In an ECG pattern, the P wave is caused by:
Repolarization of atrial muscle fibers.
Depolarization of atrial muscle fibers.
Depolarization of ventricular muscle fibers.
Repolarization of ventricular muscle fibers.
The Correct Answer is B
This means that the electrical activity that causes the atria to contract starts from the sinoatrial node and spreads across the atria.
The P wave on the ECG reflects this atrial depolarization.
Choice A is wrong because repolarization of atrial muscle fibers is not visible on the ECG, as it occurs during the QRS complex when the ventricular depolarization masks it.
Choice C is wrong because the depolarization of ventricular muscle fibers is represented by the QRS complex on the ECG, not the P wave.
Choice D is wrong because the repolarization of ventricular muscle fibers is represented by the T wave on the ECG, not the P wave.
Normal ranges for the P wave are:
Duration: less than 0.12 seconds (less than 3 small squares)
Amplitude: less than 2.5 mm (0.25 mV) in the limb leads, less than 1.5 mm (0.15 mV) in the precordial leads
Axis: between 0° and +75°12
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Veins are the type of blood vessel that holds the greatest volume of blood and serve as reservoirs for blood.
According to 1, veins contain about 70-80% of the blood volume in circulation.
Veins are also called capacitance vessels because they can expand and store more blood when needed.
Choice A. Capillary is wrong because capillaries are very thin and narrow vessels that allow the exchange of gases and nutrients between the blood and the tissues.
Capillaries have a very small volume compared to veins.
Choice C. Arteriole is wrong because arterioles are small branches of arteries that regulate blood pressure and blood flow to the capillaries.
Arterioles have a higher resistance and lower volume than veins.
Choice D. Artery is wrong because arteries are thick and muscular vessels that carry oxygen-rich blood away from the heart to the rest of the body.
Arteries have a higher pressure and lower volume than veins.
Normal ranges for blood volume vary depending on age, sex, weight, and health status, but generally range from 4 to 6 liters for adults.
Correct Answer is A
Explanation
The right atrium receives blood directly from the superior vena cava, inferior vena cava, and coronary sinus.
The superior vena cava and inferior vena cava bring deoxygenated blood from the upper and lower body, respectively.
The coronary sinus brings blood from the heart muscle.
Choice B is wrong because it excludes the coronary sinus, which also empties into the right atrium.
Choice C is wrong because it includes the pulmonary veins, which carry oxygenated blood from the lungs to the left atrium, not the right atrium.
Choice D is wrong because it only includes the pulmonary veins, which are not connected to the right atrium at all.
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