Conduction system
This structure is the normal pacemaker of the heart and is located in the superior right atrium.
What is the sinoatrial (SA) node?
During Phase 0 of a ventricular action potential, these channels open and rapidly depolarize the cell.
What are fast sodium channels?
This ECG wave represents atrial depolarization and occurs just before atrial contraction.
What is the P wave?
This volume represents the amount of blood in the ventricle at the end of diastole and is considered a measure of preload.
What is End-Diastolic Volume ?
This factor is the difference in pressure between two ends of a blood vessel and is the primary driving force for blood flow.
What is the pressure gradient?
These specialized pathways carry impulses from the SA node to the AV node and include anterior, middle, and posterior tracts.
What are the internodal pathways?
This phase is maintained by slow calcium influx and reduced potassium efflux.
What is the plateau phase (Phase 2)?
This ECG complex represents ventricular depolarization and marks the beginning of ventricular contraction.
What is the QRS complex?
According to the Frank-Starling mechanism, an increase in venous return generally causes this ventricular performance variable to increase.
What is Stroke Volume (SV)?
Resistance to blood flow is most strongly affected by this vessel characteristic, where even small changes can produce large changes in conductance.
What is vessel radius (diameter)?
This node delays the cardiac impulse by about 0.16 seconds, allowing ventricular filling.
What is the atrioventricular (AV) node?
The resting membrane potential of ventricular muscle cells is approximately this value.
What is −80 to −90 mV?
This flat portion of the ECG reflects the delay in electrical conduction through the AV node, allowing the ventricles time to fill.
What is the PR segment?
On a pressure-volume loop, this phase occurs after the mitral valve closes but before the aortic valve opens, causing pressure to rise without a change in volume.
What is isovolumetric contraction?
Blood moving smoothly in concentric layers through a healthy vessel demonstrates this type of flow.
What is laminar flow?
These conduct impulses through the ventricles at 1.5 to 4.0 m/sec, producing nearly simultaneous ventricular activation.
What are Purkinje fibers?
This prevents a normal cardiac impulse from re-exciting already excited cardiac muscle.
What is the refractory period?
During a normal ECG, this wave represents ventricular repolarization and is usually seen as a positive deflection in Lead II.
What is the T wave?
The “lub” heard during cardiac auscultation is caused primarily by closure of these valves at the beginning of systole.
What are the atrioventricular (mitral and tricuspid) valves?
A patient with severe anemia is more likely to develop turbulent blood flow because this value increases as blood viscosity decreases
What is Reynolds number?
This occurs when a cardiac region outside the SA node develops a faster rhythm and takes control of heart pacing.
What is ectopic excitation?
During excitation-contraction coupling, calcium entering through T-tubule channels triggers release of additional calcium from this structure.
What is the sarcoplasmic reticulum?
An ECG strip shows exactly 3 large boxes between consecutive R waves. Using the box method, calculate the patient's heart rate.
What is 100 beats per minute?
A patient has an EDV of 120 mL and an ESV of 50 mL. calculate SV?
What is a stroke volume of 70 mL?
These blood vessels are the most compliant in the circulatory system and can store large volumes of blood with only small increases in pressure.
What are veins?