Neurobiology: Glia, Action Potentials, Neurotransmission, and Neurodegenerative Pathology

Vocabulary practice flashcards covering glial function, neural signaling, action potential propagation, synaptic receptor physiology, prion pathology, and the molecular genetics of Alzheimer's disease.

Astrocytes

Star-shaped glial cells that provide structural and chemical support for neurons and contribute to the formation of the blood-brain barrier (BBB).

Oligodendrocytes

Glial cells responsible for producing and maintaining the insulating myelin sheath surrounding axons in the central nervous system (CNS).

Schwann Cells

Glial cells that provide the myelin sheath for axons located in the peripheral nervous system (PNS).

Microglial Cells

Specialized immune cells of the brain that can exacerbate preexisting inflammation and contribute to cell death in pathologies such as Alzheimer's disease.

$\beta$-Amyloid Plaques

Extracellular pathological aggregates composed of insoluble $\beta$-amyloid protein paired with apolipoprotein E (apo E), resulting from aberrant proteolytic cleavage of amyloid precursor protein (APP).

Neurofibrillary Tangles

Intracellular fibrillar accumulations characteristic of Alzheimer's disease composed predominantly of hyperphosphorylated paired helical filaments of tau protein.

Amyloidogenic Pathway

The proteolytic processing route of amyloid precursor protein (APP) mediated sequentially by $\beta$-secretase and $\gamma$-secretase, generating neurotoxic, insoluble $A\beta$ peptides.

Apolipoprotein E (apo E) Gene

A susceptibility gene on chromosome 19 associated with Alzheimer's disease, wherein carrying the $\epsilon 4$ allele elevates risk while the $\epsilon 2$ allele confers protection.

Presenilins (PSEN1 and PSEN2)

Catalytic components of the $\gamma$-secretase complex encoded on chromosomes 14 and 1, respectively; deterministic mutations in these genes cause early-onset autosomal dominant Alzheimer's disease.

Prion

A proteinaceous infectious particle lacking nucleic acid that propagates disease by inducing normal $\alpha$-helical proteins to convert into diseased, misfolded $\beta$-sheet isoforms.

Prusiner's Hypothesis

The principle proposing that a misfolded protein acts as the active, primary infectious agent in spongiform encephalopathies and relies strictly on self-templated propagation.

Scrapie

A transmissible spongiform encephalopathy affecting sheep that clinically manifests with behavioral aberrations, tremors, and severe uncoordinated locomotion.

Kuru

A prion disease historically identified among cannibalistic populations in Papua New Guinea, presenting with headache, pathologic laughing, tremors, and profound motor ataxia.

CPEB (Cytoplasmic Polyadenylation Element Binding Protein)

An adaptive, prion-like protein studied by Eric Kandel that undergoes conformational aggregation to stabilize synaptic plasticity by awakening dormant mRNAs.

Resting Membrane Potential

The baseline electrical potential difference across the undisturbed neuronal membrane, typically measured at $-65\,\text{mV}$.

Sodium-Potassium Pump

An integral membrane-associated active transporter that hydrolyzes $\text{ATP}$ to move $\text{Na}^+$ and $\text{K}^+$ against their electrochemical gradients.

Spike-Initiation Zone

The specific region endowed with a high density of voltage-gated sodium channels where action potentials are initiated, located at the axon hillock in pyramidal neurons and at sensory nerve endings in sensory neurons.

Saltatory Conduction

The accelerated propagation of action potentials along myelinated axons achieved as electrical current spreads rapidly from one node of Ranvier to the next.

Electrical Synapse

A neuronal junction characterized by gap junctions that permit direct, bidirectional ionic flux between adjacent cells for instantaneous transmission of excitation.

Ligand-Gated Ion Channels

Transmitter-gated, ionophoric receptor complexes whose integral channel pore opens upon ligand binding, directly mediating rapid ion flux to generate postsynaptic potentials.

G-Protein-Coupled Receptors (GPCRs)

Metabotropic transmembrane receptors that activate heterotrimeric G-proteins to open ion channels via shortcut pathways or stimulate enzymatic intracellular second messenger cascades.