of type 2b to type 2a (delays fatigue in prolonged training). Effect of training

 Individually explain how the strength of muscle contraction can be varied in relation to a high jumper and a distance runner.  Share this information with a partner between you come up with an agreed answer.  Be prepared to share this information Plenary Activity

The strength of a muscle contraction can be increased  Use bigger/larger motor units  More motor units  More and larger units leads to increased strength/more force in muscles  FT units produce more force than ST units.  All or none law  If all motor units are stimulated at same time then max force can be applied  High jumper – predominantly FT muscle fibres  Marathon runner – predominantly ST muscle fibres Plenary activity

 Complete this question in pairs:  How can a performer vary the strength of muscular contractions to ensure that a skill is completed correctly? (4 marks) Exam Q

A. (Greater the force needed) larger motor units recruited B. More units recruited C. Need fast twitch fibres rather than slow twitch fibres D. Multiple unit summation/spatial summation E. All or none law/All or nothing law/or explanation F. Wave summation/frequency of impulse/innervations G. Motor unit unable to relax/increase the force H. Tetanus/titanic for powerful contraction I. Muscle spindles detect changes in muscle length/speed of contraction J. Send information to brain/CNS K. Compares information to long term memory to ensure correct force applied/past experiences L. Spatial summation – rotating the frequency of the impulse to motor units to delay fatigue

 In pairs use your notes to complete a draft version of the extended question. Extended question