How the Brain’s Neurons Communicate

 Let's look at the overall picture to understand how a message is communicated.

  

 1.     The dendrite RECEIVES the message: A neurotransmitter attaches to a receptor on the dendrite of a neuron. This receptor is activated, which causes the neuron to depolarize (change its charge and become more positive). This causes an action potential to be fired and an electrical current is carried toward the cell body.

 

2.     The axon SENDS the message: The axon carries the electrical current away from the cell body toward the axon terminal. Because there is lots of insulation from the fatty tissue (myelin sheath) around the axon, the electric current can travel very quickly.  

 

3.     The message jumps across the synapse to the next neuron: Once the electric current arrives at the axon terminal, it causes sacs to release chemical neurotransmitters. The neuron then loses its electric charge and becomes stable again. The neurotransmitters jump across the synapse and attach to receptors on the next neuron.

 

4.     The whole process starts again: Activating the receptor causes the next neuron to change its charge (become more positive) and a new action potential (electrical message) is fired.

 

How information is sent from one part of the brain to another:

To make things simpler, we have so far looked at single neurons passing on messages to other single neurons.

However there are over 100 billion neurons in the brain and as you can see in the picture below, one neuron can join up (by the synapse) to multiple other neurons forming a complicated matrix with a huge number of synaptic connections. This means that there are thousands of different pathways connecting different areas of the brain and multiple messages can be sent down different pathways at the same time.

 

 

Let’s look at one example of a neuronal pathway...

How is a word that is heard repeated out loud?

When a word is heard, the sound stimulates neurons in the audio cortex (near our ears). The sound message is then communicated from neurons in the audio cortex area to neurons in Wernicke’s area which is concerned with recognizing and comprehending language inputs. 

  • The sound message is then communicated to neurons in Broca’s area, where a plan for speech articulation is added (remember that the bundle of neurons that transmit the message between these two areas has been given a special name - arcuate fasciculus). 
  •  The new message is then communicated to neurons in the motor cortex area (near the mouth). Neurons in this area send the message to muscles in the mouth and throat and the original sound message is repeated out loud.