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SA node cell to atrial cardiac muscle cell signaling

Definition

Target type: biologicalprocess

Any process that mediates the transfer of information from an SA node cardiomyocyte to an atrial cardiomyocyte. [GOC:BHF, GOC:mtg_cardiac_conduct_nov11]

The Sinoatrial (SA) node, located in the right atrium, is the heart's natural pacemaker. It generates electrical impulses that trigger heartbeats, initiating the cardiac cycle. These impulses are transmitted to the atrial cardiac muscle cells, causing their contraction and subsequently pumping blood to the ventricles.

The signaling process between the SA node and atrial muscle cells involves a coordinated sequence of events:

1. **SA Node Action Potential Generation:** The SA node cells are specialized pacemaker cells that exhibit spontaneous depolarization due to a unique combination of ion channels. These channels allow for inward movement of sodium (Na+) and calcium (Ca2+) ions, gradually increasing the cell's membrane potential until it reaches the threshold for action potential generation.

2. **Action Potential Conduction:** The action potential generated by the SA node cells spreads rapidly through the atrial muscle cells via specialized gap junctions, which allow the passage of ions and electrical signals between cells. These gap junctions ensure synchronized contraction of the atria.

3. **Atrial Muscle Cell Excitation:** As the action potential reaches the atrial muscle cells, it causes a rapid influx of Ca2+ ions through voltage-gated calcium channels. This calcium influx triggers a cascade of events that ultimately lead to muscle contraction:
- **Calcium-Induced Calcium Release:** The influx of Ca2+ into the sarcoplasm (the cytoplasm of muscle cells) triggers the release of even more Ca2+ from the sarcoplasmic reticulum, an intracellular organelle that stores calcium.
- **Cross-Bridge Formation:** The increased intracellular calcium concentration enables the binding of calcium to troponin, a protein that regulates the interaction of actin and myosin filaments, the contractile proteins of muscle cells.
- **Muscle Contraction:** This binding allows the myosin heads to attach to actin filaments, forming cross-bridges. The interaction between actin and myosin results in muscle contraction.

4. **Repolarization and Relaxation:** Once the SA node action potential has passed, the atrial muscle cells repolarize. This involves the efflux of potassium (K+) ions, restoring the resting membrane potential. The reduction of calcium in the sarcoplasm leads to the detachment of myosin heads from actin filaments, allowing the muscles to relax and prepare for the next contraction cycle.

This intricate signaling process ensures the efficient and coordinated contraction of the atria, which is essential for propelling blood to the ventricles and maintaining the rhythm of the heart.'
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Proteins (1)

ProteinDefinitionTaxonomy
Voltage-dependent T-type calcium channel subunit alpha-1GA voltage-dependent T-type calcium channel subunit alpha-1G that is encoded in the genome of human. [PRO:WCB, UniProtKB:O43497]Homo sapiens (human)

Compounds (12)

CompoundDefinitionClassesRoles
tacrinetacrine : A member of the class of acridines that is 1,2,3,4-tetrahydroacridine substituted by an amino group at position 9. It is used in the treatment of Alzheimer's disease.

Tacrine: A cholinesterase inhibitor that crosses the blood-brain barrier. Tacrine has been used to counter the effects of muscle relaxants, as a respiratory stimulant, and in the treatment of Alzheimer's disease and other central nervous system disorders.
acridines;
aromatic amine
EC 3.1.1.7 (acetylcholinesterase) inhibitor
nimodipinenimodipine : A dihydropyridine that is 1,4-dihydropyridine which is substituted by methyl groups at positions 2 and 6, a (2-methoxyethoxy)carbonyl group at position 3, a m-nitrophenyl group at position 4, and an isopropoxycarbonyl group at position 5. An L-type calcium channel blocker, it acts particularly on cerebral circulation, and is used both orally and intravenously for the prevention and treatment of subarachnoid hemorrhage from ruptured intracranial aneurysm.

Nimodipine: A calcium channel blockader with preferential cerebrovascular activity. It has marked cerebrovascular dilating effects and lowers blood pressure.
2-methoxyethyl ester;
C-nitro compound;
dicarboxylic acids and O-substituted derivatives;
diester;
dihydropyridine;
isopropyl ester
antihypertensive agent;
calcium channel blocker;
cardiovascular drug;
vasodilator agent
pimozidepimozide : A member of the class of benzimidazoles that is 1,3-dihydro-2H-benzimidazol-2-one in which one of the nitrogens is substituted by a piperidin-4-yl group, which in turn is substituted on the nitrogen by a 4,4-bis(p-fluorophenyl)butyl group.

Pimozide: A diphenylbutylpiperidine that is effective as an antipsychotic agent and as an alternative to HALOPERIDOL for the suppression of vocal and motor tics in patients with Tourette syndrome. Although the precise mechanism of action is unknown, blockade of postsynaptic dopamine receptors has been postulated. (From AMA Drug Evaluations Annual, 1994, p403)
benzimidazoles;
heteroarylpiperidine;
organofluorine compound
antidyskinesia agent;
dopaminergic antagonist;
first generation antipsychotic;
H1-receptor antagonist;
serotonergic antagonist
mibefradilMibefradil: A benzimidazoyl-substituted tetraline that selectively binds and inhibits CALCIUM CHANNELS, T-TYPE.tetralinsT-type calcium channel blocker
vexibinolsophoraflavanone G : A tetrahydroxyflavanone having a structure of naringenin bearing an additional hydroxyl substituent at position 2' as well as a (2R)-5-methyl-2-(prop-1-en-2-yl)hex-4-en-1-yl (lavandulyl) substituent at position 8'.

vexibinol: flavanol from Sophora; structure in first source; RN given refers to (S-(R*,S*))-isomer
(2S)-flavan-4-one;
4'-hydroxyflavanones;
tetrahydroxyflavanone
antimalarial;
antimicrobial agent;
antioxidant;
plant metabolite
8-prenylnaringenin8-prenylnaringenin: a phytogenic antineoplastic agent; structure in first source

sophoraflavanone B : A trihydroxyflavanone that is (S)-naringenin having a prenyl group at position 8.
(2S)-flavan-4-one;
4'-hydroxyflavanones;
trihydroxyflavanone
plant metabolite;
platelet aggregation inhibitor
flunarizineFlunarizine: Flunarizine is a selective calcium entry blocker with calmodulin binding properties and histamine H1 blocking activity. It is effective in the prophylaxis of migraine, occlusive peripheral vascular disease, vertigo of central and peripheral origin, and as an adjuvant in the therapy of epilepsy.diarylmethane
2-phenoxy-N-[5-(5,6,7,8-tetrahydronaphthalen-2-yl)-1,3,4-oxadiazol-2-yl]acetamidetetralins
(S)-4',5,7-Trihydroxy-6-prenylflavanoneflavanones
ith 4012
kys 05090
ulixacaltamideZ944: a T-type calcium channel antagonistbenzamides;
monochlorobenzenes;
monofluorobenzenes;
piperidines;
secondary carboxamide
non-narcotic analgesic;
T-type calcium channel blocker