Nervous System Vocabulary 2

Axon Terminal
contain hundreds of tiny vesicles, or membranous sacs, that contain chemicals called neurotransmitters
a chemical that is released from a nerve cell which thereby transmits an impulse from a nerve cell to another nerve, muscle, organ, or other tissue. A neurotransmitter is a messenger of neurologic information from one cell to another
Synaptic Cleft
a tiny gap between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter
the place at which a nervous impulse passes from one neuron to another usually by a chemical neurotransmitter
Myelin Sheath
encloses the axon
the plasma membrane surrounding a Schwann cell of a myelinated nerve fiber and separating layers of myelin
Nodes of Ranvier
gaps or indentations in the myelin sheath
small collections of cell bodies found in a few sites outside the CNS in the PNS
bundles of nerve fibers running through the CNS (tracts) in the PNS (nerves)
White Matter
consists of dense collections of myelinated fibers
Gray Matter
contains mostly of unmyelinated fibers and cell bodies
Association or Interneurons
third category of neurons. They connect the motor and sensory neurons in neural pathways
there are fewer positive ions sitting on the inner face of the neuron's plasma membrane than there are on its outer face in the tissue fluid that surrounds it
inward rush of sodium ions that changes the polarity of the neuron's membrane at the site
Action Potential
a long distance signal. The change in electrical potential that occurs between the inside and outside of a nerve or muscle fiber when it is stimulated, serving to transmit nerve signals
outflow of positive ions from the cell restores the electrical conditions at the membrane to the polarized or resting state
are rapid, predictable, and involuntary responses to stimuli
Autonomic Reflexes
regulate the activity of smooth muscles, the heart, and glands
Somatic Reflexes
include all reflexes that stimulate the skeletal muscles