1. NEURONS!

2. Functions of the nervous system
The functions of the nervous system are
Control functions in the body
Respond to internal and external stimuli
To accomplish these functions, the cells of the nervous system must be able to send messages!

3. Parts of a neuron Dendrites Cell body Axon Axonal terminal Myelin
Carry messages from the environment to the cell body
Cell body
Axon
Carries the impulse away from the cell body
Axonal terminal
Message is sent to the next neuron
Myelin
Fatty covering around axon that makes impulse travel faster

4. The cells of the nervous system
The cells in the nervous system that send the messages are neurons
Neurons send ELECTRICAL impulses!
Your brain, spinal cord, and nerves are made of hundreds of billions of neurons!

6. Types of neurons There are three main types of neurons Sensory neurons
They bring messages from sensory organs to the brain and spinal cord
Motor neurons
They carry messages from the brain to muscles and glands
Interneurons
They connect sensory neurons to the motor neurons
Found in brain and spinal cord
Types of neurons

7. Nerve impulse (Action Potential)
A neuron is stimulated by the environment OR by another neuron
The electrical impulse starts at the dendrites
It travels through the cell body
It travels down the axon away from the cell body
The impulse reaches the axonal terminals

8. Nerve impulse The message is at the axonal terminal
The message needs to be passed to the next neuron
The two neurons DO NOT TOUCH EACH OTHER
There is a gap called a synapse

9. Nerve impulse
When the impulse reaches the end of the first neuron, chemicals called neurotransmitters (NT) are released!
The NT move across the synapse
The second neuron catches the NT
The second neuron is stimulated when it catches the NT
The electrical impulse then starts in the second neuron

10. Nerve impulses
The sending of messages along neurons is happening ALL OF THE TIME in your brain, spinal cord, and nerves!
It is VERY FAST!

11. Neurotransmitters