The Nervous System: Neuronal Structure, Glia, and Conduction

Vocabulary flashcards covering cellular neuroanatomy, glial cell types, membrane potentials, transport mechanisms, and neuronal conduction.

Neural Net Hypothesis

A hypothesis advocated by Camillo Golgi stating that the nervous system is composed of a continuous mass of tissue.

Neuron Doctrine

A theory proposed by Santiago Ramón y Cajal asserting that neurons are individual cells that form the basic functional units of the nervous system.

Cytoskeleton

The internal structural framework of a neuron, consisting of microtubules ($20\,nm$), neurofilaments ($10\,nm$), and microfilaments ($5\,nm$).

Dendritic Spines

Small protrusions on dendrites that increase surface area for receiving synaptic input and can dynamically change shape.

Axon Hillock

The region where the axon joins the cell body; functions as the spike initiation zone where postsynaptic potentials summate to determine if an action potential is triggered.

Transcription

The cellular process occurring in the nucleus in which DNA is copied to produce a messenger RNA (mRNA) transcript.

Translation

The cellular process in the cytoplasm where ribosomes decode mRNA to assemble newly created proteins.

Anterograde Transport

Form of axoplasmic transport moving materials along microtubules from the cell body (soma) forward to the axon terminal using kinesin motor proteins.

Retrograde Transport

Form of axoplasmic transport moving materials backwards from the axon terminal to the cell body (soma) using dynein motor proteins.

Astrocytes

Star-shaped glial cells that provide physical support, maintain the extracellular chemical environment, perform phagocytosis, fill space, and supply nutrients.

Microglia

Glial cells in the central nervous system that serve immune functions and perform phagocytosis to clear cellular debris.

Oligodendrocytes

Glial cells responsible for producing the myelin sheath around axons located within the Central Nervous System (CNS).

Schwann Cells

Glial cells responsible for providing myelin sheaths around neuronal axons in the Peripheral Nervous System (PNS).

Cation

A positively charged ion, such as sodium ($Na^+$), potassium ($K^+$), or calcium ($Ca^{2+}$).

Anion

A negatively charged ion, such as chloride ($Cl^-$) or cellular organic anions ($A^-$).

Diffusion

The passive movement of ions along a concentration gradient from an area of higher concentration to an area of lower concentration.

Electrostatic Force

The electrical gradient force acting on ions where like charges repel each other and opposite charges attract.

Resting Membrane Potential

The difference in electrical charge across the cell membrane at rest, typically $-65\,mV$ to $-70\,mV$, with the inside of the neuron more negative than the outside.

Sodium-Potassium Pump

A membrane transporter protein that maintains the resting membrane potential by actively pumping $3\,Na^+$ ions out of the cell for every $2\,K^+$ ions pumped in.

Depolarization

A change in membrane potential that makes the inside of the cell less negative relative to the outside.

Hyperpolarization

A change in membrane potential that makes the inside of the cell more negative relative to the outside.

Excitatory Postsynaptic Potential (EPSP)

A graded depolarization of the postsynaptic membrane that decays in strength as it travels toward the axon hillock.

Inhibitory Postsynaptic Potential (IPSP)

A graded hyperpolarization of the postsynaptic membrane that decays in strength as it travels toward the axon hillock.

Spatial Summation

The integration of postsynaptic potentials arriving simultaneously from multiple different presynaptic inputs at different locations on a neuron.

Temporal Summation

The integration of multiple postsynaptic potentials generated in rapid succession from a single presynaptic neuron over time.

Action Potential

A rapid, all-or-none electrical pulse generated along an axon when the threshold of excitation is reached, propagating without losing strength.

Saltatory Conduction

The rapid mechanism of action potential propagation along a myelinated axon, where the signal leaps from one node of Ranvier to the next.

Nodes of Ranvier

Unmyelinated gaps along a myelinated axon where action potentials are regenerated.