1												2			3
																								4
										5
					6
	7														8
	9
														10								11
			12								13															14
								15																					16
17
		18
							19
20
21																							22
						23									24
																			25
				26
	27

Across 1. A sensory nerve ending that responds to a stimulus in the internal or external environment of an organism 5. A muscle, gland, or organ capable of responding to a stimulus, especially a nerve impulse 7. Star-shaped glia that hold neurons in place, get nutrients to them, and digest parts of dead neurons. 8. A glial cell that wraps around the nerve fiber in the peripheral nervous system, and forms the myelin sheaths of peripheral axons 9. The supportive tissue of the nervous system, including the network of branched cells in the central nervous system and the supporting cells of the peripheral nervous system 15. The membrane potential to which a membrane must be depolarized to initiate an action potential 18. A gap occurring at regular intervals between segments of myelin sheath along a nerve axon. 19. A mass of nerve cell bodies 20. Conveys sensory impulses from the blood vessels, the heart and all of the organs in the chest, abdomen and pelvis through nerves to other parts of the brain 21. The part of the peripheral nervous system associated with the voluntary control of body movements 23. A structure that permits a neuron to pass an electrical or chemical signal to another cell 24. The cells which line the ventricles of the brain 25. Special immune cells found only in the brain that can detect damaged or unhealthy neurons 26. The insulating envelope of myelin that surrounds the core of a nerve fiber or axon and facilitates the transmission of nerve impulses. 27. A short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory

Down 2. The portion of the nervous system that is outside the brain and spinal cord. 3. The imbalance of electrical charge that exists between the interior of electrically excitable nerve cells and their surroundings 4. Any of the cordlike bundles of fibers made up of neurons through which sensory stimuli and motor impulses pass between the brain or other parts of the central nervous system. 6. Any of the fibers in a mixed nerve that transmit motor impulses 10. A long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body 11. Short, branching fibers extending from the cell body 12. The basic building blocks of the nervous system 13. The part of the nervous system that consists of the brain and spinal cord. 14. Responsible for the formation of myelin sheaths surrounding axons 16. A nerve fiber that carries impulses toward the central nervous system 17. Endogenous chemicals that transmit signals from a neuron to a target cell across a synapse 22. The part of a neuron containing the nucleus but not incorporating the axon and dendrites