Download Nervous system - Southend PT Academy

The nervous system
page 30-34
Southend Personal Trainer Academy
Role of the nervous system (page 30)
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Sensation – sensory nerves around the body monitor the internal and external
environment
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Analysis – the brain then analyses the signals and dictates an appropriate
response
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Response – the appropriate action is then taken this could be movement via
motor nerves or it could be
Structure of the nervous system (page
31)
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Central nervous system
The central nervous system is like the command centre for the entire nervous
system. It is made up of the brain and the spinal cord.
All nerve impulses originate from the CNS
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Peripheral nervous system
Consists of all the branches of nerves that lie outside of the spinal cord. There
are two subdivisions of the PNS. They are the somatic system and autonomic
system
Somatic & Autonomic systems (page 32)
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Somatic system
The system that controls voluntary movement of the skeletal muscles for
example a bicep curl
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Autonomic
The systems that controls involuntary functions for example digestion
Principles of muscle contraction (page
32)
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The nervous system controls every action of the muscular system
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Information gathered by the eyes will help the central nervous system judge
the weight and the required position to lift an object
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Motor units within the muscles then make the muscles contract
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The muscles pull on the bones and create movement of the joints
Nervous system overview (page 30-32)
All or none law (page 33)
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Within the muscles you have motor units
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A motor unit is a motor neuron and all of the muscle fibres it activates
(innervates)
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One motor neuron may innervate up to 1000 muscle fibres depending on its
location and function
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When an impulse is sent to a motor unit all the muscles fibres that are
attached will be activated or none of them will
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This is called the “all or none law”
Number of motor units (page 33)
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The number of motor units in a particular area depend on the location of the
muscle and its function
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Muscles that control posture have fewer motor units supplying more fibres
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Muscles involved in intricate movements have more motor units supplying less
fibres
Neuromuscular connections and exercise
(page 33)
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Exercise can help to enhance neuromuscular connections which help improve
motor fitness
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Long term the nervous system will be able to recruit more motor units, this
increase the strength of muscular contractions and force generation
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This is why after a few months of weight lifting a beginner might have a
sudden increase in “strength” when in reality it is an increase in motor unit
efficiency
Muscle sense organs (page 34)
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Joint receptors – are found in the ligaments and joint capsules, they tell the
brain about positioning of the joint
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Muscle spindles – found in the muscle and tell the brain how stretched the
muscle is and how many motor units to fire
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Golgi tendon organs – located in the tendons, they tell the brain how much
force has been generated in the muscle. If the force is too great they cause
the muscle to relax