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Across 1. Chemical messengers that relay neural messages across the synapse. Many neurotransmitters are also hormones. 4. Cells that bidn the neurons together. Glial cells also provide an insulating covering (the myelin sheath) of the acon for some neurons, which facilitates the electrical impulse. 8. A branched fiber that extends outward from the main cell body and carries information into the neuron. 13. The electrical charge of the axon in its inactive state, when the neuron is ready to "fire". 14. The realying of information across the synapse by means of chemical neurotransmitters. 16. Cell specialized to recive and transmit information to other cells in the body-also called a nerve cell. Bundles of many neurons are called nerves.

Down 2. Refers to the fact that the action potential in the axon occurs either full-blown or not at all. 3. The microscopic gap that serves as a communications link between neurons. Synapses also occur between neurons and the muscles or glands they serve. 5. Tiny bulblike structures at the end of the axon, which contain neurotransmitters that carry the neuron's message into the synapse. 6. A nerve cell that relays messages between nerve cells, especially in the brain and spinal cord. 7. A small "container" holding neurotransmitter molecules that then connects to the presynaptic membrain, releasing the neorutransmitter into the synapse. 9. Nerve cell that carries messages away from the central nervous system toward the muscles and glands. Also called an efferent neuron. 10. 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. 11. Nerve cell that carries messages from sense receptors toward the central nervous system. Also called an afferent neuron. 12. 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. 14. The part of a cell (such as a neuron) containing the nucleus, which includes the chromosomes. Also called the cell body 15. In a nerve cell, 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.