The central nervous system (CNS) is the main control center of your body. It receives information, processes it, and then tells your body how to respond. Basically, it’s in charge of everything you do, from thinking and moving to breathing and digesting.

The CNS has two main parts:

• The Brain – controls thinking, memory, movement, and vital functions like breathing and heartbeat.

• The Spinal Cord – connects the brain to the rest of the body and helps send messages back and forth.

Both the brain and spinal cord are protected by three layers of tissue called meninges, and they are enclosed by bones: the skull for the brain and the vertebral column (spine) for the spinal cord.

How the CNS Works

Your brain controls your thoughts, emotions, and movements. It manages both voluntary actions (like waving your hand) and automatic actions (like breathing and digesting food).

Here’s how the process works:

1. The brain creates an electrical signal (a message).

2. The spinal cord carries that signal to the nerves in your body (part of the peripheral nervous system, or PNS).

3. The nerves then activate your muscles or organs to complete the action.

This communication happens constantly to keep your body functioning properly.

Cranial Nerves

There are 12 pairs of cranial nerves in total. These nerves are part of the peripheral nervous system (PNS) and connect the brain to different parts of the head, neck, and body.

Each cranial nerve has a specific function: some carry sensory information (like sight or smell), some control muscles (motor function), and some do both (mixed nerves).

• Cranial Nerves I and II (Olfactory and Optic) come directly from the cerebrum (forebrain).

• Cranial Nerves III–XII come from different parts of the brainstem.

The 12 Cranial Nerves and Their Main Functions

• Olfactory Nerve (Cranial Nerve I) – This is a sensory nerve responsible for your sense of smell.
  
  

• Optic Nerve (Cranial Nerve II) – This sensory nerve allows you to see by carrying visual information from your eyes to your brain.

Main parts of the Central Nervous System

The CNS has two main parts:

The Brain - the command center that processes information and controls the body.

1. • Frontal Lobe controls voluntary movement, attention, short-term memory, motivation, planning, and speech production. It’s also involved in decision-making and personality.

   • Parietal Lobe processes touch, pressure, and body position (proprioception). It also helps with language understanding and spatial awareness - knowing where things are around you.

   • Temporal Lobe helps with hearing, understanding speech, and forming memories. It also plays a role in recognizing sounds and objects.

   • Occipital Lobe is the center for vision. It receives and processes visual information from your eyes, helping you recognize shapes, colors, and motion.

   • Limbic Lobe controls emotions, learning, and memory. It also helps regulate automatic body functions like heart rate and emotional responses.

   • Insular Lobe is involved in taste, pain, emotion, and internal body sensations (like hunger or heartbeat). It also helps with balance and body awareness.

Gray Matter and White Matter

The CNS is made up of billions of nerve cells called neurons. Each neuron has:

• A cell body (the main part)

• Dendrites (short branches that receive messages)

• Axons (long branches that send messages)
  
  

Axons are often covered with myelin, a white, fatty substance that helps signals travel faster.

Because of this, the CNS has:

• Gray matter – made up of neuron cell bodies

• White matter – made up of myelinated axons (the “wiring” that connects different parts of gray matter)
  
  

In the brain, gray matter is mostly on the outside (the cortex) and white matter is deeper inside.
In the spinal cord, it’s the opposite: gray matter is inside, shaped like a butterfly, and white matter is on the outside.

Ready to test what you've learned?

Play through the games below to test your understanding and sharpen your skills.