Cardiac Physiology

In resting conditions, which of the following channels is most likely open in a cardiac myocyte?

• Sodium channels

• Calcium channels

• Chloride channels

• Potassium channels

What is the usual resting membrane potential for ventricular myocytes?

• 90 mV

• • 
    -90 mV

• 75 mV

• -60 mV

What is the role of the atrioventricular (AV) node in the cardiac conduction system?

• Initiation of the action potential

• Regulation of heart rate

• Conduction delay to allow atria to contract before ventricles

• Control of blood pressure

Where does the inferior vena cava drain?

• lingula

• right atrium

• right ventricle

• left atrium

Which vessels drain into the left atrium?

• pulmonary veins

• pulmonary arteries

• inferior and superior vena cava

• bronchial veins

Which of the following is the depolarization phase of the action potential in pacemaker cells?

• Phase 3

• Phase 0

• Phase 1

• Phase 4

What is the length of a normal PR interval?

• 0.06 to 0.3 seconds

• 0.12 to 0.2 seconds

• 0.08 to 0.2 seconds

• 0.08 to 0.1 seconds

Where is the unipolar chest lead V4 placed?

• 6th intercostal space at the left midaxillary line

• 5th intercostal space at the left midclavicular line

• 3rd intercostal space right of the sternum

• 2nd intercostal space left of the sternum

Which of the following ECG findings is typically associated with the unipolar limb lead AVR?

• The QRS complex is always upright.

• Tall R wave

• Small P wave

• • 
    Negative P wave

Which of the following influences the corrected QT (QTc)?

• Heart rate

• Blood oxygenation

• Respiratory rate

• Blood pressure