Tag: heart beat

Questions Related to heart beat

Choose the correct answer from the alternatives given.
The impulses for heart beat originate in:

biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

  1. A.VN.

  2. SAN.

  3. bundles of His

  4. fibres of Purkinje

Show answer
Correct Option: B
Explanation:

The sinoatrial node (SAN) is the impulse-generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of normal sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. 

So, the correct option is 'SAN'.

State whether the following statements are true or false.
Rate of heart beat is directly proportional to the size of the body.

biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

The rate of heartbeat is inversely proportional to the size of the body. Smaller animals have a greater heart rate due to increased metabolic rate than the large animals. 

So, the correct option is 'False'.

State whether the following statements are true or false.
Valves in the cardiovascular system are found only in the heart.

biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

A valve is a membranous structure present in a hollow organ. It folds or closes to prevent the return flow of the body fluid passing through it. The valves present in between the auricles and ventricles are meant to prevent the backflow of blood from the ventricles to auricles. Valves are also a part of veins.

So, the correct option is 'False'.

Excessively high heart rate (> 180) can reduce cardiac output because 

biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

  1. Blood is moving too fast through the lungs to pick up enough oxygen

  2. It tires out the heart muscles and so they pump slower

  3. It reduces the time for ventricular filling which reduces stroke volume

  4. The PR-interval increases which leads to longer ventricular diastole and shorter ventricular systole

Show answer
Correct Option: C
Explanation:

Heart rate affects both stroke volume and minute volume by altering the length of diastole and thereby the degree of filling and force of contraction. Minute volume and B.P may rise even if the stroke volume falls. This happens with a moderate rise in the heart rate. But if the heart rate is too high, the stroke volume becomes so low that the minute output falls far below the normal.

During muscular exercise, the output may be 30-40 litres i.e., 6-10 times the normal minute volume( stroke volume 170-200 ml; heart rate 150-180 per minute).
So, the correct answer is 'It reduces the time for ventricular filling which reduces stroke volume'.

Bicuspid and tricuspid valves are open during

biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

  1. Ventricular systole

  2. Ventricular diastole

  3. Atrial systole

  4. Late joint diastole

Show answer
Correct Option: C
Explanation:

Atrial systole occurs at the end of ventricular diastole. After the ventricle has pumped its blood, it begins to relax. There is now negative pressure in the ventricle (since it is now empty), and this pressure helps to draw in the blood from the atrium when it enters into systole. So during atrial systole, the bicuspid and tricuspid valves are open, and the pulmonary/aortic semilunar valves are closed. Then during the diastole, the bicuspid and tricuspid valves are closed.