What is the nervous system?

The nervous system controls movement in the body. This system is a collection of billions of cells, which form nerves. that are designed as a communication network within the human body. The nervous system is a “central command centre” that enables the body to gather information about the internal as well as external environment in addition to appropriately respond to it.

There are three primary functions of the nervous system. These are:

• Sensory functioning: The ability of the nervous system to sense changes in either the internal or external environment.
• Integrative functioning: The ability of the nervous system to analyse as well as interpret sensory information.
• Motor functioning: The neuromuscular system’s ability to have the appropriate response to the sensory information.

It is important to remember that all movement is dictated by the nervous system, so it is important to train the nervous system efficiently to ensure that the correct movement patterns are being developed and executed.

What the nervous system is made up of

The Neuron

The cell which does all the work in the nervous system is known as the neuron. Billions of neurons make up the complicated structure of the nervous system. The merging of many neurons together forms the nerves of the body.

Neurons are made up of three parts:

• Cell body
• Axon
• Dendrites

The cell body, or soma, has a nucleus as well as other organelles such as lysosomes, mitochondria and Golgi complex.

The axon transmits nervous impulses and other neurons or sites, e.g. muscles, organs, spinal cord

The dendrites are responsible for gathering information from other structures and sending this information back to the neurons.

There are three main functional classifications of neurons:

• Sensory neurons: Transmits nerve impulses from the effecter sites to the brain or spinal cord.
• Interneuron: Transmits impulses from neuron to neuron.
• Motor neurons: Transmits nerve impulses from the brain and spinal cord to the effector sites.

An example of the way different neurons work synergistically together is seen when a person touches a very hot object.

Central and peripheral nervous system

The nervous system consists of two separate divisions:

• Central nervous system: The brain and the spinal cord make up the central nervous system. The brain and the spinal cord interpret information.
• The peripheral nervous system: This system consists of 12 cranial nerves and 31 pairs of spinal nerves and sensory receptors. They serve two main functions:
• They are the connection for the nervous system to activate and receive information to things such as the muscles.
• They send information from our muscles back to the brain. This means that they are constantly updating information from the body and the environment to the brain.

Sensory receptors

Sensory receptors are structures that are found throughout the body. They transmit environmental information (sound, heat, taste, light) to the brain via the spinal cord to produce an appropriate response.

Sensory receptors can be divided into four main categories:

• Mechanoreceptors : Touch and pressure
• Nociceptors: Pain
• Chemorceptors: Taste and smell
• Photoreceptors: Light and darkness

We, as fitness professionals, concentrate mainly on mechanoreceptors. They are responsible for sensing distortion in the tissue. They are located in the muscles, tendons, joints and ligaments. They sense stretch, compression, traction or tension in the tissue which is then transmitted to the CNS (central nervous system).

Muscle spindles

Muscle spindles are the major sensory organs of the muscles. They sit parallel to the muscle fibres. The muscle spindle is there to control change of length in the muscle, i.e. when the muscle is stretched, so is the spindle. When the muscle is about to be over-stretched the muscle spindle will send a message to the brain and the spindle will then contract the muscle. The muscle spindles prevent the muscles from being over-stretched and injured.

Golgi tendon organs

Golgi tendon organs (GTO) are located at a point where the muscle and the tendon meet. (musculotendinous junction).They are sensitive to rate of change in the muscles. When activated, the Golgi tendon organ will relax the muscle to prevent the muscle from being placed under excessive stress and getting injured.

Joint receptors

Joint receptors are placed in and around the joint. They respond to pressure, acceleration and deceleration of the joint. The joint receptors job is to warn a joint against extreme and harmful positions to prevent injury.

So, as can be seen from the article above, the nervous system is a multifaceted collection of nerves as well as specialised cells that transmit signals between different parts of the body. Essentially, it is the body’s electrical wiring.