NEUR200 Exam 2 Comprehensive Review

Vocabulary practice flashcards covering neurotransmission, neuropharmacology, chemical neuroanatomy, cortical organization, spinal systems, reflexes, cranial nerves, and somatosensory touch and pain pathways for NEUR200 Exam 2.

Dale’s Law

The principle stating that a given neuron will consistently release the same neurotransmitter or neurotransmitters at all of its synapses.

Neurotransmitters

Chemical messengers released directly into the synaptic cleft whose actions are restricted to post-synaptic cells that have synapses with the releasing neuron and are relatively short in duration due to rapid reuptake or enzymatic breakdown.

Hormones

Chemical signaling molecules released into the bloodstream that can affect an enormous number of cells throughout the body and have effects that typically linger.

Ionotropic Receptors

Membrane-bound receptors directly coupled to ion channels ($Na^+$, $Cl^-$, $K^+$, $Ca^{2+}$) where neurotransmitter binding opens the channel to produce rapid post-synaptic excitation or inhibition.

Metabotropic Receptors

Slow-acting, membrane-bound receptors coupled to an intracellular G-protein (GPCR) that activates upon ligand binding to initiate intracellular signaling cascades capable of triggering widespread cellular changes.

AMPA Receptor

An ionotropic, ligand-gated glutamate receptor that undergoes a conformational change upon glutamate binding, allowing sodium ($Na^+$) to rush into the cell.

NMDA Receptor

An ionotropic glutamate receptor that is both ligand-gated and voltage-gated.

GABA-A Receptor

An ionotropic receptor that mediates inhibitory transmission; contains an allosteric benzodiazepine binding site where alcohol binds to increase $Cl^-$ influx.

GABA-B Receptor

A metabotropic receptor that can exert both inhibitory and excitatory effects on targets through intracellular signaling cascades.

Endogenous Ligand

A signaling substance or molecule that is naturally produced within the body.

Exogenous Ligand

A substance or drug introduced from an external source that the body does not naturally produce.

Agonist

An exogenous ligand that mimics the endogenous ligand by binding to the exact same receptor site and activating the receptor (e.g., nicotine, THC).

Antagonist

A ligand that binds to a receptor and prevents endogenous molecules from binding to and activating the receptor.

First Generation Antipsychotics

Antipsychotic medications that function as dopamine $D_2$ receptor antagonists and are associated with numerous side effects.

Second Generation Antipsychotics

Antipsychotic medications that block both dopamine $D_2$ and serotonin receptors to reduce both positive and negative symptoms.

Inverse Agonist

A ligand that binds to a receptor and induces physiological effects directly opposite to those produced by the endogenous ligand (e.g., SR141716A).

SR141716A

A pharmacological agent that acts as an inverse agonist at cannabinoid $CB_1$ receptors.

Allosteric Modulator

A ligand that binds to a distinct site on a receptor separate from the endogenous ligand's binding site, positively or negatively altering channel activity (e.g., alcohol).

Uptake Inhibitor / Transport Blocker

A drug that blocks the reuptake transporter of an endogenous ligand, thereby increasing the concentration and duration of the neurotransmitter at the synapse (e.g., cocaine, Prozac).

Mesolimbic Pathway

A dopamine projection originating in the ventral tegmental area (VTA) and targeting the cortex and nucleus accumbens; primarily involved in motivation and historically termed the reward pathway.

Nigrostriatal Pathway

A dopamine pathway originating in the substantia nigra pars compacta (SNc) and projecting to the striatum (caudate/putamen); responsible for generating, initiating, and maintaining voluntary movement.

Norepinephrine

A neurotransmitter that acts on metabotropic receptors, originating primarily from the locus coeruleus in the CNS/brainstem and the adrenal cortex in the PNS, modulating energy, arousal, attention, and mood.

Raphe Nuclei

Brainstem nuclei that contain serotonin-producing cell bodies projecting throughout the brain to regulate sleep, wakefulness, and mood.

Locus Coeruleus

A brainstem nucleus that serves as the primary CNS site of norepinephrine synthesis, sending widespread projections throughout the brain.

Pre-Bötzinger Complex

A hindbrain nucleus that functions as the central pattern generator for breathing.

Superior Colliculus

A midbrain structure that mediates vision-driven reflexive behaviors.

Inferior Colliculus

A midbrain structure that mediates audition-driven (hearing-driven) reflexive behaviors.

Diencephalon

A subcortical division of the forebrain containing the thalamus (relay center), hypothalamus (survival regulation), and pituitary gland (hormone secretion).

Retinotopic Map

An orderly, spatial representation of the retina mapped onto the primary visual cortex of the occipital lobe.

Dorsal Stream

A cortical visual pathway extending from the occipital lobe to the parietal lobe, known as the 'WHERE' or 'WHERE/HOW' pathway.

Ventral Stream

A cortical visual pathway extending from the occipital lobe to the temporal lobe, known as the 'WHAT' pathway.

Somatotopic Map

A point-for-point mapped representation of the human body surface across the somatosensory cortex of the parietal lobe.

Spiny Neurons

Cortical neurons with dendritic spines that are typically glutamatergic, including efferent pyramidal cells (which constitute approximately $75\%$ of cortical neurons) and stellate interneurons.

Aspiny Neurons

Cortical interneurons lacking dendritic spines that function as inhibitory interneurons and release GABA.

Cortical Columns

Vertical functional columns spanning cortical layers within which constituent neurons share similar response properties to sensory stimulus features.

Cortical Layer IV

The main input layer of the cerebral cortex that contains numerous interneurons receiving specific sensory afferents from the thalamus.

Cortical Layer V

A major cortical output layer that sends axons to subcortical structures and the spinal cord; contains exceptionally large pyramidal neurons called Betz cells.

Betz Cells

Large pyramidal projection neurons located in cortical Layer V that extend long axons down into the spinal cord.

Cortical Layer VI

A cortical output layer composed of pyramidal neurons that project axons to the thalamus.

Dermatomes

Segmental cutaneous areas innervated by sensory fibers of individual spinal cord segments, divided into Cervical, Thoracic, Lumbar, and Sacral divisions.

Fast Fatigable Muscle Fibers

Skeletal muscle fibers that generate high force rapidly but fatigue quickly, requiring the recruitment of many motor neurons during vigorous physical activity.

Muscle Spindles

Intramuscular stretch receptors that detect passive muscle stretch and help maintain posture without conscious input from the brain.

Golgi Tendon Organs

Sensory receptors embedded within muscle tendons that monitor and react to muscle contraction.

Pain Withdrawal Reflex

A protective spinal reflex elicited by sudden, sharp pain that stimulates ipsilateral flexor muscles and inhibits ipsilateral extensor muscles to retract the limb without requiring brain input.

Pacinian Corpuscle

A rapidly adapting encapsulated somatosensory receptor that detects mechanical vibration and pressure.

Ruffini’s Corpuscles

Slowly adapting cutaneous mechanoreceptors that detect skin stretch.

Merkel’s Disks

Slowly adapting somatosensory mechanoreceptors responsive to light, static touch.

Free Nerve Endings

Slowly adapting, unencapsulated dendritic somatosensory endings that detect pain and temperature.

Two-Point Discrimination Threshold

The minimum distance necessary between two tactile contact points on the skin for them to be distinguished as two separate points rather than one.

Dorsal Root Ganglia (DRG)

Clusters of sensory neuron cell bodies positioned outside the spinal cord that relay peripheral somatosensory information into the spinal cord.

Dorsal Column System

An ascending somatosensory pathway carrying mild to moderate pressure and touch information; ascends ipsilaterally in the spinal cord and crosses the midline in the medulla.

Spinothalamic System

An ascending somatosensory pathway carrying excessive pressure, temperature, and damaging pain information; crosses the midline immediately at the spinal cord level upon entry.

Ventral Posterior Lateral (VPL) and Ventral Posterior Medial (VPM)

Thalamic relay nuclei through which tactile and nociceptive somatosensory pathways travel before reaching the primary somatosensory cortex.

Descending Pain Modulation

An endogenous analgesic circuit in which the spinothalamic tract signals the periaqueductal gray and raphe nuclei, activating descending neurons that inhibit pain-sensing neurons in the spinal cord.

Local Pain Modulation

The attenuation of pain signaling achieved when non-nociceptive mechanoreceptor axons activate local spinal inhibitory interneurons (e.g., rubbing an injured area).

Cranial Nerve I (Olfactory Nerve)

A purely sensory cranial nerve whose primary function is mediating the sense of smell.

Cranial Nerve II (Optic Nerve)

A purely sensory cranial nerve whose primary function is vision.

Cranial Nerve VIII (Vestibulocochlear Nerve)

A sensory cranial nerve whose primary functions are hearing and the sense of balance.

Cranial Nerve V (Trigeminal Nerve)

A mixed sensory and motor cranial nerve mediating somatic sensation from the face, mouth, and cornea, as well as innervating the muscles of mastication.

Cranial Nerve VII (Facial Nerve)

A mixed cranial nerve that controls muscles of facial expression, transmits taste sensation from the anterior tongue, and innervates lacrimal and salivary glands.

Cranial Nerve X (Vagus Nerve)

A mixed cranial nerve responsible for autonomic functions of the gut, sensation from the pharynx, and control of vocal cord muscles and swallowing.