IB Biology Option D(4) - Cardiac Cycle

Which of the following are true in the cardiac cycle?

I. The SAN creates a delay before sending out impulses along the Bundle of His

II. Electrical impulses pass from Purkinje fibres to the ventricles walls and apex

III. Fibrous tissue between atria and ventricles prevent electrical impulses passing between them

• I and II only

• I and III only

• II and III only

• I, II and III

Which of the following contribute(s) to the ventricles only contracting when the atria have fully contracted?

I. Fibrous tissue between atria and ventricles

II. There is a delay before the AV node sends out impulses

III. A wave of contraction passes upwards from the apex of the heart

• I only

• II only

• I and II only

• I, II and III

Which of the following is the correct route taken by electrical impulses within the heart?

• AVN --> SAN --> Bundle of His --> Purkinje fibres --> Ventricle Walls

• AVN --> SAN --> Purkinje fibres --> Bundle of His --> Ventricle Walls

• SAN --> AVN --> Bundle of His --> Purkinje fibres --> Ventricle Walls

• SAN --> AVN --> Purkinje fibres --> Bundle of His --> Ventricle Walls

What is/are the advantage(s) of electrical impulses passing to the apex of the heart?

I. A wave of contraction passes upwards

II. The heart contracts from the apex upwards

III. Blood is forced at high pressure into veins

• I and II only

• I and III only

• II and III only

• I, II and III

Which of the following is true about the semi-lunar valves in the heart?

• They are between atria and ventricles

• They close when pressure in the arteries is higher than pressure in the atria

• They prevent backflow of blood into the atria

• They open when pressure in the ventricles is higher than pressure in the arteries

What is the role of fibrous tissue in the heart between the atria and ventricles?

• It transmits impulses from the SAN to the AVN

• It transmits impulses from the AVN to the Bundle of His

• It transmits impulses from Bundle of His to Purkinje fibres

• It prevents impulses being transmitted from atria to ventricles

The picture shows an electrocardiagram (ECG).

Which of the following are true of this ECG?

I. Depolarization happens at P, R and T

II. The SAN is responsible for the P wave

III. The R wave causes ventricles to contract

• I and II only

• I and III only

• II and III only

• I, II and III

Which is true of an ECG of a person who has arrhythmia?

• The R wave will be shorter in height

• The T wave will be wider

• The distance between R waves can be different

• The P wave will be shorter in height

Which is the best definition of ventricular fibrillation?

• ventricles contract more forcefully

• ventricles stop contracting

• ventricles contract simultaneously

• ventricles contract unsynchronised

The time delay between two successive R waves on a normal ECG is 1.2 seconds.

What is the heart rate of this person, in beats per minute?

• 50

• 60

• 65

• 70