| A | B |
|---|
| peripheral nervous system | all neurons that have extensions outside the brain and spinal cord |
| autonomic nervous system | PNS neurons that are not conscious and control internal organs |
| neuron | the basic unit of communication within the nervous sytem |
| dendrite | extension of a neuron that receives information from other neurons |
| synapse | the junction of a neuron with another neuron or muscle cell |
| reflex | a sudden involuntary response to a stimulus |
| myelin sheath | insulating cells that surround neuron axons |
| potassium ions | ions that are found more concentrated inside a resting neuron |
| neurotrasmitters | chemicals that carry messages across the synapse |
| brainstem | has nerves that control breathing, swallowing, heartbeat, and the diameter of blood vessels |
| synaptic cleft | gap between neurons |
| action potential | a wave of depolarization that can be caused by electrical shock |
| sodium ions | there are more of these outside a neuron than in |
| sympathetic nervous system | prepares the body for threats |
| parasympathetic nervous system | relaxes the body when a threat has passed |
| sensory neurons | transport messages from the outside to the CNS |
| motor neurons | transport messages from the CNS to muscles and glands |
| resting potential | a neuron ready to "fire" |
| Nodes of Ranvier | gaps between myelin sheath cells |
| sodium-potassium pump | actively transports 3 Na+ outside and 2 K+ inside |
