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
Smoking is a well-established risk factor for lung cancer, and the pathophysiological process underlying this association involves the exposure of the lungs to carcinogenic agents present in tobacco smoke. Here's why option C is the correct choice:
A) Vasoconstrictive properties of nicotine reduce oxygenation and stimulate metabolism:
While nicotine is a primary addictive component of tobacco smoke and can lead to vasoconstriction, reduced oxygenation, and increased metabolism, these effects primarily contribute to cardiovascular diseases associated with smoking, such as coronary artery disease and stroke, rather than the development of lung cancer.
B) Drug addiction changes the neurochemical messages in the brain causing cravings:
This statement addresses the addictive nature of nicotine and its impact on neurochemistry, leading to cravings and dependence. While addiction is a significant aspect of tobacco use, it does not directly explain the pathophysiological process by which smoking causes lung cancer.
C) Carcinogenic agents in tobacco alter cellular cytology, morphology, and function of the lung:
Correct. Tobacco smoke contains numerous carcinogenic compounds, such as polycyclic aromatic hydrocarbons (PAHs), nitrosamines, and benzene, which can directly damage the DNA of lung cells. This DNA damage can lead to mutations and alterations in cellular cytology, morphology, and function, ultimately contributing to the development of lung cancer.
D) Risk for comorbidities increase incidence of chronic diseases and decrease longevity:
While smoking is associated with an increased risk of various comorbidities and chronic diseases, such as cardiovascular diseases, respiratory diseases, and certain cancers, this option does not specifically address the pathophysiological process of lung cancer development.
Correct Answer is D
Explanation
Hemodialysis is a renal replacement therapy used to remove waste products and excess fluid from the blood when the kidneys are unable to perform this function adequately. The physiological processes involved in hemodialysis include:
A) Solute movement toward a solution with a higher concentration:
While solute movement occurs during hemodialysis, it is typically from a solution with a higher concentration to one with a lower concentration, rather than the opposite. This movement facilitates the removal of waste products and excess solutes from the bloodstream.
B) Water movement toward a solution with a lower solute concentration:
Correct. Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. In hemodialysis, water moves out of the bloodstream, across the semipermeable membrane of the dialyzer, and into the dialysate solution, which has a lower solute concentration. This process helps remove excess fluid from the body.
C) Blood cells and protein movement through the semipermeable membrane:
Blood cells and proteins are too large to pass through the pores of the semipermeable membrane in the dialyzer during hemodialysis. Therefore, the primary exchange occurs between smaller molecules such as urea, creatinine, electrolytes, and water.
D) Osmosis of water movement and diffusion of solute movement:
Correct. Hemodialysis involves both osmosis and diffusion. Osmosis refers to the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. Diffusion is the movement of solutes from an area of higher concentration to an area of lower concentration. Together, these processes facilitate the removal of waste products and excess fluid from the bloodstream during hemodialysis.
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