Neuroanatomy 2: Cellular Structure of the CNS

Vocabulary flashcards summarizing the key cellular components, structures, and supporting elements of the central and peripheral nervous systems, along with disease-related terms mentioned in the lecture.

Neuron

Electrically excitable, terminally differentiated cell that processes and transmits information; composed of soma, dendrites, and axon.

Glial cells

Non-neuronal support cells of the nervous system, including astrocytes, oligodendrocytes, Schwann cells, and microglia.

Astrocyte

Star-shaped macroglial cell that maintains neurotransmitter and ion homeostasis, supports metabolism, contributes to the blood-brain barrier, and regulates cerebral blood flow.

Oligodendrocyte

Myelinating glial cell of the CNS; each wraps segments of several axons with myelin.

Schwann cell

Myelinating glial cell of the PNS; each wraps one axon segment with myelin.

Microglia

Resident immune cells of the CNS that act as phagocytes, respond to injury, and help prune synapses.

Soma (cell body)

Metabolic center of a neuron containing nucleus, Nissl bodies, and most protein-synthesis machinery.

Dendrite

Branched neuronal process that receives synaptic inputs (‘input’ region).

Axon

Long neuronal process that conducts action potentials and delivers output to synaptic terminals.

Synapse

Specialized junction where an axon terminal communicates with another cell via neurotransmitter release.

Axonal transport

Microtubule-based movement of organelles and proteins between soma and distal axon/dendrites.

Nissl bodies

Aggregates of rough endoplasmic reticulum and ribosomes in neuron soma indicating high protein synthesis.

Cytoskeleton

Internal scaffolding of neurons composed of actin filaments, intermediate filaments, and microtubules.

Actin filament

Dynamic cytoskeletal element important for growth cones, dendritic spines, and cell motility.

Intermediate filament (neurofilament)

Stable cytoskeletal component in all neuronal processes that provides mechanical strength.

Microtubule

Tubulin polymer running along axons and dendrites; supports structural polarity and axonal transport.

Highly polarized neuron

Feature where dendrites receive input and the axon provides output, creating directional signaling.

Graded potential

Small, decremental change in membrane voltage that spreads passively through dendrites and soma.

Action potential

Rapid, all-or-none electrical impulse that propagates along axons for long-distance communication.

Na⁺/K⁺-ATPase pump

Membrane protein that maintains ionic gradients by actively exporting Na⁺ and importing K⁺.

Myelin sheath

Multilayered lipid-rich wrapping formed by oligodendrocytes or Schwann cells that electrically insulates axons and speeds conduction.

Node of Ranvier

Gap between myelin segments where action potentials are regenerated by clusters of voltage-gated channels.

Peripheral nerve

Bundle of axons in the PNS enclosed by connective tissue layers (endoneurium, perineurium, epineurium).

Fascicle

Sub-bundle of nerve fibers within a peripheral nerve surrounded by perineurium.

Perineurium

Collagenous connective tissue sheath encasing each fascicle of a peripheral nerve.

Epineurium

Outer connective tissue layer that encloses multiple fascicles and blood vessels in a peripheral nerve.

Ganglion

Collection of neuronal cell bodies located outside the CNS.

Sensory (dorsal root) ganglion

Peripheral ganglion housing cell bodies of primary sensory neurons.

Autonomic ganglion

Peripheral ganglion containing cell bodies of post-ganglionic autonomic neurons.

Choroid plexus

Vascularized epithelial tissue within brain ventricles that produces cerebrospinal fluid (CSF).

Ventricular system

Network of brain cavities (ventricles) filled with cerebrospinal fluid.

Cerebrospinal fluid (CSF)

Clear fluid produced by the choroid plexus that cushions the CNS and removes metabolic waste.

Blood-brain barrier (BBB)

Selective barrier formed mainly by tight junctions of brain capillary endothelial cells that restricts substance passage into the CNS.

Lewy body

Intracytoplasmic aggregate of α-synuclein found in degenerating neurons, characteristic of Parkinson’s disease.

Substantia nigra

Midbrain nucleus whose dopaminergic neuron loss leads to Parkinsonian motor symptoms.

Terminally differentiated cell

Cell that has permanently exited the cell cycle and no longer divides, such as mature neurons.