What are the two main cell types of the nervous system?
Neurons (signal transmission) and glia (support).
Who debated whether neurons or networks were the basic unit of the nervous system?
Camillo Golgi (nerve net/reticular theory) vs. Santiago Ramón y Cajal (neuron theory).
What did Golgi contribute?
The Golgi stain (silver nitrate method), showing a “nerve net.”
What did Cajal contribute?
Neuron theory: nervous system made up of discrete cells (neurons).
What structure allows direct neuron-to-neuron electrical communication?
Gap junctions (electrical synapses).
What are dendrites?
Branches off soma that increase surface area and collect information.
What is the soma (cell body)?
Core region containing nucleus and organelles; main site of protein synthesis.
What is the axon?
Singular extension from soma that carries messages to other neurons.
What is the axon hillock?
Junction of soma and axon; integration and initiation site of action potentials.
What are axon collaterals?
Branches of an axon.
What are telodendria?
Terminal branches of an axon.
What are terminal buttons (end feet)?
Knobs at axon tips that transmit signals to other neurons.
What is a synapse?
Junction between neurons where information is transferred.
What is the presynaptic membrane?
Output side (axon terminal membrane).
What is the postsynaptic membrane?
Input side (usually a dendritic spine).
What is the axon initial segment (AIS)?
Site where action potentials are typically initiated.
What are the three functional classes of neurons?
Sensory neurons – carry input into CNS
Interneurons – association neurons within CNS
Motor neurons – carry output to muscles/glands
What is the morphology of sensory neurons?
Often pseudounipolar or bipolar.
What is the morphology of interneurons?
Multipolar; make up most of mammalian brain neurons.
What is the morphology of motor neurons?
Large, multipolar; located in brainstem and spinal cord.
How do neurons “decide” whether to fire?
By summing excitatory and inhibitory inputs.
What property underlies brain plasticity?
Dendritic spines can be added or pruned.
What are glial cells?
“Glue” cells that support neurons structurally, nutritionally, immunologically, and by insulating axons.
What do astrocytes do?
Provide structural support, regulate blood-brain barrier, maintain extracellular environment, regulate synaptic transmission (tripartite synapse).
