Have you ever wondered how we can feel a mosquito bite, or how we can move our arms or talk? Behind all of this is an amazing network of messengers in our bodies. Today we are going to talk about those "nerves" or in Sinhala, nerves. These are like current-carrying wires.
What exactly are "nerves"?
Simply put, nerves are like a system of electrical cables inside our bodies. These cables are what send electrical impulses from your brain to the rest of your body, and back to your brain. Think about it, nerves help you feel something (e.g., someone touches your hand), move your muscles (e.g., raise your arm), and so on. They also help control autonomic functions that we don't realize we have.
These 'nerves' are made up of special cells called 'neurons' . These 'neurons' are found throughout our bodies, especially in the brain and spinal cord. Doctors usually use the word 'nerves' when talking about the nervous system outside your brain and spinal cord. We call this the 'peripheral nervous system' . Your brain and spinal cord together make up the 'central nervous system' . So when these two come together, our complete nervous system is formed.
Are there types of nerves? What are they?
Yes, there are mainly two types of 'nerves'. Let's see what they are.
What happens to sensory nerves?
These nerves are like the spies in your body. They collect information from different parts of your body (like your skin, eyes, ears, nose, tongue) – that is, touch, taste, smell, sight, hearing – and take it to your brain. Imagine, a mosquito bites your hand, you feel it because of these sensory nerves . That message travels quickly to your brain.
What happens to motor nerves?
These nerves are like soldiers who follow orders from your brain. They take messages from your brain (e.g., 'raise your arm', 'shake your leg') and send them to your muscles and glands. That's when you can move and do different things. For example, when you want to smile, the message from your brain goes through these motor nerves to the muscles in your face, which is what causes that smile.
There are two other main groups of nerves...
Along with the sensory and motor functions mentioned above, nerves can be divided into two other main categories based on how they branch out from our brain and spinal cord.
What are Cranial Nerves?
These are the nerves that start directly from your brain and extend outward. There are 12 pairs of these nerves, to be precise. They mainly extend to your face, head, and neck. These 'cranial nerves' have the ability to perform sensory functions (e.g., smell, sight, taste), motor functions (e.g., eye movement, facial expressions), or both. For example, it is the 'cranial nerves' that help you raise your eyebrows when you are surprised, and it is the 'cranial nerves' that help you smell.
What are Spinal Nerves?
These nerves start in your spinal cord . There are 31 pairs of nerves that branch out from the spinal cord down your spine. These spinal nerves can perform sensory functions, motor functions, or both. For example, when you feel numbness or pain in your limbs, these nerves carry the message to the spinal cord. Also, some of the reflexes that you do without realizing it, such as quickly withdrawing your hand when you touch a hot object, are controlled by these spinal nerves.
What benefits do these nerves have for our bodies?
Now you might be thinking, 'Okay, there are these types of nerves, but what do they do for us?' In fact, without these messengers called 'nerves', we wouldn't be able to do anything. Just look at how many things they control:
- Voluntary movement: These nerves control all the movements we make consciously, such as raising our arms, moving our legs, walking, and talking.
- Feeling all the senses:
- Touch - the feeling of being touched by someone or the wind.
- Pain - The feeling you get when you are injured or hit somewhere.
- Feeling hot or cold.
- Feeling vibration.
- Hearing.
- Sense of balance - helps you avoid falling while walking.
- Sense of taste.
- Sense of smell.
- Sight.
All of this is conveyed to our brain by 'nerves'.
- Controlling blood pressure.
- Breathing control.
- Controlling digestion.
- Heart rate control.
- Stress response: Preparing the body for an emergency.
How do nerves work with other parts of our nervous system?
Okay, now let's see, these 'nerves' don't work alone. They do all this together with the rest of our nervous system. How does that happen?
I've said before that there are two main parts to our nervous system:
1. Peripheral Nervous System (PNS): This is the network of nerves that runs throughout the body. It is like the roads that run throughout the country. These roads (nerves) collect messages (sensations) from different parts of the body and bring them to the main road, which is the spinal cord.
2. 'Central Nervous System' (Central Nervous System - CNS): This is our control center. That is, the brain and the spinal cord . It is this 'central nervous system' that receives all the messages coming from the 'peripheral nervous system', understands them, and decides 'what to do next?'. Then those decisions go back to the relevant places through the 'nerves'.
Think about it this way. You get a thorn stuck in your leg. The pain message is sent by the nerves in your leg (part of the PNS) to your spinal cord (part of the CNS). From the spinal cord, the message goes to your brain (the other part of the CNS). The brain understands, "Oh, a thorn stuck in me, it hurts." Then the brain sends a message back through the nerves to your leg muscles, telling them to "take your leg away." And you take your leg away. All of this happens in the blink of an eye!
Sometimes these responses occur as reflexive actions , that is, before we even think about it, at a lower level of consciousness. An example is the previously mentioned act of withdrawing one's hand from something hot. This happens before the message reaches the brain, where the spinal cord makes the decision and executes it. This allows us to quickly escape harm.
What happens inside a nerve when a message is sent?
This exchange of messages doesn't just happen. It's a very complex, yet amazing process. Let's look at what happens when an electrical impulse travels along a nerve:
1. First, this electrical signal travels along a long wire-like part of the nerve called an 'axon' . Think of it like current flowing through a wire.
2. When it reaches the end of the nerve, called the 'axon hillock' , this electrical signal becomes a chemical signal .
3. Then, this chemical signal causes the release of special chemical messengers called neurotransmitters . These are released from one neuron (nerve cell) into a small gap between the next neuron or a muscle. We call this gap a synapse . It's like a bridge.
4. Those released 'neurotransmitter' particles go to and attach to special 'receptors' on the next 'neuron' or muscle. Just like a key fits into a lock.
5. With this connection, that chemical signal becomes an electrical signal again.
6. Then this new electrical signal travels along that second 'neuron'.
7. In this way, this process continues until the message reaches its target – that is, a location such as the brain, a muscle, or a gland.
Imagine how fast all this happens! Millions of such messages are exchanged within our bodies in a fraction of a second.
Where in our body are these nerves located?
In fact, nerves are everywhere in our bodies! Just like blood vessels are everywhere. Most nerves start in our spinal cord. Some start directly in the brain. Then they branch out throughout the body.
Here are some of the main areas of 'nerves':
- In the hands: Nerves run from your shoulder to your fingertips. Examples include the Ulnar nerve , the Median nerve , and the Radial nerve . Sometimes, when you get hit in the elbow, it feels like an electric shock is going through your hand because the Ulnar nerve is compressed.
- Chest and abdomen: This area contains important nerves, such as the phrenic nerve , which helps with breathing, and the vagus nerve, which is involved in the functioning of many of our internal organs.
- Face: Nerves such as the facial nerve, which helps you smile, talk, and close your eyes, the trigeminal nerve , which brings sensations to the face , and the optic nerve , which carries what you see to the brain, are located in the face.
- In the legs: There are many nerves that control sensation and movement in the legs. Of these, you may have heard of the sciatic nerve . This is the longest and largest nerve in the body. When this nerve is compressed, it causes sciatica. There are also other nerves in the legs, such as the femoral nerve and the tibial nerve .
- Pelvis: This area contains nerves related to the function and sensation of the organs, for example , the pudendal nerve .
Simply put, this network of 'nerves' extends from the tips of your fingers to the top of your head.
How is the structure of a nerve formed?
Okay, let's now look at what's inside a 'nerve' and how it's made. A 'nerve' is like a big cable with lots of little wires inside it.
There are several main parts to a nerve:
- Axons: These are the wire-like bundles of fibers in the middle of the nerve. They are the main pathway for carrying messages.
- Dendrites: These are the branching parts of a neuron that receive electrical messages from other neurons.
- Endoneurium: This is the connective tissue layer surrounding the axon.
- Perineurium: The layer of connective tissue that surrounds the small bundles (fascicles) formed by the bundles of several axons.
- Epineurium: This is the outermost layer of connective tissue that covers the entire nerve, much like the plastic sheath on the outside of a cable.
There is another very important thing, which is called the 'Myelin Sheath' . There are a type of cell called 'Oligodendrocytes' around the 'axons' of the 'nerves' inside your brain, and a type of cell called 'Schwann cells' around the 'axons' of the 'nerves' outside the brain and spinal cord (CNS).
Both oligodendrocytes and Schwann cells contain a fatty substance called myelin. This myelin forms a multi-layered sheath around the axon, called the myelin sheath. This is like the insulation around an electric wire. This myelin sheath is what allows electrical messages to travel very quickly along a nerve. Imagine, if this myelin sheath is damaged, just as the insulation on a wire leaks, the nerves cannot send messages as quickly. Sometimes, messages can stop being sent completely.
Are there any diseases that affect the nerves?
Yes, unfortunately, our very important nerves can also be affected by various diseases and disorders. When nerves are damaged, or when the transmission of messages through them is disrupted, various neurological conditions can occur.
Here are some common conditions that affect the nerves:
- Peripheral Neuropathy: This refers to damage to the nerves outside your brain and spinal cord. This can have many causes. This condition is common in people with diabetes . Symptoms include numbness, tingling, pain, and weakness in the limbs.
- Sciatica: I've talked about this a little bit before. This is when there is pressure or compression on the nerve roots in your lower back, or on the sciatic nerve that runs down your legs. This can cause severe pain and numbness that radiates from your back down your legs.
There are many other conditions like this that can affect the nerves, so if you experience unusual numbness, pain, weakness, or changes in sensation, it's important to see a doctor.
What can we do to keep our nerves healthy?
Our nerves are like a precious resource. So it is our responsibility to keep them healthy and well. To do so, there are some simple, but very important habits we can follow:
- Avoid smoking, or if you smoke, quit: Smoking is very harmful not only to the nerves, but to the entire body.
- Eat a nutritious diet: It is very important to eat a diet rich in whole grains, healthy fats, lean protein, fruits, and vegetables. These provide the necessary nutrition for the nerves.
- Limit alcohol consumption: Excessive alcohol consumption can damage the nerves.
- Control medical conditions that can affect the nerves: For example, if you have a condition like Diabetes Mellitus , controlling it well is very important to protect your nerves.
- Reduce stress: Long-term stress is not good for the nerves. Try to reduce stress through things like meditation and exercise.
- Sleep well: Getting at least 7-8 hours of good sleep every night is very important for the entire body, including the nerves.
- Drink enough water: Keeping the body hydrated also helps keep the nerves healthy.
Following these habits will help you keep not only your nerves, but your entire nervous system healthy.
What else can you ask your doctor about nerves?
If you have any questions or concerns about your nerves, or if you have unusual symptoms, you should definitely see a doctor. When you do, you can ask questions like these:
- ' How do I know for sure if I have nerve pain?'
- 'What is the most likely reason for me to get this kind of 'nerve' pain?'
- 'What tests can I have to check the health of my nerves?'
- 'What treatments can I get to improve the health of my nervous system?'
- 'How can I prevent these 'nervous' problems from happening again?'
It is very important to ask questions like these and gain a clear understanding of your situation.
Finally, things to remember (Take-Home Message)
Okay, so we've talked a lot about nerves today. Finally, the most important thing you need to remember is that nerves are a very amazing, complex system that runs throughout our bodies, from head to toe to be exact.
These 'nerves' connect our brain, spinal cord, and every other part of our body. That's why we can feel, move, think, and speak. Not only that, but these 'nerves' also control 'automatic' things that we do unconsciously, like breathing and digesting food.
So, it's up to you to keep your precious nervous system healthy. Following the health habits I mentioned earlier (eating well, exercising, getting enough sleep, and not smoking) will give your entire nervous system a boost. If you have any concerns, don't hesitate to talk to a doctor. Then you can live a healthy, happy life!
` Nerves, brain, spinal cord, nervous system, sensation, movement
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