The nervous system is simply the part of an organism that brings together and coordinates its actions by transmitting signals to-and-fro from every single part of its body. It detects environmental changes in the immediate surroundings and affects the body and then work as a unit with other body system to respond to such events.
The nervous system is found mostly in complex multicellular organisms, such as ours, but vary in the level of complexity in which they exist. The only multicellular organisms with no nervous system are organisms like sponges, mesozoans and placozoans, which have a rather simple body. Pretty interesting right? Lets finds about more about it. Here are some interesting facts about the nervous system that you probably don’t know.
12. The CNS and PNS
In humans and other vertebrates, the nervous system is divided into two parts; the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system consists of the brain and the spinal cord. The PNS constitute all the remaining parts of the nervous system in other body parts.
11. Division in the Peripheral Nervous System
The main job of PNS is to connect each and every limb and organ to the brain or CNS. The peripheral system is actually divided into two broad sections; the somatic part and the visceral part. First the somatic part is composed of a web of nerves that connects the spinal cord with every muscles, skin and joints in the body.
On the other hand, the visceral part consists of neurons that connects blood vessels, glands and organs in our body. The visceral nervous system is further divided into two parts, i.e the sympathetic nervous system and the parasympathetic nervous system.
10. Nervous system disorders
Destruction of myelin sheaths of neurons in MS
Have you ever heard of a disease known as Multiple Sclerosis or MS, what is it? Multiple sclerosis is one of the most common autoimmune diseases, in which the protective covers of nerve cells in our spinal cord and brain get severely damaged. The disorder affects the ability of the nervous system to communicate and can trigger mental and psychiatric problems. Meningitis, Arachnoid cysts and Autism are some of the well-known disorders associated with the nervous system.
The human brain is divided into two hemispheres. The right side of the brain controls muscles on the left side of the body, whereas the left hemisphere controls the actions of the muscles of the right side of your body. On a different note, things get more complicated in the case of human vision.
Optic nerves from the right sides of both eyes is connected to the right side of the brain and nerves from the left side of each eye is connected to the left hemisphere of the brain.
8. Glial cells
Glial are supportive non-neuronal cells that help maintain homeostasis (stable equilibrium), create myelin and assist neurons in the signal transmission process in the nervous system. They also play an important part to eradicate pathogens and clean up dead neurons.
Wondering what is myelin? Well, myelin is a greasy substance that creates a coating around axons to provide them with insulation, which allows them to transmit more efficiently. According to researchers, these cells exist in almost the same proportion as the neurons in the human brain with slight variation in different areas of the brain.
7. Mirror neurons
A newborn monkey imitates tongue expression
A mirror neuron is a neuron that activates when an animal observes an action performed by others and repeats it. So basically the mirrors neurons imitates the behavior of the others. Such neurons have been successfully observed in various primate species. Though, a large scientific group has welcomed the discovery of such neurons in humans, others have expressed fair doubts over its existence and role in human body.
6. Different Types of Neurons
Neurons or nerve cells in our body exist in varied shapes and sizes. They can be categorized based on their functions and morphology. One of the pioneers of the field and anatomist Camillo Golgi grouped neurons into two broad groups; neurons with long axons and neurons with smaller neurons.
5. Voluntary and Involuntary Movement of the Muscles
Spinal Cord not only controls voluntary movements such as picking up something or pushing something, but also dictates the involuntary movements or unconscious decisions performed by our body such as diaphragm, bowels, and bladder movements.
4. The Sympathetic Nervous System
Illustration of sympathetic nervous system
The sympathetic nervous system can be divided into two categories- the autonomic nervous system, the other being the parasympathetic nervous system. In layman terms, the sympathetic nervous system prepares the body for any physical and mental exercise. It can cause heart beat faster, open air passages in lungs, decrease movement of large intestine etc.
3. Neurons are programmed to do different things
Do you know neurons are of four types? The receptor neurons, which senses the surrounding environment like touch and light and convert it into electrochemical energy. These electrochemical signals are then delivered to the central nervous system by another type of neurons known as Sensory neurons.
Motor neurons then carry signals from central nervous system back to the muscles and organs in our bodies. Interneurons, also known as the relay neurons enables communication between motor neurons and sensory neurons.
2. Nerve Cells Are Made of Three Parts
Image Courtesy: io9.gizmodo
Each nerve cell can be divided into three parts. These are dendrites, axons and axon terminals, which carry out the important function of communication within our body. Nerve cells or neurons receive signals through many antennae-like parts called dendrites. They then relay those signals to other neurons via axons and axon terminals.
Technically, they have a fourth part known as soma or more commonly the cell body. It carries the important part of the cell.
1. The Number of Neurons Present in Our Brain
Multipolar Neuron Image Courtesy: BruceBlaus
Despite the popular believe that our brain contains nearly 100 billion neurons, almost equal to stars in the Milky way galaxy, we are neither able to accurately estimate the amount of stars present in our galaxy nor the neurons in our brain thus far. However, researchers now and then come up with a new theories and numbers. In a more recent study, scientists estimated that there are about 86 billion of neurons present in our brain.
Some Short Facts
1. Sometimes the spinal cord acts independently of the Brain. In other words, your spinal cord can send signals directly to the muscles, without the consent of your brain.
2. Do you know your spinal cord stopped growing after the age of 5 or 6? Yes, that is correct. In an average human body, the spinal cord goes through intense growth in the first four years and can grow up to about 16 or 20 inches long, but after that it become stagnant irrespective of the total body growth.
3. Perhaps the longest neurons in an average human body are actually a part of the sciatic nerve (largest nerve), running from the toe to the spine.