Nervous System – The Basics.
The Nervous System is split into two section, the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS is made up of the BRAIN and the SPINAL CORD while the PNS is made up of all of the OUTSIDE MECHANISMS associated with the Nervous System and is split into a further two sections (Somatic and Autonomic/Voluntary and Involuntary).
There are several roles of the nervous system:
- Initiating movement – either voluntary/consciously or involuntary (reflexes)
- Control and coordination of movements
- Sensory feedback and adaptation – such as being aware of how heavy something and knowing how much force to use to lift it.
NEURONES are made up a cell body (SOMA), DENDRITES and an AXON. The axon is oftensurrounded by capsules of MYELIN separated by the NODES OF RANVIER, which speed up the contraction of the nerve impulse. They play a major role in the nervous system by receiving and processing signals before transmitting appropriate responses via other nerve impulses, all of which transfer from primary, secondary and tertiary neurones through the axon terminal across a SYNAPSE.
Before nerve impulses can be sent, an action potential must initially be triggered via ‘DEPOLARIZATION’ of the neurone. This ‘activation’ will only occur if depolarization is big enough to allow enough chemical mediators (Sodium ions) to travel through the neurone, part of a process known as the ‘ALL OR NOTHING LAW’.
Neurones also make spinal nerves which in turn contribute to making a MOTOR UNIT (made of lower motor neurones and muscle fibres). Nerves are classified into THREE types: AFFERENT/ASCENDING and send signals from the sensory neurones in your peripheries to the brain/CNS; EFFERENT/DESCENDING and send signals from the brain/CNS to the target muscles/glands/peripheries; and MIXED which contain both afferent and efferent axons therefore conduct incoming sensory information and outgoing muscle commands. Motor units vary in size and are recruited/used in size order (smallest to largest). Therefore the smaller motor units in the quadriceps muscles will be recruited before the larger motor units. This is known as ‘THE SIZE PRINCIPLE’.
The whole point of neurone, spinal nerves and motor units is to make up the nervous system of which one of the major roles is to control and perform reflexes, as mentioned earlier. REFLEXES and how they help prevent injury while training will be elaborated on in my next post.