Neurochemistry, Biological Rhythms, and Emotional Processing Flashcards

Comprehensive vocabulary flashcards covering neurochemistry, neurotransmitter pathways, neuropharmacology, sleep mechanisms, biological rhythms, emotions, and stress.

Exogenous Substance

A substance originating from an external source outside the body, such as a psychoactive drug.

Endogenous Substance

A substance produced internally within the body, such as a naturally occurring neurotransmitter.

Ionotropic Receptor

A fast-acting neurotransmitter receptor that forms a ligand-gated ion channel, changing shape to open or close the central channel when bound by a transmitter.

Metabotropic Receptor

A slow-acting, G-protein coupled neurotransmitter receptor that activates second messenger systems to open ion channels or alter intracellular chemical reactions.

Receptor Agonist

An endogenous or exogenous molecule that binds to a receptor, activates it, and initiates a functional response in the cell.

Receptor Antagonist

A substance that binds to a receptor without activating it, thereby blocking endogenous transmitters or agonist drugs from binding.

Ligand

Any chemical molecule or drug that binds specifically to a receptor protein.

Exocytosis

The cellular process triggered by an action potential's $Ca^{2+}$ influx that causes synaptic vesicles to fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft.

Criteria for a Neurotransmitter

A set of five rules requiring a substance to be synthesized/stored in presynaptic neurons, released upon action potential arrival, recognized by postsynaptic receptors, cause postsynaptic changes, and have its effects blocked when release is inhibited.

Amine Neurotransmitter

A structural class of small-molecule neurotransmitters based on single amino acid modifications, including acetylcholine, dopamine, serotonin, and norepinephrine.

Amino Acid Neurotransmitter

A class of neurotransmitters consisting of individual amino acid molecules, such as GABA, glutamate, glycine, and histamine.

Peptide Neurotransmitter

A neurotransmitter composed of short chains of 3 to 36 amino acids synthesized in the soma's Golgi apparatus, such as oxytocin, vasopressin, and endorphins.

Gas Neurotransmitter

A transmitter (e.g., nitric oxide, carbon monoxide) produced mainly in dendrites that diffuses freely without vesicles or membrane receptors and can act as a retrograde messenger.

Otto Loewi's Experiment

A classic experiment that stimulated the vagus nerve of a frog heart, collected surrounding fluid, and applied it to a second heart, proving chemical synaptic transmission by discovering Acetylcholine (ACh).

Acetylcholine (ACh)

The first discovered neurotransmitter, categorized as a quaternary amine, involved in cholinergic transmission in the basal forebrain, neuromuscular junctions, and autonomic nervous system.

Small-Molecule Neurotransmitters

A general size category of transmitters encompassing acetylcholine, biogenic amines, amino acids, and purines.

Biogenic Amines

A subgroup of small-molecule neurotransmitters containing nitrogen, comprising catecholamines, indoleamines, and imidazoleamines.

Catecholamines

A monoamine subfamily derived from tyrosine that includes dopamine, norepinephrine, and epinephrine.

Indoleamines

A monoamine subfamily that includes serotonin ($5\text{-}HT$) and melatonin.

Cholinergic Pathway

A neural projection system originating in nuclei of the basal forebrain that projects widely to the cortex, amygdala, and hippocampus, essential for learning and memory.

Mesostriatal Pathway

A dopaminergic pathway originating in the substantia nigra of the midbrain and projecting to the basal ganglia, playing a crucial role in motor control.

Mesolimbocortical Pathway

A dopaminergic pathway originating in the ventral tegmental area (VTA) and projecting to the nucleus accumbens, limbic system, and cortex, central to reward processing and reinforcement learning.

Raphe Nuclei

Midbrain and brainstem nuclei along the midline containing serotonergic neurons that project widely to the forebrain and spinal cord to modulate mood and behavior.

Locus Coeruleus

A noradrenergic nucleus in the brainstem projecting widely to the forebrain, involved in arousal, mood, sexual behavior, and sleep regulation.

Glutamate

The main excitatory amino acid neurotransmitter in the brain, interacting with receptors such as NMDA that are vital for memory formation.

Gamma-Aminobutyric Acid (GABA)

The primary inhibitory amino acid neurotransmitter in the central nervous system.

$GABA_A$ Receptor

An ionotropic receptor selective for $Cl^-$ ions that mediates fast inhibitory postsynaptic potentials and possesses binding sites for anxiolytic drugs like benzodiazepines.

Opioid Peptides

Endogenous neuropeptides (enkephalins, endorphins, dynorphins) that bind to opioid receptors to diminish pain perception.

Bioavailability

The proportion of an administered drug that enters systemic circulation and is free to act on its target tissue.

Biotransformation

The enzymatic conversion of drugs into active or inactive metabolites in organs like the liver, which can lead to side effects.

Blood-Brain Barrier (BBB)

Tight junction structural barriers between blood vessel endothelial cells in the CNS that limit the movement of large or hydrophilic drug molecules into brain tissue.

Ingestion Route

Drug administration via the gut (tablets, teas), characterized by slow-to-moderate absorption speeds influenced by digestive factors.

Inhalation Route

Drug administration via smoking or nasal snorting, utilizing rich vascularization in the lungs and nasal cavity for moderate-to-fast blood entry.

Peripheral Injection

Drug delivery through subcutaneous, intramuscular, intraperitoneal, or intravenous routes; intravenous delivery is rapid due to direct vascular entry.

Central Injection

Direct drug administration into the central nervous system (intracerebroventricular, intrathecal, epidural, intracerebral) to bypass the blood-brain barrier with fast to very fast effects.

Binding Affinity

The degree of chemical attraction between a ligand and a receptor; drugs with high affinity bind effectively even at low concentrations.

Efficacy

The intrinsic ability of a bound ligand to activate its receptor and elicit a cellular response.

Dose-Response Curve (DRC)

A graph plotting drug dose on a logarithmic scale against the magnitude of the observed biological response.

Effective Dose 50 ($ED_{50}$)

The dose at which a drug produces 50% of its maximum achievable response, or is effective in 50% of subjects.

Lethal Dose 50 ($LD_{50}$)

The dose at which a drug proves fatal to 50% of test animals.

Therapeutic Index

The safety margin between effective dose ($ED_{50}$) and lethal dose ($LD_{50}$); a wide index signifies higher drug safety.

Metabolic Tolerance

Drug tolerance resulting from organ systems (such as the liver) becoming increasingly efficient at metabolizing and eliminating a drug.

Functional Tolerance

Drug tolerance arising from altered tissue sensitivity, typically achieved by up-regulating or down-regulating receptor numbers in cell membranes.

Receptor Down-Regulation

A compensatory reduction in the total number of postsynaptic receptors triggered by chronic exposure to an agonist drug.

Receptor Up-Regulation

A compensatory increase in the number of postsynaptic receptors following long-term blockade by an antagonist drug.

Cross-Tolerance

The development of tolerance to an unexposed drug as a generalized consequence of repeated exposure to a chemically or functionally related drug.

Tetrodotoxin (TTX)

A neurotoxin found in puffer fish that selectively blocks voltage-gated $Na^+$ channels, preventing action potential propagation and causing paralysis.

Curare

A plant-derived toxin that acts as a competitive antagonist at nicotinic acetylcholine receptors on skeletal muscles, causing paralysis.

Botulinum Toxin (Botox)

A bacterial toxin that cleaves presynaptic vesicle release proteins, preventing ACh release at neuromuscular junctions to induce local paralysis.

Presynaptic Drug Mechanisms

Drug actions targeting the presynaptic neuron, categorized into effects on transmitter production, transmitter release, and transmitter clearance.

Antipsychotic (Neuroleptic) Drugs

First-generation medications for schizophrenia introduced in the 1950s that act as selective antagonists of dopamine $D_2$ receptors to relieve positive symptoms like delusions.

Atypical Neuroleptics

Second-generation schizophrenia drugs that block serotonin receptors in addition to dopamine receptors, helping treat refractory symptoms.

Monoamine Oxidase (MAO) Inhibitors

Antidepressants that block the enzymatic breakdown of monoamines in synaptic terminals, elevating transmitter availability in the cleft.

Tricyclic Antidepressants

Antidepressant drugs that increase synaptic neurotransmission by blocking the presynaptic reuptake of serotonin and norepinephrine.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressants (e.g., Prozac, Celexa) that bind directly to serotonin transporter proteins to inhibit 5-HT reuptake selectively.

Anxiolytics

A class of central nervous system depressant drugs specifically formulated to reduce anxiety and neuronal hyperexcitatory states.

Barbiturates

Early, highly addictive depressant anxiolytics and sleep aids that carry a high overdose risk due to a narrow therapeutic index.

Benzodiazepines

Anxiolytic drugs (e.g., Valium, Ativan) that bind to specific orphan sites on $GABA_A$ receptors to act as agonists, enhancing GABA-mediated chloride influx.

Morphine

The primary active analgesic opiate purified from opium that binds metabotropic opioid receptors in the periaqueductal gray to relieve pain.

Naloxone

A potent, competitive opioid receptor antagonist used as a rescue medication to rapidly reverse opiate overdose.

Nicotine

A tobacco alkaloid stimulant that activates nicotinic acetylcholine receptors in skeletal muscles, visceral organs, cortex, and VTA.

Biphasic Action of Alcohol

The characteristic dual effect of alcohol featuring an initial stimulant phase driven by dopamine pathways, followed by widespread neural depression.

Fetal Alcohol Syndrome (FAS)

A congenital disorder resulting from maternal alcohol abuse during pregnancy, producing facial dysmorphology, stunted growth, and central nervous system damage.

Korsakoff's Syndrome

A memory deficiency disorder caused by thiamine deficiency secondary to severe chronic alcoholism.

Delta-9-Tetrahydrocannabinol (THC)

The primary psychoactive compound in cannabis that acts on endogenous cannabinoid receptors ($CB_1$ and $CB_2$) in the brain.

Endocannabinoids

Endogenous lipid ligands, such as anandamide, that bind to cannabinoid GPCRs ($CB_1$ and $CB_2$) to modulate neural activity.

Caffeine

A stimulant drug that acts as a competitive antagonist at presynaptic adenosine receptors, blocking adenosine's normal inhibitory effects on transmitter release.

Cocaine

A potent stimulant derived from coca leaves that blocks reuptake transporters for monoamines, particularly dopamine, causing transmitter accumulation in synapses.

Amphetamine

A synthetic stimulant that triggers abnormally large catecholamine release from presynaptic terminals and blocks monoamine degradation.

Lysergic Acid Diethylamide (LSD)

A hallucinogenic drug that acts as a powerful agonist at serotonin $5\text{-}HT_{2A}$ receptors in the visual cortex.

MDMA (Ecstasy)

A hallucinogenic amphetamine derivative that stimulates monoamine release and oxytocin; long-term use damages cortical serotonin axons.

Dissociative Drugs

Compounds like PCP and Ketamine that block NMDA-type glutamate receptors, producing feelings of depersonalization and detachment from reality.

Substance Dependence

A severe substance disorder defined by compulsive drug self-administration, intense craving, significant time investment, and marked life disruption.

Moral Model of Drug Abuse

An explanatory framework attributing addiction to a personal lack of moral character and self-control.

Physical Dependence Model

A model stating that drug addiction is driven by a desire to avoid unpleasant physical and psychological withdrawal symptoms (dysphoria).

Positive Reward Model

A model asserting that drug self-administration is a learned behavior governed by positive reinforcement from brain reward circuitry.

Drug Self-Administration Paradigm

An experimental setup where animals press a lever to receive intravenous drug doses via a computerized syringe pump, measuring addictive potential.

Biological Rhythms

Regular, periodic fluctuations in any physiological or behavioral living process.

Circadian Rhythms

Endogenous biological rhythms that repeat approximately once every 24 hours.

Ultradian Rhythms

Biological rhythms that repeat more frequently than once a day, such as bouts of feeding, hormone surges, and activity bursts.

Infradian Rhythms

Biological rhythms that repeat less frequently than once a day, such as annual hibernation or reproductive cycles.

Diurnal

An organismic behavioral pattern characterized by being active during the light period and resting during the dark period.

Nocturnal

An organismic behavioral pattern characterized by being active during the dark period and resting during the light period.

Free-Running Animal

An animal expressing its endogenous circadian clock period in constant environmental conditions devoid of external time cues.

Phase Shift

A shift in the timing of a biological rhythm in response to a synchronizing environmental stimulus.

Entrainment

The process of synchronizing an endogenous biological clock to environmental light/dark cues.

Zeitgeber

An environmental cue used by an organism to entrain its circadian rhythm; translated from German as 'time-giver'.

Suprachiasmatic Nucleus (SCN)

A small nucleus in the hypothalamus located above the optic chiasm that contains the master endogenous circadian clock in mammals.

Retinohypothalamic Pathway

The neural tract conveying light information directly from specialized retinal ganglion cells in the eye to the SCN.

Melanopsin

A photopigment contained within specialized retinal ganglion cells that allows them to respond directly to light without rod or cone input.

Clock and Cycle

Two transcription factor proteins in SCN neurons that dimerize to promote the transcription of period (per) and cryptochrome (cry) genes.

Period (per) and Cryptochrome (cry)

Genes transcribed under Clock/Cycle control whose protein products bind together, enter the nucleus, and inhibit their own transcription in a 24-hour cycle.

Tau Mutation

A genetic mutation affecting circadian timing; hamsters with a tau mutation exhibit a free-running cycle significantly shorter than normal (~20 hours).

Melatonin

An amine hormone released by the pineal gland during the dark phase to signal nighttime duration to the brain.

Electroencephalogram (EEG)

A continuous scalp recording technique that measures summed electrical postsynaptic potentials from synchronously firing cortical pyramidal cells.

Beta Activity

Low-amplitude, high-frequency (>15–20 Hz) desynchronized EEG activity characteristic of an alert, awake mind.

Alpha Rhythm

A regular, synchronized EEG oscillation occurring at 8–12 Hz associated with a relaxed, resting awake state with eyes closed.

EEG Frequency Bands

Standard frequency band decompositions of EEG signals: Gamma (<25 Hz), Beta (12–25 Hz), Alpha (8–12 Hz), Theta (4–7 Hz), and Delta (1–4 Hz).

Slow-Wave Sleep (SWS)

Non-REM sleep divided into three stages, characterized by slow, high-amplitude EEG activity and reduced muscle tone.

Rapid-Eye-Movement (REM) Sleep

A sleep stage characterized by low-amplitude, high-frequency EEG activity, rapid eye movements, vivid dreaming, and postural muscle atonia.