Fundamentals of the Nervous System
Organization and Core Concepts
Start with the division of the nervous system into central (brain, spinal cord) and peripheral components, then the peripheral split into somatic and autonomic, and the autonomic split into sympathetic and parasympathetic. Know the functional unit: the neuron with dendrites, soma, axon, and terminals, and the supporting cells - astrocytes (blood-brain barrier, glutamate uptake), oligodendrocytes (CNS myelin), Schwann cells (PNS myelin), microglia (immune surveillance), and ependymal cells (CSF production and flow).
Understand resting membrane potential (about -70 mV, set largely by potassium permeability), the sodium-potassium pump, and how depolarization to threshold opens voltage-gated sodium channels to generate an action potential. Saltatory conduction in myelinated fibers is faster and more energy-efficient. Synaptic transmission is chemical: calcium influx triggers vesicle release, neurotransmitter binds receptors, and termination occurs by reuptake or enzymatic breakdown. Know the major transmitters - acetylcholine, dopamine, norepinephrine, serotonin, GABA (inhibitory), and glutamate (excitatory).
Traps
Questions often swap oligodendrocytes and Schwann cells, or ask which cell makes CSF (ependymal, not choroid plexus alone). A common distractor claims myelin speeds conduction by increasing the action potential amplitude - it actually increases conduction velocity by restricting current flow between nodes. Another trap confuses the direction of sympathetic versus parasympathetic effects on a single organ.
Rule of Thumb
"One neuron, one axon, many dendrites; myelin = speed." When a stem asks what happens if myelin is lost, answer demyelination slows or blocks conduction (as in multiple sclerosis in the CNS).