The nervous system is the body’s inner communication system. It’s made up of the body’s many nerve cells. The nerve cells take in information through the body’s senses: touch, taste, smell, sight, and sound. The brain interprets these sensory cues to understand what’s going on outside and inside the body. This allows a person to use their body to interact with their surrounding environment and control their body functions.

The nervous system is very complex. We rely on it every day to help us stay healthy and safe. Why should we appreciate our nervous system? Read these 10 fun facts and you’ll know why:

1. The body has billions of nerve cells

Every person’s body contains billions of nerve cells (neurons). There are about 100 billion in the brain and 13.5 million in the spinal cord. The body’s neurons take up and send out electric and chemical signals (electrochemical energy) to other neurons.

2. Neurons are made of three parts

Neurons receive signals in a short antennae-like part called the dendrite, and send signals to other neurons with a long cable-like part called the axon. An axon can be up to a meter long.

In some neurons, axons are covered with a thin layer of fat called myelin, which acts as an insulator. It helps transmit nerve signals, or impulses, down a long axon. The main part of a neuron is called the cell body. It contains all of the important parts of the cell that allow it to function properly.

3. Neurons may look different from one another

Neurons come in a variety of shapes and sizes depending on where they’re located in the body and what they’re programmed to do. Sensory neurons have dendrites on both ends and are connected by a long axon that has a cell body in the middle. Motor neurons have a cell body on one end and dendrites on the other end, with a long axon in the middle.

4. Neurons are programmed to do different things

There are four types of neurons:

  • Sensory: Sensory neurons deliver electrical signals from the outer parts of the body — the glands, muscles, and skin — into the CNS.
  • Motor: Motor neurons carry signals from the CNS to the outside parts of the body.
  • Receptors: Receptor neurons sense the environment (light, sound, touch, and chemicals) around you and convert it into electrochemical energy that is sent by sensory neurons.
  • Interneurons: Interneurons sends messages from one neuron to another.

5. There are two parts of the nervous system

The human nervous system is divided into two parts. They are distinguished by their location in the body and include the central nervous system (CNS) and the peripheral nervous system (PNS).

The CNS is located in the skull and vertebral canal of the spine. It includes the nerves in the brain and spinal cord. All remaining nerves in other parts of the body are part of the PNS.

6. There are two types of nervous systems

Everyone’s body has a CNS and a PNS. But it also has voluntary and involuntary nervous systems. The body’s voluntary (somatic) nervous system controls things a person is aware of and can control consciously, such as moving their head, arms, legs, or other body parts.

The body’s involuntary (vegetative or automatic) nervous system controls processes in the body that a person doesn’t consciously control. It’s always active and regulates a person’s heart rate, breathing, metabolism, among other critical body processes.

7. The involuntary system is broken down into three parts

The CNS and PNS both include voluntary and involuntary parts. These parts are linked in the CNS, but not in the PNS, where they usually occur in different parts of the body. The involuntary part of the PNS includes the sympathetic, parasympathetic, and enteric nervous systems.

8. The body has a nervous system for preparing the body for action

The sympathetic nervous system tells the body to get ready for physical and mental activity. It causes the heart to beat harder and faster and opens the airways for easy breathing. It also temporarily stops digestion so the body can focus on fast action.

9. There is a nervous system for controlling the body at rest

The parasympathetic nervous system controls bodily functions when a person is at rest. Some of its activities include stimulating digestion, activating metabolism, and helping the body relax.

10. There is a nervous system for controlling the bowel

The body has its own nervous system that just controls the bowel. The enteric nervous system automatically regulates bowel movements as a part of digestion.

11. Your nervous system can be hacked

Scientists are now developing ways to “hack” into the immune system, gaining the ability to control brain cells with the flash of a light. The cells can be programmed to react to light through genetic altering.

Hacking can help scientists learn about the functions of different groups of neurons. They can activate several brain cells at the same time and observe their effects on the body.