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
B cells are a type of lymphocyte that originate from the bone marrow and are involved in humoral immunity.
When they encounter a foreign substance (antigen), they differentiate into plasma cells, which secrete antibodies.
Antibodies are proteins that bind to the antigen and neutralize it.
Choice A is wrong because megakaryocytes are large cells that produce platelets, not antibodies.
Choice C is wrong because antibodies are not cells, but products of plasma cells.
Choice D is wrong because T cells are another type of lymphocyte that originate from the thymus and are involved in cell-mediated immunity, not antibody production.
Correct Answer is A
Explanation
This is because anatomy and physiology are closely related branches of biology that study the structure and function of living organisms respectively.
Anatomy describes the shape, size, location, and relationships of body parts, while physiology explains how those parts work together to maintain life.
For example, the anatomy of the heart determines how it pumps blood, and the anatomy of the lungs determines how they exchange gases.
Choice B is wrong because our understanding of both anatomy and physiology is constantly changing as new discoveries are made in the field of biology.
Choice C is wrong because body parts take up space regardless of their physiological functions.
Choice D is wrong because physiological functions are not limited to an organism, but can also occur at the cellular, tissue, organ, and system levels.
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