Neuron
A nerve cell; the basic building block of the nervous system
Dendrite
A neuron’s bushy, branching extensions that receive messages & conduct impulses towards the cell body
Axon
The neurons extension that passes messages through its branches to other neurons or to muscles or glands.
Myelin Sheath
A fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next
Glial Cells
Cells in the nervous system that support, nourish & protect neurons; they may also play a role in learning, thinking & memory
Action Potential
A neural impulse; a brief electrical charge that travels down an axon
Refractory Period
A period of inactivity after a neuron has fired
Synapse
The junction between the axon tip of the sending neuron & the dendrite or cell body of the receiving neuron
Neurotransmitters
Chemical messengers that cross the synaptic gaps between neurons
Reuptake
A neurotransmitter’s reabsorption by the sending neuron
Endorphins
“morphine within” – natural, opiate-like neurotransmitters linked to pain control & to pleasure
Agonist
A molecule that increases a neurotransmitter’s action
Antagonist
A molecule that inhibits, or blocks, a neurotransmitter’s action