The term used to describe the relaxation of the myocardium to allow ventricles to fill with blood is:
stroke volume.
afterload.
systole.
diastole.
The Correct Answer is D
Choice A rationale
Stroke volume is the amount of blood ejected by the left ventricle in one single contraction. It is the difference between end-diastolic volume and end-systolic volume. While it depends on the filling that occurs during relaxation, it is a measure of output rather than the state of the muscle during the filling phase. Normal stroke volume is approximately 60 to 100 mL per beat. Factors affecting stroke volume include preload, myocardial contractility, and the systemic resistance or afterload.
Choice B rationale
Afterload is the resistance the heart must pump against to eject blood into the systemic circulation. It is primarily determined by the diameter of the arterioles and the pressure in the aorta. Afterload occurs during the systolic phase of the cardiac cycle when the ventricles are contracting, not during the relaxation phase. High afterload increases the workload of the heart and can lead to ventricular hypertrophy over time if the condition remains chronic or is left untreated.
Choice C rationale
Systole is the phase of the cardiac cycle when the heart muscle contracts and pumps blood from the chambers into the arteries. During ventricular systole, the mitral and tricuspid valves close, and the aortic and pulmonary valves open. This is the period of high pressure and active work. Systole is the opposite of relaxation; it is the time of ejection. A normal systolic blood pressure for an adult is generally considered to be less than 120 mmHg.
Choice D rationale
Diastole is the period of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood. During ventricular diastole, the ventricles expand to receive blood from the atria. This relaxation is essential for adequate preload and subsequent cardiac output. Diastole encompasses both the early rapid filling phase and the atrial kick. Normal diastolic pressure is less than 80 mmHg. Proper diastolic function ensures the myocardium receives adequate coronary perfusion, which mostly occurs when the muscle is relaxed.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
The motor pathways in the brain, specifically the corticospinal tract, undergo decussation or crossing over at the level of the medulla oblongata. This means that the motor neurons originating in the left hemisphere of the brain control the muscle movements on the right side of the body. When a stroke occurs in the left hemisphere, the resulting damage to these neurons manifests as contralateral weakness or paralysis on the right side.
Choice B rationale
Due to the contralateral organization of the central nervous system, injury to the left side of the brain does not typically result in isolated weakness on the same side. Ipsilateral weakness would only occur if the damage was below the point of decussation in the spinal cord. In the context of a hemispheric stroke, the physical deficits appear on the opposite side of the brain lesion. Therefore, left sided weakness would indicate a right hemisphere stroke.
Choice C rationale
A stroke involving the left hemisphere typically impacts the primary motor cortex or the internal capsule, which are essential for voluntary movement. It is medically expected that such an event will produce some level of neurological deficit unless the stroke was extremely small or located in a non functional area. Weakness or paralysis is a classic symptom of middle cerebral artery strokes. Suggesting that no side is affected ignores the basic principles of clinical neurology.
Choice D rationale
Weakness on both sides of the body, or quadriparesis, usually indicates a lesion in the brainstem or a very large bilateral injury, rather than a stroke confined to the left hemisphere. The brainstem contains the motor pathways for both sides before they fully separate or decussate. A focal stroke in one hemisphere is characterized by hemiparesis or hemiplegia, affecting only one half of the body. Bilateral weakness is not a standard expectation for a unilateral hemispheric stroke.
Correct Answer is D
Explanation
Choice A rationale
This sequence incorrectly places the bicuspid valve between the right atrium and right ventricle. In the human heart, the tricuspid valve is the structure that separates the right-sided chambers, while the bicuspid or mitral valve is strictly located on the left side. Furthermore, this choice suggests the tricuspid valve is on the left, which reverses the actual anatomical and physiological flow required for effective pulmonary and systemic circulation through the four cardiac chambers.
Choice B rationale
This pathway is incorrect because it suggests that venous blood from the vena cavae enters the left atrium. Deoxygenated blood from the systemic circulation must enter the right atrium first. Additionally, it lists the tricuspid valve on the left side and the bicuspid valve on the right side. This reverses the entire cardiac anatomy, which would prevent the separation of oxygenated and deoxygenated blood, leading to a total failure of the respiratory and circulatory systems.
Choice C rationale
This description is physiologically impossible as it starts by sending systemic venous blood to the left atrium. The left side of the heart is responsible for receiving oxygenated blood from the lungs via the pulmonary veins, not deoxygenated blood from the vena cavae. It also incorrectly lists the aortic valve before the pulmonary artery and the pulmonic valve before the aorta. This sequence ignores the pressure gradients and valve functions necessary for maintaining unidirectional blood flow.
Choice D rationale
This sequence correctly follows the physiological path of blood. Deoxygenated blood enters the right atrium from the body, passes through the tricuspid valve into the right ventricle, and is pumped through the pulmonic valve to the lungs. After gas exchange, oxygenated blood returns via pulmonary veins to the left atrium, moves through the bicuspid valve to the left ventricle, and is ejected through the aortic valve into the aorta for systemic distribution. This represents the accurate anatomical circuit.
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