NEURONS!

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!

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

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!

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

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

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

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

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!

Neurotransmitters