neuron
cell specialized to receive and transmit info to other cells in the body; aka a nerve cell; bundles of many are called nerves
sensory neuron
nerve cells that carry messages from sense receptors to the central nervous system; aka afferent neuron
motor neuron
nerve cell that carries messages away from the central nervous sysytem to the muscles and glands; aka efferant neuron
interneuron
nerve cell that relays messages between other nerve cells
dendrite
branched fiber that extends outward from the main cell body and carries info into the neuron
soma
part of the neuron containing the nucleus, which includes the chromosomes; aka the cell body
axon
extended fiber that conducts info from the soma to the axon terminals; info travels in the form of an electrical charge
synaptic vesicle
small "container" holding neurotransmitter molecules that then connect to the presynaptic membrane, releasing the neurotransmitters into the synapse
neurotransmitter
chemical messengers that relay messages across the synapse (many are also hormones); they fit the shape of the receptor site in the membrane of the target cell, they stimulate the receiving neuron and carry the message forward
glial cells
produce the myelin sheath of the axon; located w/in the sheath
myelin sheath
the insulating covering that facilitates electrical impulses in the neuron
node of Ranvier
one of the many gaps in the myelin sheath; this is where the action potential occurs
axon terminal
aka "terminal buttons"; structures at the end of the axon that carry the neuron's message into the synapse
synapse
a gap that serves as a communication link between neurons; also occur between neurons and the muscles and glands they serve
synaptic transmission
the relaying of info across the synapse by means of neurotransmitters
resting potential
the electrical charge of the axon in its inactive state, when the neuron is ready to "fire"; ions w/in the cell have a negative charge at this time
action potential
when the cell body becomes excited the charge is temporarily reversed (to positive) and causes and electrical signal to race along the axon
all-or-none principle
an axon either fires or it doesn't; there is no halfway about action potential