In which of the following circumstances where the heart rate is increased will the cardiac output also increase
a) Moderate muscular exercise
b) Hemorrhagic shock
c) Complete heart block
d) Ventricular tachycardia
e) Cardiac failure
Answer
a. T
b. F
c. F
d. F
e. F
Discussion
a. Cardiovascular changes during exercise
- During an exercise heart rate initially increase due to psychic stimuli and later heart rate increase due to decrease vagal tone ( decrease of parasympathetic activity ) and increase sympathetic activity .
- Stroke volume also increases during exercise due to increase end diastolic volume and increase myocardial contractility (increase sympathetic action on myocardium).
- Increased HR and SV increases Cardiac output
b.heamorrhagic shock
- In hemorrhagic shock total blood volume reduces
- Venous return reduces
- End diastolic volume reduces
- Stroke volume reduces
- Cardiac output reduced
- Blood pressure = CO * TPR
- Blood pressure reduced
- The firing rate of baroreceptor reduces ( baroreceptor reflex )
- Inhibition on sympathetic discharge reduce
- Increase sympathetic discharge
- Increase heart rate
c.Complete heart block ( 3rd degree heart block )
- Type of bradycardia
- Heart rate below 60 beats per minute
d.Ventricular tachycardia
- Ventricles fill during diastole
- Increased heart rate reduces duration of diastole than the duration of systole
- Reduce ventricular filling
- Stroke volume reduces
- Cardiac output reduces
e. Cardiac failure
- In cardiac failure heart can not maintain cardiac output for adequate tissue perfusion
Labels: CVS, CVS MCQ, Physiology MCQ