Neuroscience Review: Neurons, Glia, Signals, Synapses, and Sensory Systems

Vocabulary practice flashcards covering fundamental neuroanatomy, cellular neurophysiology, action potentials, synaptic transmission, neurotransmitters, brain organization, and the chemical/visual sensory systems based on the lecture text.

Histology

The microscopic study of the structure of biological tissues.

Nissl stain

A histological stain using basic dyes to color cell nuclei and surrounding clumps of material called Nissl bodies, useful for distinguishing neurons from glia and studying cytoarchitecture.

Cytoarchitecture

The specific arrangement or layout of neuronal cell bodies in different regions of the brain.

Golgi stain

A histological method discovered by Camillo Golgi involving silver chromate solution that darkly stains a small percentage of neurons in their entirety.

Neuron doctrine

The concept, championed by Santiago Ramón y Cajal, stating that individual neurons are the elementary functional units of the nervous system and communicate by contact rather than continuity.

Anterograde transport

The movement of material down the axon from the soma to the axon terminal, mediated by the protein kinesin along microtubules.

Retrograde transport

The movement of material up the axon from the terminal to the soma, mediated by the protein dynein along microtubules.

Astrocyte

The most abundant type of glial cell in the brain, filling space between neurons, regulating extracellular chemical content (such as $\text{K}^+$), and enveloping synaptic junctions.

Oligodendroglial cell

A type of glial cell in the central nervous system that provides myelin sheaths around multiple axons.

Schwann cell

A type of glial cell in the peripheral nervous system that provides a myelin sheath around a single axon.

Node of Ranvier

A periodic interruption in the myelin sheath of an axon where the axonal membrane is exposed and voltage-gated sodium channels are concentrated.

Resting membrane potential

The steady difference in electrical charge across the neuronal membrane when a cell is at rest, typically about $-65\,mV$.

Equilibrium potential

The electrical potential difference across a membrane that exactly balances an ionic concentration gradient, represented as $E_{\text{ion}}$ and calculated using the Nernst equation.

Sodium-potassium pump

An enzyme-driven membrane protein that actively transports internal $\text{Na}^+$ out of the neuron and external $\text{K}^+$ into the neuron against their concentration gradients using ATP.

Action potential

A rapid, all-or-none reversal of the neuronal membrane potential lasting about $2\,msec$, characterized by a rising phase, overshoot, falling phase, and undershoot.

Absolute refractory period

The period of time (about $1\,msec$) following an action potential during which it is impossible to initiate another impulse because voltage-gated sodium channels are inactivated.

Saltatory conduction

The rapid propagation of an action potential along a myelinated axon, where the impulse skips from node of Ranvier to node of Ranvier.

Gap junction

A specialized site where connexons from two adjacent cell membranes combine to form channels that allow ionic current to pass directly between cells, forming an electrical synapse.

Active zone

The actual site of neurotransmitter release on the presynaptic axon terminal membrane, characterized by dense protein accumulations and clustered synaptic vesicles.

Exocytosis

The calcium-dependent process by which a synaptic vesicle fuses with the presynaptic membrane to spill its neurotransmitter contents into the synaptic cleft.

EPSP (Excitatory Postsynaptic Potential)

A transient depolarization of the postsynaptic membrane caused by the presynaptic release of a neurotransmitter.

IPSP (Inhibitory Postsynaptic Potential)

A transient hyperpolarization of the postsynaptic membrane caused by the presynaptic release of a neurotransmitter.

Shunting inhibition

A form of synaptic inhibition where the opening of chloride channels prevents depolarizing current from flowing internally down a dendrite toward the spike-initiation zone.

G-protein-coupled receptor

A membrane-spanning receptor protein with seven alpha helices that activates intracellular G-proteins upon binding a neurotransmitter, leading to second messenger cascades or channel gating.

Dale's principle

The concept stating that a single neuron releases only one neurotransmitter, though many peptide-containing neurons release co-transmitters.

Endocannabinoid

A lipid-soluble retrograde messenger synthesized on demand from postsynaptic membrane lipids that diffuses backward to bind presynaptic CB1 receptors and reduce transmitter release.

Midsagittal plane

The anatomical plane resulting from splitting the brain into equal right and left halves.

Dura mater

The tough, inelastic outermost meningeal layer that surrounds and protects the central nervous system.

Cerebrospinal fluid (CSF)

The clear fluid produced by the choroid plexus in the ventricles that fills the ventricular system and the subarachnoid space.

Thalamus

The large dorsal structure of the diencephalon that acts as the primary relay station, or gateway, for sensory pathways heading to the cerebral cortex.

Hypothalamus

The ventral diencephalic structure lying below the thalamus that controls the autonomic nervous system, regulates visceral functions, and controls hormone release via the pituitary gland.

Neocortex

The multi-layered cerebral cortex unique to mammals, characterized by an outer molecular layer (layer I) and layers containing pyramidal cells.

Tastant

Any chemical stimulus that dissolves in saliva and interacts with taste receptor cells on the tongue.

Glomerulus

A spherical structure in the input layer of the olfactory bulb where primary olfactory receptor axons expressing a specific gene converge and synapse onto second-order neurons.

Pupil

The opening in the center of the iris that allows light to enter the eye and reach the retina.

Fovea

A dark pit in the central retina specialized for high-acuity central vision, characterized by densely packed cone photoreceptors and the lateral displacement of upper cell layers.

Dark current

The steady movement of $\text{Na}^+$ ions into photoreceptor outer segments through cGMP-gated channels that occurs in complete darkness, keeping the photoreceptor depolarized.

Rhodopsin

The light-sensitive photopigment in rod outer segment disk membranes, consisting of the protein opsin prebound to retinal.

Accommodation

The process by which the ciliary muscle contracts, relaxing tension on the zonule fibers and rounding the crystalline lens to increase its refractive power for near objects.

Population coding

A sensory representation scheme where the combined responses of a large number of broadly tuned neurons are used to uniquely specify stimulus properties such as taste or smell.