Term | Definition |
action potential | the sequence of electrical changes when a nerve cell membrane is exposed to a stimulus that exceeds its threshold |
autonomic nervous system | portion of nervous system that controls the actions of the viscera |
axon | a nerve fiber that conducts a nerve impulse away from a neuron cell body |
central nervous system (CNS) | portion of nervous system that consists of the brain and spinal cord |
chromatophilic substance | membranous sacs within cytoplasm of nerve cells that have ribosomes attached to their surfaces |
convergence | nerve impulses arriving at the same neuron |
dendrite | nerve fiber that transmits impulses toward a neuron cell body |
divergence | a spreading apart |
effector | a muscle or gland that responds to stimulation |
facilitation | subthreshold stimulation of a neuron makes it more responsive to further stimulation |
ganglion | a mass of neuron cell bodies, usually outside the central nervous system |
meninges | membranes between the bone and soft tissues of the nervous system, protects the brain and spinal cord |
myelin | fatty material that forms a sheath-like covering around some nerve fibers |
neurilemma | sheath formed from Schwann cells on the outside of some nerve fibers |
neurotransmitter | chemical that an axon end secretes to stimulate a muscle fiber to contract or a neuron to fire an impulse |
parasympathetic nervous system | portion of the autonomic nervous system that arises from the brain and sacral region of the spinal cord |
peripheral nervous system (PNS) | the portions of the nervous system outside the central nervous system |
plexus | a network of interlaced nerves or blood vessels |
reflex | a rapid, automatic response to a stimulus |
sensory receptor | a specialized structure associated with the peripheral end of a sensory neuron specific to detecting a particular sensation and triggering a nerve impulse in response, which is transmitted to the central nervous system |
somatic nervous system | motor pathways of peripheral nervous system that lead to the skin and skeletal muscles |
sympathetic nervous system | portion of the autonomic nervous system that arises from the thoracic and lumbar regions of the spinal cord |
synapse | the junction between the axon of one neuron and the dendrite or cell body of another neuron |