2020 - Heart physiology 1

What is the function of valves in the heart?

• promote contraction of ventricles

• prevent backflow of blood through the heart

• eliminate pressure variances within the heart

• allow oxygen to diffuse into the heart

The rapid influx of calcium ions into pacemaker cells creates a positive membrane potential inside the cell and is responsible for the:

• minimum potential phase

• repolarization phase

• full depolarization phase

• slow initial repolarization phase

What ion movement changes the membrane potential in a contractile cell from negative to positive during the rapid depolarization phase?

• influx of sodium ions

• outflow of potassium ions

• outflow of calcium ions

• influx of calcium ions

During what phase of the action potential will calcoum ions enter the contractile cell as potassium exits?

• rapid depolarization phase

• initial repolarization phase

• repolarization phase

• plateau phase

The long length of the cardiac action potential, at 200-300 msec, allows for:

• a reduction in the strength of heart contraction

• less calcium ions to enter cells

• a faster heart rate

• an opportunity for the heart to fill with blood

On an ECG, a damaged AV node will primarily affect the length of the:

• P wave

• P-R interval

• T wave

• Q-T interval

What activity is occurring in the heart during the Q-T interval on an ECG?

• The atrial cells are undergoing action potentials

• The ventricular cells are repolarizing

• The AV node delay

• The ventricular cells are undergoing action potentials