AANN Core Curriculum, 7th Edition, Ch. 2 Cellular Physiology of the Nervous System: Digital Version-Chapter 2

Chapter 2
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The nervous system coordinates cognition, movement, sensory processing, and homeostasis through neurons and supporting glial cells.<br /><br />Neurons receive signals through dendrites, process them in the cell body, and transmit action potentials along axons to terminals, where neurotransmitters communicate with other cells. Their cytoskeleton supports cell shape and intracellular transport; myelin speeds axonal signaling. Functionally, neurons are sensory (afferent), motor (efferent), or interneurons. Structurally, they may be multipolar, bipolar, or pseudounipolar; by axon length, they are classified as Golgi I (long projection) or Golgi II (short or absent axon).<br /><br />Glia support neuronal function. Astrocytes nourish neurons, regulate synapses, and help maintain the blood–brain barrier (BBB). Oligodendrocytes form myelin in the central nervous system; Schwann cells perform this role in the peripheral nervous system. Microglia provide immune defense and remove debris, while ependymal cells line brain ventricles and the spinal canal and help circulate cerebrospinal fluid.<br /><br />The nervous system develops from the embryonic ectoderm, which forms the neural plate and then the neural tube. The tube gives rise to the brain and spinal cord, while neural crest cells form many peripheral nervous system structures. Neurons and connections grow, differentiate, and are later selectively pruned; genetic signals and growth factors guide these processes.<br /><br />At rest, a neuron has a negative membrane potential. Sufficient stimulation opens voltage-gated sodium channels, producing an action potential, followed by potassium-driven repolarization and a brief refractory period. Signals travel along axons and cross synapses either directly through electrical gap junctions or chemically. In chemical transmission, calcium entry triggers neurotransmitter release; the transmitter binds receptors on the next cell and is then cleared or recycled.<br /><br />Neurotransmitters include catecholamines (arousal, sympathetic responses, movement, and reward), acetylcholine (muscle activation, attention, and memory), serotonin (mood, sleep, and pain), histamine (cognition and bodily regulation), GABA and glycine (mainly inhibitory), and glutamate (mainly excitatory; learning and memory). Neuropeptides modulate signaling and include endorphins (pain relief), CRH (stress), and oxytocin (social and autonomic effects).<br /><br />The BBB’s tight endothelial junctions, supported by astrocytes and pericytes, limit harmful blood substances while selectively allowing nutrients such as glucose and gases to reach the brain.
Keywords
nervous system
neurons
glial cells
action potential
synapses
myelin
blood-brain barrier
neurotransmitters
astrocytes
embryonic development