The normal pacemaker of the heart is the:
Purkinje fibers.
AV bundle.
Sinoatrial node.
Atrioventricular node.
The Correct Answer is C
The sinoatrial (SA) node is the natural pacemaker of the heart.
It generates electrical impulses that cause the heart’s chambers to contract, setting the heart rate.
The SA node typically generates 60–100 heartbeats per minute when a person is at rest.
Choice A is wrong because Purkinje fibers are part of the electrical conduction system of the heart that carries impulses to the ventricles.
They are not the primary source of impulses.
Choice B is wrong because the AV bundle (also called bundle of His) is another part of the electrical conduction system of the heart that connects the atria and the ventricles.
It is not the natural pacemaker of the heart.
Choice D is wrong because an atrioventricular node is a relay station between the atria and the ventricles that delays the electrical impulses from the SA node.
It can act as a backup pacemaker if the SA node fails, but it is not the normal pacemaker of the heart.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
The antibodies produced in allergic reactions belong to the immunoglobulin E group.
These antibodies bind to an allergen, triggering a release of histamine, which causes allergy symptoms.
They also help to fight parasitic infections.
Choice B is wrong because allergens are not antibodies, but substances that cause an allergic reaction.
Choice C is wrong because the antibodies that belong to the immunoglobulin G group are not involved in allergic reactions, but in fighting bacterial and viral infections.
Choice D is wrong because mast cells are not antibodies, but cells that release histamine and other chemicals when activated by IgE antibodies.
Correct Answer is B
Explanation
Naturally acquired active immunity is the type of resistance that is acquired as a result of developing a disease.
This means that the immune system produces antibodies to fight off the infection and remembers the pathogen for future protection.
This type of immunity is long-lasting and sometimes life-long.
Choice A is wrong because naturally acquired passive immunity is the type of resistance that is acquired when a person receives antibodies from another source, such as from the mother through the placenta or breast milk.
This type of immunity is temporary and lasts only for a few weeks or months.
Choice C is wrong because artificially acquired active immunity is the type of resistance that is acquired when a person receives a vaccine that contains a weakened or killed form of the disease organism.
This triggers the immune system to produce antibodies and memory cells without causing the actual disease.
This type of immunity can last for years or decades, depending on the vaccine.
Choice D is wrong because artificially acquired passive immunity is the type of resistance that is acquired when a person receives antibody-containing blood products, such as immune globulin, that provide immediate protection from a specific disease.
This type of immunity is also temporary and lasts only for a few weeks or months.
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