Key Concepts in Neurotransmission and Cardiovascular Pharmacology

Acetylcholine

A neurotransmitter used by both the parasympathetic and sympathetic nervous systems. It plays a role in transmitting signals in autonomic ganglia and at parasympathetic target organs.

Acetylcholinesterase

An enzyme that breaks down acetylcholine in the synaptic cleft, terminating its action.

Adrenal glands

Endocrine glands located on top of each kidney that secrete adrenaline and noradrenaline in response to sympathetic stimulation.

Adrenal medulla

The inner part of the adrenal glands that releases adrenaline and noradrenaline directly into the bloodstream during stress.

Adrenaline

A hormone and neurotransmitter released by the adrenal medulla and some sympathetic nerves, involved in the 'fight or flight' response. Also known as epinephrine.

Afferent

Refers to sensory neurons that carry information from the body to the central nervous system.

Autonomic nervous system

A branch of the peripheral nervous system that regulates involuntary processes such as heart rate, digestion, and glandular secretion. It includes the sympathetic, parasympathetic, and enteric divisions.

Axon

A long projection of a neuron that transmits electrical signals from the cell body to target cells or tissues.

Catechol

A chemical structure consisting of a benzene ring with two adjacent hydroxyl groups, forming the backbone of catecholamines.

Catecholamine

A group of neurotransmitters and hormones, including dopamine, noradrenaline, and adrenaline, derived from tyrosine and containing a catechol group.

Catechol-O-methyltransferase (C⁠O⁠M⁠T)

An enzyme that metabolises catecholamines by adding a methyl group, reducing their activity.

Central nervous system (CNS)

The brain and spinal cord, responsible for processing and integrating sensory information and coordinating motor output.

Choline acetyltransferase

An enzyme that synthesizes acetylcholine from choline and acetyl-CoA.

Dopa decarboxylase

An enzyme that converts L-DOPA into dopamine in catecholamine biosynthesis.

Dopamine

A catecholamine neurotransmitter involved in motor control, reward, and mood regulation.

Dopamine beta hydroxylase

An enzyme that converts dopamine into noradrenaline.

Epinephrine

The US term for adrenaline.

Enteric nervous system

A division of the autonomic nervous system located in the gastrointestinal tract, capable of regulating digestion independently of the CNS.

Fast synaptic transmission

Rapid communication between neurons or neurons and target cells, typically mediated by neurotransmitters like acetylcholine or glutamate.

Ganglion (plural ganglia)

A cluster of nerve cell bodies in the peripheral nervous system where synapses occur between pre-ganglionic and post-ganglionic neurons.

G protein

A membrane associated protein that links G protein coupled receptors to intracellular signalling pathways.

G protein coupled receptor

A type of receptor that transduces extracellular signals into cellular responses via G-proteins.

L-DOPA

A precursor to dopamine used in dopamine synthesis. Used in the treatment of Parkinson's disease.

Monoamine

A class of neurotransmitters that includes catecholamines (dopamine, noradrenaline, adrenaline), serotonin, histamine and melatonin.

Monoamine oxidase (M⁠A⁠O)

An enzyme that degrades monoamines such as dopamine, noradrenaline, and adrenaline, reducing their activity.

Motor

Refers to neurons or pathways that carry commands from the CNS to muscles or glands, enabling movement or secretion.

Muscarinic acetylcholine receptor

A type of acetylcholine receptor found on parasympathetic target tissues, responsible for slower, modulatory responses.

N⁠E⁠T

The noradrenaline transporter, which removes noradrenaline from the synaptic cleft to terminate its action.

Nicotinic acetylcholine receptors

Ion channel receptors activated by acetylcholine, found at autonomic ganglia and on skeletal muscle at neuromuscular junctions.

Noradrenaline

A neurotransmitter and hormone released by sympathetic nerves and the adrenal medulla, involved in the 'fight or flight' response.

Norepinephrine

The US term for noradrenaline.

Paravertebral ganglia

Sympathetic ganglia arranged in chains on either side of the vertebral column.

Parasympathetic nervous system

A branch of the autonomic nervous system responsible for 'rest and digest' functions, promoting relaxation and conservation of energy.

Peripheral nervous system

All nerves outside the central nervous system, including the somatic and autonomic nervous systems.

Phenylethanolamine-N-methyltransferase

An enzyme that converts noradrenaline into adrenaline in the adrenal medulla.

Post-ganglionic neuron

A neuron in the autonomic nervous system that transmits signals from a ganglion to the target tissue.

Pre-ganglionic neuron

A neuron in the autonomic nervous system that transmits signals from the CNS to an autonomic ganglion.

Prevertebral ganglia

Sympathetic ganglia located near major abdominal arteries, innervating abdominal and pelvic organs.

Somatic nervous system

The part of the peripheral nervous system that controls voluntary movements of skeletal muscles.

Sympathetic nervous system

A branch of the autonomic nervous system responsible for 'fight, fright or flight' responses, increasing heart rate, blood pressure, and energy mobilization.

Tyrosine hydroxylase

An enzyme that catalyzes the conversion of tyrosine to L-DOPA, the first step in catecholamine synthesis.

Uptake 2

A low-affinity transport mechanism for removing catecholamines from the extracellular space, primarily in non-neuronal tissues.

Adenylyl cyclase

An enzyme that converts ATP to cyclic AMP (cAMP), a second messenger involved in signalling pathways.

Agonist

A ligand that binds to a receptor and activates it. Usually it will bind to the same site as the neurotransmitter or hormone that the receptor recognises.

Antagonist

A ligand that binds to a receptor and stops it from activating. This may be because it blocks the agonist binding site, or it may act at a different site.

cAMP

Cyclic adenosine monophosphate. An important intracellular second messenger.

DAG

Diacylglycerol, a second messenger that along with calcium, activates protein kinase C.

Enzyme-linked receptor

A type of receptor that has intrinsic enzymatic activity or is associated with an enzyme and transduces signals via catalysis.

Ionotropic glutamate receptors

A superfamily of ligand gated ion channels that mediate fast synaptic transmission in the central nervous system by binding glutamate.

IP3

Inositol 1,4,5-trisphosphate, a second messenger that mobilizes calcium from intracellular stores.

IP3 receptor

An intracellular receptor that binds IP3 and mediates the release of calcium from the endoplasmic or sarcoplasmic reticulum.

Kinase

An enzyme that transfers phosphate groups from high-energy molecules, such as ATP, to specific substrates, a process called phosphorylation.

Ligand

Any molecule that binds to a receptor.

Ligand gated ion channel

A type of receptor that opens an ion channel in response to the binding of a specific chemical ligand.

Nuclear receptor

A type of receptor located within the cell nucleus or cytoplasm that binds to hormones and other ligands to regulate gene expression.

Orphan receptor

A receptor whose natural ligand is unknown.

Pentameric ligand gated channel

A superfamily of ligand gated ion channels composed of five subunits arranged symmetrically around a central pore.

Phosphodiesterase

An enzyme that breaks down cyclic nucleotides like cAMP and cGMP, regulating signal transduction pathways.

Phospholipase C

An enzyme that cleaves phospholipids to generate second messengers such as IP3 and DAG.

PIP2

Phosphatidylinositol 4,5-bisphosphate, a membrane phospholipid that is a precursor for second messengers like IP3 and DAG.

Protein kinase A

A serine/threonine kinase activated by cyclic AMP (cAMP) that regulates various cellular processes.

Protein kinase C

A family of serine/threonine kinases activated by DAG and calcium, involved in regulating various cellular processes.

Receptor

A protein molecule that receives chemical signals from outside a cell and initiates a cellular response.

Receptor tyrosine kinases

A superfamily of enzyme-linked receptors that phosphorylate tyrosine residues on target proteins to propagate signals.

Ryanodine receptor

An intracellular calcium channel that releases calcium from the sarcoplasmic or endoplasmic reticulum in response to signals.

Second messenger

A small intracellular molecule that transmits signals from receptors to target molecules within the cell.

Signal transduction

The process by which a signal from a receptor is converted into a cellular response, often involving a series of molecular events.

Superfamily

A large group of related proteins that share structural and functional characteristics.

Subunit

A component protein of a receptor (and other types of protein). Receptors are frequently made up of a number of subunits that are held together by (usually) non-covalent bonds. The arrangement of subunits in the protein complex defines its quaternary structure.

monomer (monomeric)

A single subunit.

dimer (dimeric)

A structure that contains two subunits.

trimer (trimeric)

A structure that contains three subunits.

tetramer (tetrameric)

A structure that contains four subunits.

pentamer (pentameric)

A structure that contains five subunits.

hexamer (hexameric)

A structure that contains six subunits.

α2δ (alpha 2 delta) subunit

An accessory subunit of voltage-gated calcium channels that helps modulate their function and trafficking.

Accessory subunit

A protein subunit that associates with a primary channel subunit to modulate its properties or localization.

Activation gate

The part of an ion channel that opens to allow ion flow in response to a stimulus.

Active transport

The movement of ions or molecules across a membrane against their concentration gradient, requiring energy input, often from ATP.

Alpha (α) subunit (voltage gated channel)

The main subunit of a voltage-gated ion channel, forming the pore and responsible for the channel's primary functions.

Carrier protein

A membrane protein that facilitates the transport of specific substances across the cell membrane by binding and releasing them.

CaV

Short for voltage-gated calcium channel.

Chemical gradient

A difference in the concentration of a specific substance across a membrane.

Closed state

A state of an ion channel in which the channel is not conducting ions, even though it may be ready to open.

Conductance

A measure of how easily ions flow through an ion channel, influenced by the channel's properties and ion concentration.

Cryo-electron microscopy

A technique used to visualize molecular structures at high resolution by freezing samples and imaging them with electrons.

Current

The flow of electric charge, in this context, caused by the movement of ions through ion channels.

Dendrogram

A tree-like diagram that shows the relationships between different proteins, often used to compare ion channel families.

Electrical gradient

A difference in electric charge across a membrane, which influences the movement of ions.

Electrochemical gradient

The combined effect of the chemical gradient and electrical gradient that drives the movement of ions.

Electrophysiology

The study of electrical properties of biological cells and tissues, often involving the measurement of ion channel activity.

Gating

The process by which ion channels open or close in response to stimuli such as voltage, ligands, or mechanical forces.

Hydration shell

A layer of water molecules surrounding an ion, affecting its size and interaction with ion channels.

Inactivated state

A state of an ion channel in which it cannot conduct ions, typically occurring after opening.

Inactivation gate

A structure within an ion channel that blocks the pore to stop ion flow during the inactivated state.

Ion channel

A protein that forms a pore in the cell membrane, allowing specific ions to pass through down their electrochemical gradient.

Ion pump

A membrane protein that uses energy to actively transport ions across a membrane against their gradient.

Knock on

A mechanism of ion permeation where an incoming ion displaces another ion already in the channel.

KV

Short for potassium voltage-gated channels.

L type calcium channels

A type of voltage-gated calcium channel involved in long-lasting calcium currents, important in muscle contraction and neurotransmission.