Key Terms
Central Nervous System (CNS)
Brain + spinal cord. Both enclosed in bone.
Somatic Nervous System (SNS)
Conscious perception; voluntary movement of skeletal muscle; also controls skeletal muscle reflexes.
Autonomic Nervous System (ANS)
Involuntary control; cardiac muscle, smooth muscle, and glands; maintains homeostasis. Sweat glands are ANS.
Enteric Nervous System (ENS)
Controls smooth muscle and glands in the digestive tract. It is part of the PNS and largely independent of the CNS.
Gray matter
Regions dominated by cell bodies and dendrites. Mostly unmyelinated.
White matter
Regions dominated by myelinated axons. White color comes from myelin, which is lipid-rich and appears pale.
SENSATION
Detecting stimuli. Sensory receptors register changes in the internal or external environment.
INTEGRATION
Processing. The CNS compares incoming sensory information against memories, emotional state, and prior learning to produ
RESPONSE
Output. Three types of muscle can be controlled: skeletal (voluntary), cardiac (rate), and smooth (digestion, etc.).
Soma (cell body)
Contains nucleus and major organelles.
Dendrites
Branched processes that receive input from other neurons. Information flows IN via dendrites.
Axon
Single process that carries the signal OUT to target cells. One axon per neuron.
Axon hillock / Initial segment
Where the axon emerges from the soma. This is where action potentials are generated.
Axoplasm
Specialized cytoplasm inside the axon.
Myelin sheath
Lipid-rich insulating wrap around the axon, made by glial cells. Speeds signal transmission.