As I told you all before the nervous has been my favorite out of all the systems in the human body and one of the reason for that is the nerve cells which make up the system. Sure the brain and the spinal cord are the main components of the nervous system, but the nerve cells are the reason behind the connection of different muscles and organs.
There are a few different kind of nerve cells, also known as neurons; which is obvious considering each type is responsible for a particular type of communication and they are known as sensory neurons, motor neurons and interneurons. There are more but I will discuss the others in a different post.
Three Faces of Neurons
The sensory neurons are also known as afferent neurons are responsible for transmitting sensory information which is taken from different parts of the body and delivered to the brain and spinal cord. This includes information such as tactile or visual stimuli and if it weren’t for these sensory delivery boys, you would not be understanding what you see and touch. Instead of internal changes, sensory neurons take in information from the outside.
Motor neurons, or efferent neurons as the name suggests are responsible for your movement and motor functions. Unlike sensory neurons, motor neurons take information from the brain and spinal cord and transfer it to the muscles in different parts of the body. The area between a motor neuron and the muscle fiber is known as neuromuscular junctions and these are the most common types of neurons in the human body.
The third type of neurons are known as interneurons which are present amongst other neurons and if judging by the population, then interneurons have the highest number as compared to other two. They are present in the brain and spinal cord and are mainly involved in reflexive behavior and what is known as the reflex arc.
Reflexive behavior is a survival tactic taken by your body in order to prevent injury and interneurons come in pretty handy when you want to save yourself from severe injuries.
You might have experienced this, when you are working in the kitchen. You are baking brownies or pizza—whatever suits your mood—and when it is time to take the brownie tray out of the oven, you forget to put on your oven mitt and try to take out the tray with your bare hand.
As soon as you experience the searing pain in your hand, you immediately wrench your hand away from the hot surface. Now you might think your brain gave that command, but in reality it was the interneuron sending a message to the motor neuron in your hands that you are in pain and that is why you immediately remove your hand. If the neurons decide to send the information to the brain first, then it might be too late and you would end up seriously injured. And that folks, is what is known as reflex arc.
Two systems, One family
Now that we have gotten the neurons out of the way, let’s get down to the main chunk of the nervous system. Yes, the neurons are little workers, working hard to relay information to and from the brain and spinal cord, but what goes on up in the main powerhouses—the brain and the spinal cord—which make up the nervous system.
The nervous system itself is divided into two parts, the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Though the CNS consists of the brain and spinal cord, PNS consists of nerve tissues and fibers which branch out and connect to the other parts of the body. And the peripheral nervous system is further divided into somatic and autonomic nervous system which we will talk about in a little while.
Considering we are all aware of what the central nervous system is responsible for as it consists of the brain and spinal cord, the peripheral nervous system is what drives people into a pickle because it extends to the rest of the muscles and organs of the human body. And if it wasn’t for PNS we would not be comprehending our reality and environment as we are able to do so.
I didn’t do it on purpose, did I?
The peripheral nervous system as stated above branches out into somatic and autonomic nervous system. And both of these play a critical role in our actions regarding living and surviving in this world.
Now the somatic nervous system is responsible for all your voluntary actions, to say so in simple words. You stand up, sit down, run around, all of these voluntary actions are handled by the somatic nervous system. You are able to control your movements because of the somatic nervous system.
The autonomic nervous system does the opposite, in the sense that it is responsible for all the involuntary actions needed to ensure your survival, and this includes breathing, heart rate, pupil dilation, perspiration and salivation amongst others.
Fight or Flight?
This autonomic nervous system further spreads out into sympathetic and parasympathetic nervous system and the interesting thing about these two is that, these two work in opposition to each other, meaning they do the opposite of one another. Where the sympathetic nervous system results in faster heartrate and inhibition of digestion, the parasympathetic nervous system lowers heartrate and accelerates your digestion.
So if you are walking in a jungle and a lion decides to chase after you, the sympathetic and parasympathetic nervous systems will be activated because you are in a stressful situation and when your survival instincts kick in, that is when the sympathetic nervous system is activated and your heart picks up speed while parasympathetic increases your digestion, so that you will have enough energy to either fight the lion or run from it. All the physiological changes that take place are the result of these two systems activating; such as the dilation of your pupils so that more light can enter your eyes and the release of the hormone adrenaline in order to give you an energy boost so that you can make a quick decision and save your life.
Food for Thought
So after going through all the information give above, I just have one thing for you guys to ponder over:
- At times when a threatening situation arises, instead of fighting or fleeing, one tends to freeze. What do you think is the reason behind that?