How does the brain work?
The brain works like a big computer. It processes information that it receives from the senses and body, and sends messages back to the body. But the brain can do much more than a machine can: humans think and experience emotions with their brain, and it is the root of human intelligence. The human brain is roughly the size of two clenched fists and weighs about 1.5 kilograms. From the outside it looks a bit like a large walnut, with folds and crevices. Brain tissue is made up of about 100 billion nerve cells (neurons) and one trillion supporting cells which stabilize the tissue.
How do neurons work?
Each neuron is made up of three main parts: the cell body (also known as the soma), the axon, and the dendrites. Neurons communicate with each other using electrochemical signals. In other words, certain chemicals in the body known as ions have an electrical charge. Ions move in and out of the neuron across the cell membrane and affect the electrical charge of the neuron.
How does memory work?
Neurons (nerve cells in the brain) communicate through synaptic connections (structures that pass a signal from neuron-to-neuron) that "talk" to each other when certain neurotransmitters (chemicals that allow the transmission of these signals) are present.
Think of a neurotransmitter as an email. If you're busy and you receive one or two emails, you might ignore them. But, if you are bombarded with hundreds of emails from the same person, saying basically the same thing, all at the same time, you will likely begin to pay attention and start a conversation with the sender: Why on earth are you sending me all these emails?
Similarly, neurons only open a line of communication with each other when they receive stimulation from several of the same neurotransmitters at once: Oh, my neighbor keeps hitting me with the same signal? I better talk to them! So, how exactly does this relate to memory? It's the strength of these connections between neurons that determines how a memory is formed.