Neurotransmitters and Receptors

Vocabulary practice flashcards covering neurotransmitters, neuromodulators, receptor types, pathways, and synaptic transmission principles.

Neurotransmitters

Chemical messengers that function in rapid communication (within a few milliseconds) by acting on a postsynaptic cell to produce an excitatory postsynaptic potential (EPSP) or an inhibitory postsynaptic potential (IPSP).

Neuromodulators

Chemical messengers that modify and regulate synaptic transmission activities, eliciting complex responses slower than simple EPSPs or IPSPs by acting presynaptically or altering DNA/protein synthesis over minutes, hours, or days.

Choline Acetyltransferase (ChAT)

The enzyme responsible for synthesizing acetylcholine (ACh) from choline and acetyl coenzyme A (acetyl-CoA).

Acetylcholinesterase (AChE)

The enzyme located on the postsynaptic membrane that rapidly breaks down acetylcholine (ACh) in the synaptic cleft into choline and acetate.

Nicotinic Receptors

Ionotropic ligand-gated ion channels for acetylcholine located at skeletal muscle motor end plates and CNS neurons; producing fast, short-lived responses, blocked by curare at motor end plates and hexamethonium at autonomic ganglia.

Muscarinic Receptors

Metabotropic G-protein coupled acetylcholine receptors (subclasses $M_1$ through $M_5$) expressed at autonomic neuroeffector junctions, producing slower and longer-lived responses that are blocked by atropine.

Myasthenia Gravis

An autoimmune disorder with an incidence of $3$ in $10{,}000$ characterized by antibody attack on nicotinic acetylcholine receptors leading to muscle weakness, treated using acetylcholinesterase inhibitors.

Biogenic Amines

A class of neurotransmitters synthesized from amino acids that contain an amino ($\text{NH}_2$) group, including catecholamines (from tyrosine), serotonin (from tryptophan), and histamine (from histidine).

Catecholamines

A subcategory of biogenic amines synthesized sequentially from the amino acid tyrosine, consisting of dopamine, norepinephrine, and epinephrine.

Tyrosine Hydroxylase

The rate-limiting enzyme that converts tyrosine into L-Dopa during the biosynthetic pathway of catecholamines.

Dopamine

A catecholamine neurotransmitter active in brain pathways for reward, attention, and addiction; its reuptake is blocked by cocaine and methamphetamine, and loss of dopaminergic neurons in the substantia nigra leads to Parkinson's disease.

Norepinephrine

A major catecholamine neurotransmitter released by sympathetic postganglionic neurons that acts on adrenergic $\alpha_1$, $\alpha_2$, and $\beta_1$ receptors.

Epinephrine

A catecholamine hormone secreted by the adrenal medulla that binds to all adrenergic receptor subtypes ($\alpha_1$, $\alpha_2$, $\beta_1$, $\beta_2$, $\beta_3$).

Serotonin (5-HT)

A biogenic amine neurotransmitter synthesized from tryptophan that plays key roles in mood, sleep/wakefulness, and sensory/motor pathways; degraded by monoamine oxidase (MAO) and targeted by psychotropic medications.

Glutamate

The primary excitatory neurotransmitter in the central nervous system, binding to ionotropic receptors such as AMPA and NMDA.

NMDA Receptor

An ionotropic glutamate receptor permeable to $\text{Ca}^{2+}$ that is blocked by $\text{Mg}^{2+}$ at resting potential; postsynaptic depolarization expels $\text{Mg}^{2+}$, allowing $\text{Ca}^{2+}$ influx essential for long-term potentiation.

Excitotoxicity

Neuronal injury or death caused by excessive $\text{Ca}^{2+}$ entry during overactivation of NMDA glutamate receptors, associated with conditions like stroke, epilepsy, and brain trauma.

Long-Term Potentiation (LTP)

A persistent strengthening of synaptic transmission triggered by high-frequency action potentials, mediated by cooperative action of AMPA and NMDA receptors to increase postsynaptic sensitivity and presynaptic glutamate release.

Gamma-Aminobutyric Acid (GABA)

The primary inhibitory neurotransmitter in the brain, synthesized from glutamate, acting through $\text{GABA}_A$ and $\text{GABA}_B$ receptors.

GABA_A Receptor

A ligand-gated ion channel receptor that opens chloride ($\text{Cl}^-$) channels to hyperpolarize the membrane potential, serving as the target for anti-anxiety and sleep medications like benzodiazepines and barbiturates.

Glycine

An inhibitory amino acid neurotransmitter operating mainly in the spinal cord and brain stem by opening chloride channels to hyperpolarize postsynaptic cells, competitively blocked by strychnine.

Neuropeptides

Peptidergic messengers composed of two or more amino acids synthesized as inactive precursors in the cell body, moved to terminals by axonal transport, and cleaved to yield active peptides mediating slow EPSPs or IPSPs.

Opioid Peptides

Endogenous peptidergic transmitters (enkephalins, dynorphins, and beta-endorphins) involved in pain and anxiety suppression that act on kappa, delta, and mu receptors; agonized by morphine and antagonized by naloxone.

Nitric Oxide (NO)

A freely diffusible gaseous neuromodulator synthesized from arginine and $\text{O}_2$ via nitric oxide synthase (NOS), yielding citrulline as a byproduct and acting as a retrograde messenger in long-term potentiation.

Purinergic Receptors

Receptors classified into $P1$ receptors (responding to adenosine, with subtypes $A_1, A_{2A}, A_{2B}, A_3$) and $P2$ receptors (responding to ATP, divided into metabotropic $P2Y, P2U, P2T$ and ionotropic $P2X, P2Z$).