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Correct Answer: both a and b
sinus tachycardia refers to a condition where the heart rate exceeds the normal resting rate. generally, the heart rate in adults ranges from 60 to 100 beats per minute. when the heart rate is above 100 beats per minute, it is termed tachycardia. sinus tachycardia is a type of tachycardia that originates from the sinus node, which is the natural pacemaker of the heart responsible for setting the pace of heartbeats.
under certain circumstances, sinus tachycardia can be considered a normal physiological response rather than a pathological condition. the most common situations where sinus tachycardia is seen as normal include during physical exertion and when experiencing stress.
when a person engages in exercise, the body demands more oxygen and nutrients. to meet this increased demand, the heart rate accelerates to pump more blood to the muscles and other vital organs. this natural increase in heart rate during physical activity is a normal example of sinus tachycardia. the heart rate usually returns to normal once the physical activity ceases.
similarly, during periods of emotional or psychological stress, the body releases stress hormones such as adrenaline, which can also lead to an increase in heart rate. this response is part of the body's 'fight or flight' mechanism, preparing the individual to either face the stressor or flee from it. once the stressful situation is resolved, the heart rate typically returns to its normal pace.
therefore, in the context of the question, sinus tachycardia can be considered normal when the patient is either exercising or experiencing stress. hence, the correct answer to the question is "both a and b," indicating that both conditions can lead to a physiological, rather than pathological, increase in heart rate.
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