The Human Heart and Cardiac Cycle

Question 1

In which specific region of the thoracic cavity is the heart located?

Accepted Answer

The mediastinum

Question 2

What is the name of the tough, protective membrane that surrounds and protects the heart?

Accepted Answer

The pericardium (or pericardial sac)

Question 3

Which layer of the heart wall is composed of cardiac muscle cells and performs the pumping action?

Accepted Answer

Myocardium

Question 4

Contrast the oxygen levels in pulmonary arteries versus pulmonary veins.

Accepted Answer

Arteries: deoxygenated; Veins: oxygenated

Question 5

What is the primary function of the chordae tendineae and papillary muscles?

Accepted Answer

Preventing atrioventricular valve eversion (prolapse) during ventricular contraction

Question 6

Which valve prevents the backflow of blood from the aorta into the left ventricle?

Accepted Answer

Aortic semilunar valve

Question 7

What property allows cardiac muscle to initiate its own electrical impulse at a fixed rate?

Accepted Answer

Autorhythmicity

Question 8

Which component of the intercalated disc allows ions to flow between cells to synchronize contraction?

Accepted Answer

Gap junctions

Question 9

Why does cardiac muscle require a significantly longer refractory period than skeletal muscle?

Accepted Answer

To prevent tetany (sustained contraction), which would stop pumping

Question 10

Which structure serves as the primary pacemaker of the heart?

Accepted Answer

Sinoatrial (SA) node

Question 11

What is the functional purpose of the 100 ms delay at the atrioventricular (AV) node?

Accepted Answer

Allows atria to finish contracting and filling ventricles

Question 12

Identify the path of an electrical impulse after it leaves the AV bundle (Bundle of His).

Accepted Answer

Left and right bundle branches, then Purkinje fibers

Question 13

On an ECG, what electrical event does the P wave represent?

Accepted Answer

Atrial depolarization

Question 14

Why is atrial repolarization not visible on a standard ECG tracing?

Accepted Answer

It is masked by the larger QRS complex (ventricular depolarization)

Question 15

Cardiac Cycle — Define 'systole'.

Accepted Answer

The period of heart muscle contraction and blood pumping

Question 16

What term describes the 20–30% of ventricular filling provided by atrial contraction?

Accepted Answer

Atrial kick

Question 17

Define End Diastolic Volume (EDV).

Accepted Answer

Total blood in ventricles at the end of atrial systole (preload)

Question 18

What happens to heart valves during the 'isovolumic contraction' phase?

Accepted Answer

All valves (AV and semilunar) are closed

Question 19

What physical event produces the S1 ('lub') heart sound?

Accepted Answer

Closing of the atrioventricular (mitral and tricuspid) valves

Question 20

What produces the S2 ('dub') heart sound?

Accepted Answer

Closing of the semilunar (aortic and pulmonary) valves

Question 21

Cardiac Output — What two variables are multiplied to calculate this value?

Accepted Answer

Heart rate (HR) and Stroke volume (SV)

Question 22

How is Stroke Volume (SV) calculated using ventricular volumes?

Accepted Answer

$$SV = EDV - ESV$$

Question 23

What is the clinical definition of bradycardia in an adult?

Accepted Answer

Resting heart rate below 60 bpm

Question 24

What is the clinical definition of tachycardia in an adult?

Accepted Answer

Resting heart rate above 100 bpm

Question 25

Where are the cardioaccelerator and cardioinhibitory centers located in the brain?

Accepted Answer

Medulla oblongata