Neural Signals & Neuropharmacology

Flashcards covering key vocabulary related to neural signals, neuron doctrine, action potentials, synaptic transmission, neurotransmitters, receptors, and the chemistry of behavior including drug actions and classes.

The Neuron Doctrine

States that the elementary functional unit of the brain is the neuron, and neurons are discrete, communicating via synapses.

Neurons

Basic units of the nervous system responsible for transmitting information within the nervous system and capable of generating action potentials.

Glial cells

Cells in the nervous system that act to support neurons.

Potential

The capacity to do work, created by electrostatic charges.

Resting Membrane Potential (RMP)

The electrical potential difference across the cell membrane when the cell is at rest, typically -50 to -80mV (for a neuron, usually -65 mV), with the inside of the cell being more negative than the outside.

Extracellular fluid

Fluid surrounding cells, containing water and electrically charged ions like Sodium+ and Potassium K+, distributed in a specific way.

Sodium (Na+)

An ion that is more concentrated outside the neuron at rest.

Potassium (K+)

An ion that is more concentrated inside the neuron at rest.

Neuronal Membrane (Phospholipid membrane)

A phospholipid bilayer that acts as a barrier between the cytosol and extracellular fluid, preventing free passage of ions.

Ion channels

Membrane proteins that allow specific ions to cross a cell membrane through an appropriately shaped pore.

Gated channels

Membrane proteins that change shape to allow or prevent the passage of substances depending on whether their gates are open or closed.

Pump (transporter)

A membrane protein that changes shape to carry substances across a cell membrane, requiring energy (ATP) and sometimes moving multiple ions simultaneously.

Selective permeability

A property of a membrane that allows some substances to flow through while restricting others (e.g., neurons allow K+ to pass freely but not Na+).

Diffusion

The movement of ions down their concentration gradient, causing them to spread from areas of high concentration to low concentration to reach equilibrium.

Electrostatic pressure

The force that causes charged ions to flow towards oppositely charged areas and repel similarly charged areas.

Sodium-potassium pump

An active transport mechanism that maintains the resting membrane potential by pumping 3 Na+ ions out of the cell for every 2 K+ ions pumped into the cell, consuming energy.

Hyperpolarization

An increase in membrane potential, where the interior of the cell becomes even more negative and farther from zero (below resting state).

Depolarization

A decrease in membrane potential, where the interior of the cell becomes less negative and closer to zero. (getting closer to threshold).

Local potentials (Graded potentials)

Small, temporary, localized fluctuations in the resting membrane potential, with variable amplitude depending on stimulus strength, that diminish over time.

Threshold potential

The critical level of depolarization (approximately -40mV) that must be reached for an action potential to be triggered.

Action Potential (AP)

A rapid, all-or-none change in the membrane potential in response to a threshold stimulus, followed by a return to resting membrane potential, propagating from the axon hillock to the axon terminal.

All-or-none property

A characteristic of action potentials, meaning a neuron either fires completely or not at all, and the amplitude of the action potential is independent of the stimulus size.

Depolarization phase (AP)

The rising phase of an action potential where voltage-gated Na+ channels open, allowing Na+ to rush into the cell, making the membrane potential rapidly positive.

Repolarization phase (AP)

The falling phase of an action potential where voltage-gated Na+ channels inactivate and voltage-gated K+ channels open, allowing K+ to rush out of the cell, returning the membrane potential to negative values.

Hyperpolarization (undershoot) (AP)

A transient period after repolarization where the membrane potential becomes more negative than the resting membrane potential due to the continued efflux of K+ ions before all gated channels close.

Absolute refractory phase

A period during which no action potential can be produced, regardless of the strength of the stimulus, because voltage-gated Na+ channels are inactivated.

Relative refractory phase

A period during which an action potential can be triggered, but only by a stronger-than-normal stimulus, as the membrane is hyperpolarized and more K+ channels are still open.

Saltatory conduction

The propagation of an action potential along myelinated axons, where the electrical signal 'jumps' from one node of Ranvier to the next, speeding up transmission.

Postsynaptic Potentials

Brief changes in the membrane potential of the postsynaptic cell in response to the binding of a neurotransmitter, lasting approximately 10-100ms.

Excitatory Postsynaptic Potential (EPSP)

A depolarization of the postsynaptic membrane, typically caused by the opening of Na+ channels, making the cell less negative and increasing the likelihood of an action potential.

Inhibitory Postsynaptic Potential (IPSP)

A hyperpolarization of the postsynaptic membrane, typically caused by the opening of Cl- channels, making the cell more negative and decreasing the likelihood of an action potential.

Spatial summation

The integration of simultaneous postsynaptic potentials (EPSPs or IPSPs) originating from different synapses on the same postsynaptic neuron, which combine at the axon hillock to influence firing.

Temporal summation

The integration of postsynaptic potentials (EPSPs or IPSPs) that arrive at a single synapse in rapid succession, adding together over time to influence the postsynaptic neuron's firing.

Axon hillock

The 'integration zone' of the neuron, located at the junction of the cell body and axon, where postsynaptic potentials are summed, and if threshold is reached, an action potential is initiated.

Presynaptic cell

The neuron that releases neurotransmitters into the synaptic cleft.

Postsynaptic cell

The neuron that receives neurotransmitters at the synapse.

Synaptic cleft

The narrow gap or space between the presynaptic and postsynaptic neurons at a synapse.

Synaptic vesicle

Small, membrane-bound sacs within the presynaptic terminal that contain and store neurotransmitters, releasing them into the synaptic cleft upon stimulation.

Neurotransmitters (NTs)

Chemical messengers synthesized in presynaptic neurons, stored in axon terminals, released when action potentials arrive, and recognized by receptors on the postsynaptic membrane to cause changes.

Voltage-gated Ca2+ channels

Channels in the presynaptic terminal that open in response to an action potential, allowing calcium influx, which triggers the fusion of synaptic vesicles and neurotransmitter release.

Reuptake transporter

A membrane protein on the presynaptic terminal that actively reabsorbs neurotransmitters from the synaptic cleft back into the presynaptic neuron, thereby terminating their action.

Autoreceptor

A receptor located on the presynaptic neuron that responds to the neurotransmitter released by that same neuron, often providing feedback to regulate further neurotransmitter synthesis or release.

Ligand

Any substance (e.g., a neurotransmitter or drug) that binds to a receptor molecule.

Agonist

A substance that binds to a receptor and mimics or enhances the actions of an endogenous neurotransmitter.

Antagonist

A substance that binds to a receptor and blocks or impedes the actions of an endogenous neurotransmitter.

Amino acid neurotransmitters

A major class of neurotransmitters, including GABA and glutamate.

Glutamate

The most widespread excitatory neurotransmitter in the brain, with major receptors like AMPA and NMDA.

GABA

The most widespread inhibitory neurotransmitter in the brain, with GABAa receptors allowing Cl- ions into the postsynaptic cell.

Amine neurotransmitters

A major class of neurotransmitters, including acetylcholine, dopamine, serotonin, and norepinephrine.

Acetylcholine (ACh)

An amine neurotransmitter playing a major role in transmission in the forebrain; its widespread loss is associated with Alzheimer's disease.

Nicotinic receptors

A subtype of acetylcholine receptor crucial for muscle contraction.

Muscarinic receptors

A subtype of acetylcholine receptor important in parasympathetic function.

Dopamine (DA)

An amine neurotransmitter with major roles in motor control, learning, and positive reinforcement.

Mesolimbocortical pathway

A major dopamine pathway projecting from the ventral tegmental area (VTA) to the nucleus accumbens and cortex, associated with reward and motivation.

Mesostriatal pathway

A major dopamine pathway projecting from the substantia nigra to the basal ganglia, crucial for motor control; its degeneration is linked to Parkinson's disease.

MPTP

A neurotoxin that is metabolized to MPP+, which is toxic to dopamine neurons in the substantia nigra and is used as a model for Parkinson's disease.

Norepinephrine (noradrenaline)

An amine neurotransmitter important in controlling many behaviors, including alertness, mood, and sexual behavior.

Serotonin (5-HT)

An amine neurotransmitter that participates in the control of various behaviors, including mood, vision, anxiety, sexual behavior, and sleep, with many different receptor subtypes.

Peptide neurotransmitters (Neuropeptides)

A class of neurotransmitters including opioid peptides (e.g., endorphins) and peptide hormones (e.g., oxytocin, vasopressin).

Opioid peptides

Neuropeptides, such as endorphins, that reduce the perception of pain and are mimicked by opiate drugs like morphine.

Oxytocin and Vasopressin

Peptide hormones that contribute to memory and pair-bonding.

Gas neurotransmitters

A class of non-conventional neurotransmitters, like nitric oxide, that are produced outside axon terminals, diffuse out instantly, do not use receptors, diffuse into target cells, activate second messengers, and can function as retrograde transmitters.

Ionotropic receptor

A neurotransmitter receptor that contains an ion channel (pore) which opens directly in response to neurotransmitter binding, resulting in fast and brief effects.

Metabotropic receptor

A neurotransmitter receptor that does not contain an ion channel but activates a G protein in response to neurotransmitter binding, leading to slower, longer-lasting, and more complex effects via signal transduction cascades.

NMDA Receptor

An ionotropic, ligand-gated ion channel for glutamate, responsible for fast, direct excitation and rapid synaptic transmission.

MGLUR (Metabotropic Glutamate Receptor)

A metabotropic (GPCR) glutamate receptor that, upon activation, initiates a signal transduction cascade, causing slower, prolonged modulation of neural activity.

Binding affinity

The degree of chemical attraction or strength of binding between a ligand (e.g., a drug or neurotransmitter) and its receptor.

Efficacy

The ability of a bound ligand to activate its receptor and produce a biological response.

Enteral administration

Routes of drug administration involving the gastrointestinal tract, such as oral, rectal, and sublingual.

Parenteral administration

Routes of drug administration that bypass the gastrointestinal tract, such as intramuscular, subcutaneous, intravenous, and intradermal injections.

Topical administration

Routes of drug administration applied to body surfaces, such as epidermic, instillation, and irrigation.

Inhalation administration

Routes of drug administration where substances are breathed in, such as vaporization, gas inhalation, and nebulization.

Drug tolerance

A reduced response to a drug after repeated exposure, requiring higher doses to achieve the same effect.

Metabolic tolerance

A type of drug tolerance resulting from the body's increased ability to metabolize or break down a drug (e.g., enzymatic upregulation).

Functional tolerance

A type of drug tolerance resulting from changes in the sensitivity or number of drug receptors (e.g., receptor up or down regulation).

Cross-tolerance

A phenomenon where tolerance to one drug generalizes to other drugs in the same class or with similar mechanisms of action.

Stimulants

A class of drugs that increase central nervous system activity, leading to desired effects like elation and increased alertness, but also side effects like increased heart rate and irritability.

Depressants

A class of drugs that reduce central nervous system activity, often leading to relaxation and anxiety reduction, but also lethargy and impaired coordination (e.g., alcohol).

Analgesics

A class of drugs primarily used for pain relief (e.g., opioids).

Hallucinogens (Psychedelics)

A class of drugs that cause profound perceptual changes, altered perceptions, and sometimes insightful experiences.

Psychotherapeutic drugs

A broad class of drugs used to treat mental disorders, including antipsychotics, antidepressants, and anxiolytics.

Mesolimbocortical DA pathway

A key dopamine pathway, central to the reward system, that is activated by virtually all drugs of abuse, causing dopamine release in the nucleus accumbens (NAcc).

Cocaine

A high-efficacy stimulant derived from the coca shrub that blocks the reuptake of dopamine, leading to its accumulation in the synapse.

Amphetamine ('speed')

A stimulant more potent than cocaine, which both stimulates a larger-than-normal release of dopamine and blocks its reuptake and metabolic breakdown.

Alcohol

A drug with biphasic effects (initially stimulant, then prolonged depressant) that inhibits neural excitability by acting on GABAa receptors and antagonizing glutamate receptors, also affecting the dopamine system.

Synesthesia

A merging of senses, often experienced during a psychedelic trip, where stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway.

Ego death / transcendence

A profound experience during a psychedelic trip characterized by a temporary loss of one's sense of self and a feeling of merging with something larger.

5-HT2A receptors

Serotonin receptors, densely distributed in the visual cortex, that are targeted by many serotonergic psychedelic drugs like LSD and psilocybin.

MDMA (Ecstasy)

A psychoactive drug that stimulates 5-HT receptors in the visual cortex and affects dopamine and oxytocin, often causing prosocial feelings like empathy and well-being.

Cannabis

A drug with mixed stimulant and hallucinogenic properties, derived from the cannabis sativa plant, with the active ingredient delta-9-tetrahydrocannabinol (THC).

Delta-9-tetrahydrocannabinol (THC)

The primary active ingredient in cannabis, responsible for its psychoactive effects.

Cannabinoid Receptor 1 (CB1)

A cannabinoid receptor found primarily in the brain (especially the substantia nigra, hippocampus, and cortex), for which anandamide (AEA) is an endogenous ligand.

Cannabinoid Receptor 2 (CB2)

A cannabinoid receptor found primarily in the immune system.

Anandamide (AEA)

An endogenous ligand (endocannabinoid) for CB1 receptors.

Retrograde signaling

A mechanism of endocannabinoid action where the postsynaptic cell releases endocannabinoids that act on presynaptic CB1 receptors, inhibiting neurotransmitter release from the presynaptic cell.

Opioids

A class of drugs including opium, morphine, heroin, and fentanyl, that provide pain relief, relaxation, and euphoria by acting as agonists for opioid receptors, ultimately increasing dopamine in the nucleus accumbens.

Periaqueductal gray (PAG)

A brain region where opioids bind to opioid receptors to regulate pain perception.

Heroin

A high-efficacy opioid that acts as an agonist for opioid receptors, affecting the endorphin system and indirectly increasing dopamine in the nucleus accumbens.