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.
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 (Nissl bodies)
Membranous sacs within cytoplasm of nerve cells that have ribosomes attached to their surfaces.
Nerve impulses arriving at the same neuron.
Nerve fiber that transmits impulses toward a neuron cell body.
A spreading apart.
A muscle or gland that responds to stimulation.
Subthreshold stimulation of a neuron makes it more responsive to further stimulation.
A mass of neuron cell bodies, usually outside the central nervous system.
A membrane that covers the brain and spinal cord.
Fatty material that forms a sheathlike coveing around some nerve fibers.
Chemical that an axon end secretes to stimulate a muscle fiber to contract or a neuron to fire an impulse.
Sheath formed from Schwann cells on the outside of some nerve fibers.
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.
A network of interlaced nerves or blood vessels.
A rapid, automatic response to a stimulus.
A specialized structure associated with the peripheral end of a sensory neuron specific to dedecting 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.
The junction between the axon of one neuron and the dendrite or cell body of another neuron.