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| Neuron | A cell specialized for the transmission of impulses; the functional unit of the nervous system |
| Nerve | A bundle of axons that are bound together by connective tissue |
| Dendrite | A short, branched part of a neuron specialized for recieving nerve impulses and transmitting them to the cell body |
| Axon | A long, thin fiber that carries nerve impulses away from the cell body of a neuron |
| Synapse | The region where nerve impulses pass from one neuron to another |
| Neurotransmitter | A substance released by the synaptic knob into the synaptic cleft that initiates impulses in adjacent neurons |
| Receptor | A specialized structure in a nervous system that is sensitive to a certain type of stimulus |
| Impulse | A region of Electrical and chemical charge that passes along the nerve cell membrane |
| Stimulus | Any factor that causes a receptor to trigger impulses in a nerve pathway |
| Brain | A group of specialized nerve cells that control and coordinate the activities of a nervous system |
| Cell Body (Cyton) | The part of a nerve cell that contains the nucleus and is the site of the metabolic activities in the cell |
| Sensory Neuron | A neuron that carries impulses from a receptor toward the spinal cord and the brain |
| Sensory Nerve | A nerve containing the axons of sensory neurons only |
| Motor Neuron | A neuron that carries impulses from the spinal cord and brain toward an effector |
| Interneuron | A neuron that relays impulses from one neuron to another |
| Nerve Net | In the hydra, an interconnected network of nerve cells through which impulses can travel in any direction |
| Central Nervous System | The division of the nervous system that includes the brain and the spinal cord (or in animals, the nerve cord) |
| Peripheral Nervous System | The division of the nervous system that includes all the neurons and nerve fibers outside the brain and spinal cord |
| Cerebrum | The largest part of the human brain |
| Cerebellum | A part of the brain located below the rear part of the cerebrum; coordinates voluntary movements |
| Reflex | An involuntary, automatic response to a given stimulus not involving the brain |
| Autonomic Nervous System | A division of the peripheral nervous system consisting of voluntary motor fibers from the brain and spinal cord that serve the internal organs of the body |
| Ganglion | A group of a cell bodies and associative neurons that switch, relay, and coordinate nerve impulses |
| Medulla | In the brain, the part beneath the cerebellum and continuous with the spinal cord; controls inboluntary actions |
| Spinal Cord | The large nerve connected to the brain at its anterior end and passing through the spinal column; a part of the central nervous system |
| Somatic Nervous System | The division of the peripheral nervous system that contains sensory and motor neurons that connect the central nervous system to skeletal muscles, skin, and sense organs |
| Reflex Arc | The pathway over which the nerve impulses travel in a reflex |
