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 A
Explanation
It is a major component of the lymphatic system and contains T and B lymphocytes.
Choice B is wrong because the spleen does not produce T lymphocytes, but rather stores them.
T lymphocytes are produced in the thymus.
Choice C is wrong because the spleen does not filter lymph, but rather blood. It traps bloodborne microbes and produces an immune response to them.
Choice D is wrong because the spleen consists of one lobe and is located in the upper left abdomen below the diaphragm.
The description in choice D matches the thymus, not the spleen.
The normal size of the spleen in adults is about 12 cm long, 8 cm broad, and 3-4 cm thick, weighing about 200 g.
The normal range of splenic index (the product of length, width, and thickness) is 120-480 cm.
Correct Answer is A
Explanation
Excretion is the process of removing metabolic wastes or excrements from the body.
Metabolic wastes are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism and must therefore be excreted.
These include nitrogen compounds, water, CO2, phosphates, sulphates, etc.
Choice B. Absorption is wrong because absorption is the process of taking in substances into the body or cells.
It is not related to the removal of waste.
Choice C. Metabolism is wrong because metabolism is the sum of all the chemical reactions that occur in an organism.
It is not a process of removing wastes, but rather producing them.
Choice D. Assimilation is wrong because assimilation is the process of incorporating substances into the body or cells.
It is also not related to the removal of waste.
Normal ranges for metabolic wastes vary depending on the type and concentration of the waste, as well as the organism and its environment.
For example, ammonia is a very toxic waste that requires a lot of water for its excretion, while uric acid is a less toxic waste that can be concentrated into a small volume.
Some normal ranges for human metabolic wastes are:
Urea: 2.5 to 6.4 mmol/L in blood serum Uric acid: 3.4 to 7.2 mg/dL in blood serum Creatinine: 0.6 to 1.2 mg/dL in blood serum CO2: 35 to 45 mmHg in arterial blood gas
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