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
Cardiac output is calculated by multiplying the stroke volume by the heart rate, not by the systolic blood pressure.
Stroke volume is the amount of blood circulated by the heart with each beat. Heart rate is the number of beats per minute.
Systolic blood pressure is the pressure in the arteries when the heart contracts. Choice A is wrong because it confuses systolic blood pressure with heart rate.
Systolic blood pressure is not directly related to cardiac output, although it can be affected by it.
1: Cardiac Output- Definition, Factors Affecting, Cardiac Index - BYJU’S 2: Cardiac Output (Fick’s Formula) - MDCalc 3: Calculating how much blood is pumped by the heart - Cellular respiration and transport - Edexcel - GCSE Biology (Single Science) Revision - Edexcel - BBC Bitesize 4: Cardiac output - Structure and function of the heart - Higher Human Biology Revision - BBC Bitesize : Blood Pressure: What Is Normal? How To Measure Blood Pressure (healthline.com)
Correct Answer is B
Explanation
A hormone is a secreted molecule that is carried in the bloodstream to where it acts on target cells that bear specific receptors for that hormone.
This definition is consistent with the dictionary and encyclopedia sources.
Choice A is wrong because it contradicts the definition of a hormone.
Hormones are not just any secreted molecules, but ones that have specific effects on cells with matching receptors.
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