Key Terms
Two systems run the show
The nervous system (electrical) and the endocrine system (chemical). Understand those two systems and you understand the
Nervous system
100+ billion specialized cells transmitting information throughout the body.
CNS (Central Nervous System)
Brain + spinal cord. The command center.
PNS (Peripheral Nervous System)
Neurons linking CNS to skin, muscles, glands. Endocrine system: glands that secrete hormones.
Neuron
A cell that receives and transmits information.
Terminal buttons
Tips at the end of axon branches; release neurotransmitters.
Myelin sheath
Fatty insulation on axon; speeds signal.
Nodes of Ranvier
Gaps in myelin; action potential jumps between them.
Resting potential
Neuron's default negative charge state.
Action potential
Electrical charge change that fires down the axon when threshold is crossed.
All-or-nothing principle
The neuron either fires completely or not at all. It cannot fire more strongly; it can only fire faster.
Refractory period
Recovery time after neuron fires; cannot fire again yet.
Synapse
Gap between terminal button and next neuron's dendrite.
Neurotransmitter
Chemical crossing synapse to communicate between neurons.
Excitatory effect
Makes the receiving neuron more likely to fire.