The nervous system making you feel nervous? For those of us who only vaguely remember the body systems from back in high school, we’re going through it all for you!
The nervous system is a complex collection of nerves and specialised cells—known as neurons—that help different parts of the body communicate, and allow the brain to control bodily functions. The central nervous system consists of the brain and the spinal cord. The rest of the nerves together belong to the peripheral nervous system.
What is the Nervous System?
The nervous system is made up of two parts – the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS is the command centre of the body; made up of the brain and the spinal cord. The brain is central in controlling bodily functions including sensation, thought, awareness, movement and memory. Some reflex movements occur via spinal cord pathways without the involvement of brain structures – unfortunately, this refers to the reflex to remove your hand from a burning pan, not a reflex of disgust at Donald Trump. The brain is connected to the spinal cord, which runs through the spinal canal and carries communication signals back and forth between the brain and the peripheral nerves.
The PNS is like electrical wiring that carries impulses around the body. It is made from neurons, ganglia (neuron clusters) and nerves that connect the central nervous system to the appendages, including hands, feet, etc. There are two main types of nerves:
- Sensory nerves carry sensory information to the brain to tell it about what is going on in the outside world. These nerves deal with the 5 senses; sight, hearing, taste, touch and smell; and are what make cake so enjoyable.
- Motor nerves allow the brain to control our muscles. The brain sends messages over the motor nerves to tell our muscles to expand or contract in order to control movement.
(It isn’t 100% clear which one of these would be your last nerve that you accuse someone of getting on, but at least now you have a diagram to show exactly how annoyed you are).
But How does the Nervous System Work?
The CNS and the PNS are the main structural nervous systems within the body, however in order for the entire nervous system to function, the two main subdivisions: the autonomic and somatic, have to get involved.
- Autonomic nervous system is involuntary: this set of nerves regulate some body processes. They connect the central nervous system to the lungs, heart, stomach, intestines and sex organs. The autonomic nervous system ensures that our hearts beat and that our digestive system releases the necessary enzymes.
- Somatic nervous system are the nerves that we actively control, connecting with muscles and sensory receptors in the skin. These are voluntary and as such require conscious effort, for example we jump using our legs, and clench our fists to punch Nazis.
What Makes Neurons Special?
I said that neurons are specialised cells, they are a little different to the old cell diagram you’ve seen labelled in science classes on TV. Neurons have three important parts, the cell body, the axon, and the dendrites, and they look like you’ve splatted something on the floor (see below).
- The main cell body is mostly similar to cells elsewhere, is generally round-ish and has a nucleus and everything else you can remember (and the stuff you can’t).
- Dendrites branch off of the main cell body, and they receive messages from other cells; one neuron can have hundreds of dendrites or just one, depending on how many different messages they need to process.
- The axon is where the neuron sends the message on to the next cell. Depending on what message or what collection of messages comes in, the neuron either will or won’t trigger messenger chemicals known as neurotransmitters to be released at the synapse—a gap between neurons—which then passes information to the dendrite of the next neuron.
The signals that come up and down the dendrites and the axons are electrical, so neurons are covered in insulation to prevent short circuiting. (Editors Note: When I was in high school, we were told it was enough electricity to power fairy lights. I always wanted to know if that would be testable.)
What Illnesses and Conditions are Common to the Nervous System?
The most common issue with diseases of the nervous system is pain. One way or another, chronic pain is usually prevalent. Nerve disorders are particularly difficult as they reduce a person’s ability to function and/or control their body.
- Parkinson’s disease is a progressive nerve disease that affects movement.
- Motor neuron disease, also known as Amyotrophic lateral sclerosis (ALS), or Lou Gehrig’s disease, weakens the muscles and progressively blocks physical function. This has gained a lot of publicity in recent years thanks to the Ice Bucket Challenge.
- Epilepsy is when abnormal electrical discharges from brain cells cause seizures.
- Multiple sclerosis (MS) is when the protective insulation of the nerves is attacked by the immune system.
- Huntington’s disease is an inherited condition that cause the nerve cells in the brain to degenerate.
- Dementia covers a wide range of disorders including Alzheimer’s disease that impact mental functions, particularly memory.
You may have heard various mental illnesses be referred to as “chemical imbalances”, this usually refers to problems with the neurotransmitters at the synapse – and having too much or too little of them, which results in messages getting mixed up.
If you’re concerned about any of the above, please see your GP or visit the NHS website through any of the links above for general overviews of the conditions.
Editors Note: Here at The Nopebook we want to help you to understand your body, what is supposed to be going on, and what could be going wrong – but we are not health professionals or doctors. The above is for information only, to give you a better understanding, and does not replace a trip to the doctors.