Fundamentals of Nursing Q 4


All of the following can cause tachycardia except:
  
     A. Fever
     B. Exercise
     C. Sympathetic nervous system stimulation
     D. Parasympathetic nervous system stimulation
    
    

Correct Answer: D. Parasympathetic nervous system stimulation
Parasympathetic nervous system stimulation of the heart decreases the heart rate as well as the force of contraction, rate of impulse conduction and blood flow through the coronary vessels. Fever, exercise, and sympathetic stimulation all increase the heart rate. The parasympathetic nervous system (PNS) releases the hormone acetylcholine to slow the heart rate. Such factors as stress, caffeine, and excitement may temporarily accelerate your heart rate, while meditating or taking slow, deep breaths may help to slow your heart rate.
Option A: Tachypnea and tachycardia develop, and the patient becomes dehydrated because of sweating and vapor losses from the increased respiratory rate. Many manifestations of fever are related to the increased metabolic rate, increased need for oxygen, and use of body proteins as an energy source.
Option B: Often, ventricular tachycardia will occur during the recovery period post exercise due to increased levels of adrenaline. In a study conducted in 1991, it was found that 70% of patients tested experienced idiopathic ventricular tachycardia as a result of exercise. Exercising for any duration will increase your heart rate and will remain elevated for as long as the exercise is continued. At the beginning of exercise, your body removes the parasympathetic stimulation, which enables the heart rate to gradually increase. As you exercise more strenuously, the sympathetic system “kicks in” to accelerate your heart rate even more.
Option C: Heart rate is controlled by the two branches of the autonomic (involuntary) nervous system. The sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The sympathetic nervous system (SNS) releases the hormones (catecholamines – epinephrine and norepinephrine) to accelerate the heart rate.