Systems Neurobiology & Sensory Systems Review

Vocabulary practice flashcards covering synapses, neurotransmitters, autonomic and central nervous system divisions, sensory coding, vision, hearing, balance, touch, olfaction, and gustation based on the lecture notes.

En passant synapse

A synaptic arrangement where communication occurs along the length of an axon rather than exclusively at its terminal end.

Synaptotagmin

A presynaptic protein that binds entering $Ca^{2+}$ and interacts with SNARE proteins to trigger synaptic vesicle fusion with the plasma membrane.

SNARE proteins

Proteins that interact with activated synaptotagmin to mediate synaptic vesicle fusion and exocytosis of neurotransmitters.

Ionotropic receptor

A receptor protein that functions directly as an ion channel, opening or closing upon ligand binding to produce fast electrical responses.

Metabotropic receptor

A G-protein-coupled receptor (GPCR) that regulates cellular functions indirectly through intracellular second-messenger pathways.

Nicotinic ACh receptor

An ionotropic, nonspecific cation channel activated by acetylcholine and nicotine that conducts $Na^+$, $K^+$, and sometimes $Ca^{2+}$ to produce fast excitatory postsynaptic effects.

Muscarinic ACh receptor

A metabotropic GPCR activated by acetylcholine that operates via second messengers, classified into $G_q$-linked ($M_1$, $M_3$, $M_5$) and $G_i$-linked ($M_2$, $M_4$) subtypes.

$\alpha_1$-Adrenergic receptor

A metabotropic GPCR coupled to $G_q$ and PLC, located on smooth muscle of skin and gut blood vessels, that mediates vasoconstriction.

$\alpha_2$-Adrenergic receptor

A metabotropic GPCR coupled to $G_i$ on adrenergic axon terminals that inhibits adenylyl cyclase, lowers $cAMP$, and reduces norepinephrine release.

$\beta_1$-Adrenergic receptor

A metabotropic GPCR coupled to $G_s$ located primarily in the heart that increases $cAMP$ to elevate heart rate and contraction strength.

$\beta_2$-Adrenergic receptor

A metabotropic GPCR coupled to $G_s$ on blood vessels supplying the heart and skeletal muscle that increases $cAMP$ to mediate vasodilation.

Nuclei

Clusters or groups of neuronal cell bodies located inside the central nervous system (CNS).

Ganglia

Clusters or groups of neuronal cell bodies located inside the peripheral nervous system (PNS).

Dorsal root ganglion

A PNS ganglion located near the spinal cord that contains the cell bodies of somatosensory (afferent) neurons.

DAVE mnemonic

A memory rule for spinal cord roots indicating that Dorsal is Afferent and Ventral is Efferent.

Primary motor cortex

A frontal lobe cortical region responsible for executing discrete, voluntary skeletal muscle movements on the contralateral side of the body.

Premotor cortex

A frontal lobe cortical region responsible for planning and coordinating complex motor patterns among groups of muscles.

Thalamus

A forebrain relay station that filters, sorts, and routes sensory information to appropriate regions of the cerebral cortex.

Pupil

An anatomical hole or opening in the center of the iris whose size is dynamically regulated by circular and radial smooth muscle contraction.

Chromaffin cells

Modified postganglionic-like cells in the adrenal medulla that release epinephrine into the bloodstream upon receiving ACh from preganglionic sympathetic neurons.

Generator potential

A graded potential formed directly within the dendritic membrane of a primary sensory neuron.

Receptor potential

A graded potential formed in a separate specialized receptor cell that must then signal to an adjacent afferent neuron.

Adequate stimulus

The specific modality of stimulus energy to which a given sensory receptor exhibits its lowest threshold and highest sensitivity.

Lateral inhibition

A sensory processing mechanism in which strongly active central pathways suppress neighboring pathways to enhance contrast and spatial acuity.

Dynamic range

The total span of stimulus intensities over which a sensory receptor varies its action-potential firing rate between threshold and saturation.

Range fractionation

An organizational principle in which individual receptors cover distinct, overlapping slices of an intensity spectrum to give the entire sensory system a broad dynamic range with precise discrimination.

Tonic receptors

Slowly adapting sensory receptors that produce continuous action potential firing for the entire duration of a sustained stimulus.

Phasic receptors

Rapidly adapting sensory receptors that fire action potentials primarily at the onset, offset, or during rapid changes of a stimulus.

Ciliary photoreceptor pathway

The visual transduction system in rods and cones where light converts 11-cis retinal to all-trans retinal, activating transducin ($G_i$) and PDE to lower $cGMP$, close CNG channels, and hyperpolarize the cell.

Accommodation

The process where ciliary muscle contraction slackens suspensory ligaments, allowing the lens to bulge into a rounded shape to focus light from nearby objects onto the retina.

Fovea centralis

A specialized central retinal area containing exclusively cones, no overlying blood vessels, and minimal neural convergence, optimized for maximum visual acuity.

Endolymph

The specialized fluid bathing hair-cell stereocilia that contains an exceptionally high concentration of $K^+$, driving $K^+$ influx and cell depolarization when mechanically gated cation channels open.

Maculae

Sensory structures in the utricle and saccule containing hair cells that detect linear acceleration and head position relative to gravity.

Cristae

Sensory structures housed within the ampullae of the semicircular canals that contain hair cells designed to detect angular or rotational acceleration.

Outer hair cells

Auditory receptor cells that exhibit somatic electromotility to mechanically amplify basilar-membrane oscillations and enhance signal detection by inner hair cells.

Pacinian corpuscle

A rapidly adapting mechanoreceptor with a large, vague receptive field that produces generator potentials in response to vibration.

Merkel disk

A slowly adapting mechanoreceptor with a small, sharp receptive field that produces receptor potentials in response to sustained touch.

Combinatorial coding

An olfactory encoding system where individual odorants activate distinct combinations of GPCR types, allowing the brain to distinguish diverse odors from overlapping receptor patterns.

Olfactory glomeruli

Structures in the olfactory bulb where axon terminals of olfactory receptor neurons expressing the exact same receptor GPCR converge onto postsynaptic target cells.

ENaC channels

Epithelial sodium channels through which $Na^+$ directly enters salty-taste receptor cells to cause cell depolarization.

Otop1 proton channels

Transmembrane channels through which $H^+$ enters sour-taste receptor cells, lowering intracellular pH to inhibit $K^+$ channels and depolarize the cell.

Suprachiasmatic nucleus (SCN)

A hypothalamic nucleus serving as the primary master pacemaker for endogenous circadian rhythms.

Long-term potentiation (LTP)

A long-lasting increase in synaptic efficacy resulting from high-frequency synaptic stimulation in the hippocampus, serving as a cellular model for learning and memory.