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 D
Explanation
The systemic circuit sends oxygen-rich blood to the tissues.
It is part of the circulatory system that carries blood away from the heart, delivers it to most of the organs and tissues, and returns it to the heart again.
Choice A is wrong because it describes the pulmonary circuit, which brings oxygen-poor blood from the heart to the lungs.
Choice B is wrong because it is the opposite of what the systemic circuit does.
The systemic circuit brings oxygen-rich blood from the heart to the tissues, not from the tissues.
Choice C is wrong because it is also the opposite of what the systemic circuit does. The systemic circuit sends oxygen-poor blood to the heart, not from the heart.
Correct Answer is C
Explanation
A newborn is protected against certain digestive and respiratory infections by IgA received via the mother’s milk.
IgA is the main antibody found in breast milk, and it coats and seals the baby’s respiratory and intestinal tract to prevent germs from entering the body and bloodstream.
Choice A is wrong because the blood does not contain IgA, which is the main antibody that protects mucosal membranes.
Choice B is wrong because the placenta does not transfer IgA to the fetus, but only some other antibodies such as IgG.
Choice D is wrong because the intestine does not produce IgA in newborns, as they are born with low levels of IgA.
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