What does the brain look like?

What does the brain look like? [All Ages]

Opening Questions

Where is the human brain?

How much does the brain weigh?

Why does the brain have two halves?

Why does the brain look folded?


Show the audience the picture of the human brain and ask them to describe its main features. Pass around something that is 1.5kg heavy and tell them that this is the weight of the average adult human brain.

The Human Brain

Discussion Points

Q1: Why is the brain heavier than most people expect?

A1: The brain is heavy because it is very densely packed with cells. The brain uses 20% of your energy!

Q2: Why is the brain in two halves?

A2: Nobody really knows why the brain is in two halves but we do know that each half controls the opposite side of the body. So the left half of the brain controls the right side of the body and the right half of the brain controls the left side of the body.


Relationship between the left half of the brain and the right half of the body
The left half of the brain largely controls the right side of the body and vice versa
Q3. Why is the brain all folded in on itself?

A3: The part of our brain that is responsible for all our clever thinking is called the ‘cerebral cortex’. The cortex makes up the outer 3-4mm of the brain and is sometimes called ‘grey matter’ to contrast it from the mass of connecting fibres in the centre of the brain which are called ‘white matter’. Below is a diagram of the thickness of the cortex relative to the rest of the brain.

A section of the human brain showing the thickness of the cerebral cortex (dark grey) relative to the rest of the brain (light grey).

Interesting Facts

  • The word “cortex” comes from Ancient Greek and means ‘bark’. Ask the audience why they think that is. Answer: Because it wraps around the outside of the brain like bark wraps around the trunk of a tree.
  • Up to 2 pints of blood flows through your brain every minute!
  • Your brain is 77% water!