2. The Neuron The building block of the nervous system. Neuron – A cell specialized to receive, process, and transmit information to other cells. Bundles of neurons are called nerves.

3. Types of Neurons Sensory (afferent) Neurons – Act like one-way streets that carry traffic from the sense organs toward the brain. Treat the brain to sight, taste, hearing, touch, smell, pain, and balance. Ex. – When you test the water temperature in the shower with your hand, afferent neurons carry the message toward the brain.

4. Types of Neurons Motor (efferent)Neurons – Form the one-way routes that transport messages away from the brain to the muscles, organs, and glands Ex – In our shower example, motor neurons deliver the message from the brain that tells your hand just how much to move the shower control knob.

5. Types of Neurons Interneurons – Relays messages between other neurons, especially in the brain and spinal cord. Brain is basically a network of billions of intricately connected interneurons.

6. How Neurons Work Dendrites – A branched fiber that extends outward from the main cell body and carries information into the neuron. Act like a net that collects messages.

7. How Neurons Work Soma – Part of the neuron containing the nucleus. Receiving information from the dendrites and then makes the decision to either pass the information on or stop it.

8. How Neurons Work Axon – An extended fiber that conducts information from the soma to the terminal buttons. Information travels along the axon in the form of an electric charge called the action potential.

9. The Resting Potential Resting Potential – The electrical charge of the axon in its inactive state, when the neuron is ready to fire. http://www.youtube.com/watch?v=YP_P6bYvEj E http://www.youtube.com/watch?v=YP_P6bYvEj E

10. The Action Potential Action Potential – The nerve impulse caused by a change in the electrical charge across the cell membrane of the axon. When the neuron fires, this charge travels down the axon and causes neurotransmitters to be released by the terminal buttons. Sets off a chain reaction like a set of falling dominos.

11. The Action Potential All-or-None Principle – Refers to the fact that the action potential in the axon occurs either full-blown or not at all.

12. Synaptic Transmission Synapse – The microscopic gap that serves as a communications link between neurons. Synapses also occur between neurons and the muscles or glands they serve.

13. Synaptic Transmission Terminal Buttons – Tiny bulblike structures at the end of the axon Contain neurotransmitters that carry the neuron’s message into the synapse.

14. Synaptic Transmission Synaptic Transmission – Sequence of events in which the electrical message morphs into a chemical message that easily flows across the synaptic gap or cleft between neurons.

15. Neurotransmitters Neurotransmitters – Chemical messengers that relay neural messages across the synapse. Many neurotransmitters are also hormones.

16. Plasticity Plasticity – The nervous system’s ability to adapt or change as the result of experience. Plasticity may also help the nervous system adapt to physical damage. Hugely important in helping us survive.

17. Glial Cells Glial Cells – Cells that bind the neurons together. Also provide an insulating cover (the myelin sheath) of the axon for some neurons, which facilitates the electrical impulse.