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Across 2. motor pathways of the peripheral nervous system that lead to the skin and skeletal muscles 5. chemicals that axons secrete on effectors or other neurons 6. a nerve that consists of motor neuron axons. 8. neuroglial cells that line the ventricles of the brain. 10. a type of neuroglial cell that forms myelin 15. The brain and spinal cord 16. specialized cells of the nervous system that produce myelin, communicate between cells, maintain the ionic environment, and nurture the differentiation of neurons. 20. specializes structures associated with the peripheral ends of sensory neurons specific to detecting a particular sensation and triggering nerve impulses in response which are transmitted to the central nervous system. 22. the sequence of electrical changes that occurs in a portion of a nerve cell membrane that is exposed to a stimulus that exceeds the membrane's threshold. 23. spaces between the schwann cells and nerves will inpulse 24. a neuroglial cell that supports neutrons and phagocytizes. 25. a nerve fiber. it conducts a nerve impulse away from the neuron cell body. 26. part of nervous system that controls the viscera 27. nerve cells

Down 1. Part of the nervous system outside the central nervous system 3. portion of nerve cell that includes a cytoplasmic mass and a nucleus and from which nerve fibers extend 4. a type of neuroglial cell that connects neurons to blood vessels. 7. a nerve composed of sensory nerve fibers 9. a type of neuroglial cell that surrounds an axon of a peropheral neuron forming the neurilemmal sheath and myelin. 11. a bundle of axons in the peripheral nervous system. 12. stimulation level that must be exceeded to elicit a nerve impulse or a muscle contraction. 13. the difference in electrical charge between the inside and the outside of an undisturbed nerve cell membrane. 14. the functional connection between the axon of a neuron and the dendrite or cell body of another neuron or the membrane of another cell type. 17. masses of neuron cell bodies, usually outside the central nervous system 18. fatty layers formed from certain neuroglial that surround anon. providing insulation. 19. process of a neuron that receives input from other neurons. 21. muscles or glands that effect changes in the body