chapter 3
The Nervous System
The nervous system is the body’s main communication system.
Information is picked up from the Peripheral Nervous System (PNS) and sends this to the Central Nervous System (CNS) to be processed and once processed the CNS tells the PNS what to do! Breathe a bit deeper, flex a muscles etc, etc.
The central nervous system,
The CNS is the main data centre of the body and includes the brain and spinal cord.
Brain
The brain consists of the cerebrum, the cerebellum, and the brain stem.
The cerebrum is the top portion of the brain where the “higher level thought” happens.
The cerebellum is located below the cerebrum and its responsible for balance and maintaining co- ordination throughout the body.
The Brain Stem acts as a relay centre connecting the cerebrum and cerebellum to the spinal cord.
The Spinal Cord
The spinal cord connects the brain stem to all the major nerves of the body. Impulses are sent from the receptors through the spinal cord to the brain where they are processed, and sent back to the spinal cord to muscles and glands …. The result is a reaction!
The Peripheral Nervous system.
PNS includes a large system of nerves that are linked to the brain and spinal cord and communicates information to the CNS.
The PNS can be divided into 2 nervous systems.
The Autonomic Nervous System
This system regulates involuntary actions like internal organ function, and is made up of 2 components which work against each other. The sympathetic nervous system is responsible for your ‘fight or flight’ (reaction to danger) and the parasympathetic nervous system is responsible for ‘rest and digest’ reactions which calms us down.
Somatic Nervous System
This system controls our sudden reflexes and voluntary movement.
What is responsible for transmitting electric messages?
Neurons are responsible for transmitting messages and depending on their roles, the neurons found in the human nervous system can be divided into three classes: sensory neurons, motor neurons, and interneurons.
Sensory neurons get information about what’s going on inside and outside of the body and brings that information into the CNS so it can be processed. For instance, if you picked up a hot coal, sensory neurons with endings in your fingertips would convey the information to your CNS that the coal was hot!
Motor neurons get information from other neurons and convey commands to your muscles, organs, and glands. For instance, if you picked that hot coal, the muscles in your fingers would cause your hand to let go.
Interneurons, which are found only in the CNS, connect one neuron to another. They receive information from other neurons (either sensory neurons or interneurons) and transmit information to other neurons (either motor neurons or interneurons).
For instance, if you picked up the hot coal, the signal from the sensory neurons in your fingertips would travel to interneurons in your spinal cord. Some of these interneurons would signal to the motor neurons controlling your finger muscles causing you to let go, while others would transmit the signal up the spinal cord to neurons in the brain, where it would be perceived as pain.
We have more Interneurons in our system that are involved in processing information, both in simple reflex circuits (like those triggered by hot coals) and in more complex circuits in the brain.
It would be combinations of interneurons in your brain that would allow you to draw the conclusion that things that looked like hot coals weren’t good to pick up, and, hopefully, retain that information for any future hot coal occurrence.
The actual group of muscle fibres in a muscle innervated by a single motor neuron is called a motor unit.
A motor unit controls the skeletal muscles and is the driving force behind every movement you make. This includes voluntary movements like walking or lifting weights, as well as involuntary ones like breathing. As you lift weights, your body adapts to the motor unit it needs.
When discussing nerve responses, you may come across the ‘all or none law’
The all-or-none law is a principle that states that the strength of a response of a nerve cell or muscle fibre is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fibre will fire.
According to the all-or-none law, there will either be a full response or no response at all for an individual neuron or muscle fibre.
This is a great comparison:
Credit: verywell mind
‘This process is like the action of pressing the trigger of a gun. A very slight pressure on the trigger will not be sufficient and the gun will not fire. When adequate pressure is applied to the trigger, however, it will fire.
The speed and force of the bullet are not affected by how hard you pull the trigger. The gun either fires or it does not. In this analogy, the stimulus represents the force applied to the trigger while the firing of the gun represents the action potential.’
Why we need to know about the nervous system/ neuromuscular system.
The neuromuscular system evolves at an early age as we challenge our co-ordination and balance.
Think of how quickly a baby’s reflexes improve from 3 -18 months and a child taking part in activities that challenge their motor skills will have far better motor fitness as opposed to a child leading a sedentary lifestyle.
Loss of cells from the motor system occurs during the normal aging process, leading to reduction of motor neurons plus muscle fibres. This is often combined with the detrimental effects of a sedentary lifestyle in older adults, leading to a significant reduction in reserve capacity of the neuromuscular system. Yet again, this is more reason for you to get out there and get people moving; not just challenging their fitness but their motor fitness, balance co – ordination, so that you are giving your class the skills and physical literacy to understand how their bodies move and to be able to execute those movements in a variety of settings.
…MOVE IT OR LOSE IT!