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 C
Explanation
Renal calculi, also known as kidney stones, are solid masses made up of crystals that form in the kidneys due to various factors, including supersaturation of urine with stone-forming substances, inadequate urine volume, and conditions that promote crystal precipitation and retention in the urinary tract. Here's the breakdown of the pathological process contributing to the client's clinical presentation:
A) Excessive urine output:
Excessive urine output (polyuria) is not typically associated with the formation of renal calculi. In fact, low urine output (oliguria) or concentrated urine may increase the risk of stone formation by reducing the volume of urine available to dilute stone-forming substances.
B) Excessive fluid intake:
Excessive fluid intake is generally beneficial in preventing kidney stone formation by increasing urine volume and diluting stone-forming substances. Therefore, it is not likely to contribute to the development of renal calculi in this scenario.
C) Increased calcium reabsorption:
Correct. Increased calcium reabsorption in the renal tubules can lead to hypercalcemia and hypercalciuria, which are risk factors for the formation of calcium-containing kidney stones (calcium oxalate or calcium phosphate stones). Excessive calcium reabsorption may occur due to various factors, including hormonal imbalances (e.g., hyperparathyroidism) or medications that affect calcium metabolism.
D) Increased serum alkalinity:
Increased serum alkalinity (alkalosis) is not typically associated with the formation of renal calculi. Urinary pH may influence the formation of certain types of kidney stones (e.g., uric acid stones are more likely to form in acidic urine), but alkalosis alone is not a primary factor in stone formation.
Correct Answer is A
Explanation
A) Flank pain and profound hypotension:
Correct. Flank pain, often described as a deep, constant, gnawing, or throbbing sensation in the abdomen or back, can be a sign of impending rupture or dissection of an abdominal aortic aneurysm (AAA). Profound hypotension may occur if the AAA ruptures, leading to massive internal bleeding and shock. Prompt recognition of these signs is crucial for early intervention and surgical repair to prevent catastrophic consequences.
B) Acute shortness of breath and chest pain:
Acute shortness of breath and chest pain are more indicative of cardiovascular or pulmonary conditions such as myocardial infarction, pulmonary embolism, or acute coronary syndrome rather than an abdominal aortic aneurysm. While aortic dissection can present with chest pain, it is typically described as severe, tearing, or ripping pain that radiates to the back, not as acute shortness of breath.
C) Absent pedal pulses and darkened toes:
Absent pedal pulses and darkened toes may indicate peripheral vascular disease or critical limb ischemia but are not specific signs of an abdominal aortic aneurysm. While AAA can lead to peripheral ischemia in advanced cases, it is not typically associated with acute changes in pedal pulses or toe discoloration.
D) Tea-colored urine and decreased output:
Tea-colored urine and decreased urine output may indicate acute kidney injury or rhabdomyolysis but are not specific signs of an abdominal aortic aneurysm. While a ruptured AAA can lead to renal ischemia and acute kidney injury due to hypoperfusion, these symptoms are not the primary manifestations of AAA
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