Foundations of Behavioral Neuroscience and Sensory Systems

Comprehensive vocabulary flashcards covering neuroanatomy, neurophysiology, chemical signaling, brain development, sensorimotor function, hearing, chemical senses, and vision.

Input Zone

The part of a neuron, primarily consisting of dendrites and the cell body, where neurons collect and integrate information from the environment or from other cells.

Axon Hillock

A cone-shaped area of the neuronal cell body that gives rise to the axon and converts incoming input into electrical signals that travel down the axon.

Oligodendrocytes

A type of glial cell that wraps around axons to form the insulating myelin sheaths in the central nervous system (brain and spinal cord).

Astrocytes

Star-shaped glial cells with processes that stretch around and between neurons and blood vessels, secrete chemicals, and help form the outer membrane around the brain.

Microglial Cells

Tiny, mobile glial cells that remove debris from injured or dead cells by engulfing and destroying them.

Autonomic Nervous System

The division of the peripheral nervous system consisting of nerves that connect to the viscera (internal organs), further divided into the sympathetic and parasympathetic divisions.

Corpus Callosum

A large bundle of axons that connects the left and right cerebral hemispheres, allowing communication between them.

Basal Ganglia

A group of interconnected subcortical forebrain nuclei—primarily the caudate nucleus, putamen, and globus pallidus—crucial for motor control and movement initiation.

Connectome

The comprehensive network map describing all functional connections and axonal pathways among distinct brain regions.

Meninges

The three protective membranes surrounding the brain and spinal cord: the dura mater, arachnoid membrane (filled with cerebrospinal fluid), and pia mater.

Resting Potential

The difference in electrical potential across the neural membrane at rest, typically ranging from $-50\,\text{mV}$ to $-80\,\text{mV}$, indicating that the interior of the cell is more negative than the exterior.

Sodium-Potassium Pump

An active transport mechanism that maintains resting potential by expelling three sodium ions ($3\,\text{Na}^+$) out of the neuron for every two potassium ions ($2\,\text{K}^+$) pumped inside.

Absolute Refractory Phase

The brief period immediately following an action potential during which voltage-gated $\text{Na}^+$ channels are inactivated and no stimulus, no matter how strong, can trigger another action potential.

Saltatory Conduction

The rapid form of action potential propagation along a myelinated axon, where the depolarization jump from one Node of Ranvier to the next.

Excitatory Postsynaptic Potential (EPSP)

A small, local depolarizing potential in the postsynaptic membrane produced when positive ions like $\text{Na}^+$ enter the cell, increasing the likelihood of reaching threshold and firing an action potential.

Inhibitory Postsynaptic Potential (IPSP)

A local hyperpolarizing potential in the postsynaptic membrane produced primarily by the influx of chloride ions ($\text{Cl}^-$), moving the membrane potential farther away from threshold.

Spatial Summation

The integration of postsynaptic potentials arriving simultaneously from different physical synaptic locations across the cell body and dendrites at the axon hillock.

Temporal Summation

The summation of postsynaptic potentials that arrive at the axon hillock closely spaced in time from the same input source.

Types of Synaptic Connections

Variations of chemical synapses classified by their junction sites: axo-dendritic (axon to dendrite), axo-somatic (axon to soma), axo-axonic (axon to axon), and dendro-dendritic (dendrite to dendrite).

Ionotropic Receptors

Receptor proteins containing a ligand-gated ion channel that directly and rapidly open or close when a neurotransmitter binds to them.

Metabotropic Receptors

Receptor proteins that do not contain an intrinsic ion channel but alter cellular chemistry by activating G proteins and second-messenger cascades upon transmitter binding.

Mesostriatal Pathway

A major dopaminergic pathway originating in the substantia nigra of the midbrain and projecting to the striatum/basal ganglia, essential for motor control and degenerated in Parkinson's disease.

Mesolimbocortical Pathway

A dopaminergic pathway originating in the ventral tegmental area (VTA) and projecting to the nucleus accumbens and cortex, crucial for positive reinforcement and reward processing.

Effective Dose 50% ($\text{ED}_{50}$)

The drug dose that produces half ($50\%$) of the compound's maximal observed physiological or behavioral effect on a dose-response curve.

Functional Tolerance

Decreased drug responsiveness caused by target tissue modifications, such as down-regulation (fewer receptors in response to an agonist) or up-regulation (more receptors in response to an antagonist).

Cell Differentiation

The developmental stage where precursor cells express specific sets of genes to acquire the distinctive structure and function of specialized neurons or glial cells through cell-cell interactions.

Apoptosis

Genetically programmed selective cell death occurring naturally during neural development as neurons compete for synaptic sites and neurotrophic factors.

Hebbian Synapse

A synapse that is strengthened when it successfully drives the postsynaptic cell to fire, or weakened and eliminated if its activity fails to drive the postsynaptic target.

Epigenetics

The study of stable changes in gene expression and cellular function—such as DNA methylation—that do not involve alterations to the underlying DNA nucleotide sequence.

Sensory Transduction

The biophysical process by which external physical stimuli (such as light, sound, mechanical touch, or chemicals) are converted into electrical changes across a receptor cell membrane.

Cutaneous Mechanoreceptors

Sensory receptors embedded in the skin including Pacinian corpuscles (vibration and texture), Meissner's corpuscles (light touch), Merkel's discs (edges and isolated points), and Ruffini corpuscles (stretch).

Sensory Adaptation

The progressive decrease in a receptor cell's firing frequency in the presence of continuous, unchanging stimulation, distinguishing phasic receptors from tonic receptors.

Primary Somatosensory Cortex (S1)

A region located in the postcentral gyrus of the parietal lobe that receives somatotopically organized tactile information from the contralateral side of the body.

Anterolateral System

A somatosensory pathway (also called the spinothalamic system) whose nerve fibers enter the dorsal horn of the spinal cord, cross the midline, and ascend to the thalamus conveying pain and temperature signals.

Muscle Spindle

A encapsulated sensory proprioceptor containing intrafusal muscle fibers lying parallel to skeletal muscle fibers, sensitive to muscle stretch and changes in muscle length.

Golgi Tendon Organ

A proprioceptor located in the tendon at the muscle-bone junction that monitors mechanical tension exerted during muscle contraction.

Mirror Neurons

Specialized neurons located in premotor cortex subregion F5 that discharge both when an individual executes a motor act and when observing another individual perform the same action.

Organ of Corti

The central auditory structure situated on the basilar membrane within the cochlea containing sensory inner and outer hair cells that transduce sound vibrations into neural activity.

Tonotopic Organization

The systematic spatial arrangement of auditory neurons and pathways according to the sound frequencies to which they respond maximally, progressing from low to high frequencies.

Semicircular Canals

Three fluid-filled bony tubes aligned in orthogonal planes of motion (nodding/pitch, shaking/yaw, and tilting/roll) that detect angular acceleration and head rotation.

Glomerulus (Olfactory)

A spherical synaptic structure in the olfactory bulb where axon terminals from olfactory receptor cells expressing the exact same odorant receptor subtype converge onto mitral cells.

Scotopic System

The rod-dominated visual system characterized by high sensitivity to dim light, absence of color detection, low spatial acuity, and high prevalence in the retinal periphery.

Photopic System

The cone-dominated visual system operating at higher illumination levels that provides sharp visual acuity and mediates wavelength-dependent color perception.

Fovea

The central depression in the retina packed densely with small cones and free of overlying blood vessels or cell layers, producing maximum visual acuity.

Lateral Inhibition

The phenomenon whereby interconnected sensory neurons (such as retinal horizontal and bipolar cells) inhibit their neighbors, sharpening boundaries and enhancing visual edge contrast.

Visual Processing Streams

Two cortical pathways originating from primary visual cortex (V1): the dorsal stream ('where') projecting to parietal cortex to guide motion and spatial localization, and the ventral stream ('what') projecting to inferior temporal cortex for object and face recognition.