Which statement is true regarding myocardial functioning in the normal heart, based upon the Frank Starling law?
An increase in afterload results in decreased systolic pressure, which creates a decreased cardiac output.
A decrease in afterload causes the cardiac muscles to hypertrophy, resulting in increased diastolic volume.
An increase in preload results in greater shortening of myocardial fibers, thereby increasing contractility.
A decrease in preload results in increasing diastolic muscle fiber length, which impedes contractility.
The Correct Answer is C
A) An increase in afterload results in decreased systolic pressure, which creates a decreased cardiac output:
This statement is not consistent with the Frank-Starling law. Afterload refers to the resistance against which the heart must pump blood during systole. An increase in afterload typically results in increased systolic pressure, not decreased, as the heart works harder to overcome the increased resistance. However, increased afterload can lead to decreased cardiac output due to the increased work of the heart.
B) A decrease in afterload causes the cardiac muscles to hypertrophy, resulting in increased diastolic volume:
This statement is not consistent with the Frank-Starling law. Afterload refers to the pressure or resistance against which the heart must pump blood during systole. A decrease in afterload typically reduces the workload on the heart, which may lead to reverse remodeling and a reduction in cardiac hypertrophy. Increased diastolic volume may occur due to reduced afterload, but it's not the direct result of hypertrophy.
C) An increase in preload results in greater shortening of myocardial fibers, thereby increasing contractility:
Correct. According to the Frank-Starling law, an increase in preload (end-diastolic volume or stretch of myocardial fibers) leads to greater overlap of actin and myosin filaments within myocardial fibers during systole. This increased overlap results in stronger myocardial contraction (increased contractility), leading to an increased stroke volume and cardiac output.
D) A decrease in preload results in increasing diastolic muscle fiber length, which impedes contractility:
This statement is not consistent with the Frank-Starling law. Preload refers to the degree of stretch of the myocardial fibers at the end of diastole. A decrease in preload would lead to decreased stretch of the myocardial fibers, not increasing diastolic muscle fiber length. Decreased preload typically results in decreased contractility rather than impediment to contractility due to reduced myocardial stretch.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A) Blockage of retinal capillaries causing ischemic damage of the central macular area:
Correct. Blurry central vision that worsens over time can be indicative of macular ischemia, often caused by blockage of retinal capillaries leading to ischemic damage of the central macular area. This condition can occur in diseases such as diabetic retinopathy or retinal vein occlusion.
B) Opaque spoke-like lines developing in the periphery of the lens to the center:
This description is more characteristic of cataracts, which cause visual disturbances such as glare or halos around lights rather than blurry central vision.
C) Tears in the retina that detach from the lining of the posterior eyeball:
Retinal tears and subsequent detachment can cause visual disturbances, but they typically present as sudden onset of floaters, flashes of light, and a curtain-like shadow over the visual field rather than blurry central vision.
D) An increase in intraocular pressure with loss of peripheral vision:
This description is indicative of glaucoma, which can lead to loss of peripheral vision (visual field defects) rather than blurry central vision. Glaucoma-related visual field loss usually begins peripherally and progresses inward, affecting central vision in later stages.
Correct Answer is D
Explanation
Pressure injuries, also known as pressure ulcers or bedsores, result from prolonged pressure on the skin, leading to tissue ischemia and damage. Early recognition of the pathophysiological processes involved in pressure injury development is crucial for prevention and timely intervention. Here's why option D is the correct choice:
A) Epidermal fragility and skin excoriation with serous drainage:
This description more closely aligns with the characteristics of a superficial wound or abrasion rather than the early stages of a pressure injury. In pressure injuries, epidermal breakdown may occur later in the process, after prolonged pressure and tissue ischemia.
B) Hypodermal fluid accumulation and blister formation:
While fluid accumulation and blister formation can occur in some types of wounds, such as friction blisters or burns, they are not typically characteristic of the early stages of pressure injury development. Pressure injuries primarily involve tissue ischemia and damage due to pressure and shear forces.
C) Necrotic tissue, purulent exudate, and eschar formation:
This description is more indicative of advanced or severe pressure injuries rather than the early stages. Necrotic tissue, purulent exudate, and eschar formation typically occur in pressure injuries that have progressed to deeper tissue involvement and infection.
D) Ischemic inflammatory response marked by erythemic skin:
Correct. In the early stages of pressure injury development, the affected area may exhibit signs of tissue ischemia and inflammation, which can manifest as erythema (redness) of the skin. This erythema is a result of the body's inflammatory response to tissue damage caused by pressure and may indicate the need for intervention to relieve pressure and prevent further injury.
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