IB Biology Topic 6.2

What type of muscle is found in the heart?

• skeletal

• smooth

• voluntary

• cardiac

In the section of cardiac muscle shown, structures A and B respectively are

• mitochondrion, intercalated disc

• mitochondrion, myosin/actin filaments

• nucleus, intercalated disc

• nucleus, myosin/actin filaments

What is a similarity between cardiac and skeletal muscle?

• both are striated

• both fatigue

• both multinucleate

• both under voluntary control

Which is correct about the SA node?

• located in left atrium

• a collection of cardiac cells initiating action potentials

• referred to as the artificial pacemaker

• it is the equivalent of the AV node in birds

In general, what is systole?

• contraction

• the same as diastole

• relaxation

• the system of blood vessels in the heart

Where is the AV node?

• in the left atrium wall

• junction between the atria and ventricles

• in the right atrium wall

• in the ventricles

What is the correct sequence of electrical signals spreading throughout the heart?

• SA node→bundle of His→AV node→Purkinje fibres

• SA node→AV node→Purkinje fibres→bundle of His

• SA node→AV node→bundle of His→Purkinje fibres

• AV node→SA node→bundle of His→Purkinje fibres

What causes the "lub" sound?

• AV valves closing

• AV valves opening

• semilunar valves closing

• semilunar valves opening

An artificial pacemaker would be beneficial for which one of the following conditions?

• obesity

• inability of brain to send rhythmic signals to the hear

• malfunctioning SA node

• narrowing of coronary arteries

During diastole which one of the following is not occurring?

• semilunar valves are closed

• both atria and ventricles are relaxed

• "dub" sound is made

• only ventricles are relaxed, atria are contracting