Unit 3 Vocab Part 1

Neuron

a nerve cell; the basic building block of the nervous system

cell body

the part of a neuron that contains the nucleus; the cell's life-support center

Dendrites

a neuron's often bushy, branching extensions that receive and integrate messages, conducting impulses toward the cell body.

axon

the neuron extension that passes messages through its branches to other neurons or to muscle 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, and protect neurons; they also play a role in learning, thinking, and memory

action potential

a neural impulse; a brief electrical charge that travels down an axon

Threshold

the level of stimulation required to trigger a neural impulse

refractory period

in neural processing, a brief resting pause that occurs after a neuron has fired

all-or-none response

a neuron's reaction of either firing or not firing

synapse

the junction between the axon tip of the sending neuron and 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, opiatelike neurotransmitters linked to pain control and to pleasure.

agonist

a molecule that increases a neurotransmitter's action

antagonist

a molecule that inhibits or blocks a neurotransmitter's action