sinus node
Cardiac rhythm initiator
The sinus node is a small cluster of cells in the heart's right atrium that generates electrical impulses controlling heartbeat rhythm.
Also called the sinoatrial node or SA node, it functions as the heart's natural pacemaker, setting the pace for each contraction: The sinus node fires about 60 to 100 times per minute at rest.
Loss of electrical gradient
- repolarizationMembrane voltage reset
- action potentialNeuron's rapid electrical discharge
- conductionHeat transfer through contact
- impulseSudden urge to act
automaticity · excitability · refractory period · threshold · hyperpolarization · propagation · voltage-gated
Abnormally slow heart rate
- tachycardiaExcessively fast pulse
- atrial fibrillationDisorganized cardiac rhythm disorder
- ectopicIn abnormal position
- fibrillationRapid irregular muscle contractions
flutter · syncope · pacemaker implant · ablation · dysfunction
One complete heart contraction-relaxation
- heart rateCardiac contractions per minute
- pulseArterial blood throb
- systoleHeart muscle contraction phase
- diastoleCardiac relaxation phase
contraction · rhythm · ECG · resting rate · sympathetic · parasympathetic · autonomic
Heart's venous intake chamber
- superior vena cavaMajor vein entering heart above
- myocardiumMuscular tissue of heart
- endocardiumHeart's inner wall covering
depolarization
Loss of electrical gradient
- repolarizationMembrane voltage reset
- action potentialNeuron's rapid electrical discharge
- conductionHeat transfer through contact
impulse · automaticity · excitability · refractory period · threshold · hyperpolarization · propagation · voltage-gated
bradycardia
Abnormally slow heart rate
- tachycardiaExcessively fast pulse
- atrial fibrillationDisorganized cardiac rhythm disorder
- ectopicIn abnormal position
fibrillation · flutter · syncope · pacemaker implant · ablation · dysfunction
automaticity
Self-generating action capacity
- pacemakingRegulating speed for others
cardiac cycle
One complete heart contraction-relaxation
- heart rateCardiac contractions per minute
- pulseArterial blood throb
- systoleHeart muscle contraction phase
diastole · contraction · rhythm · ECG · resting rate · sympathetic · parasympathetic · autonomic
right atrium
Heart's venous intake chamber
- superior vena cavaMajor vein entering heart above
- myocardiumMuscular tissue of heart
- endocardiumHeart's inner wall covering
node, sinuses, sinus, sinusitis, nodal, sinusoidal, sinoatrial