cardio 3

Question 1

What are the learning outcomes of Cardiovascular Physiology 3?

Answer 1

Understand how action potentials evoke contraction in cardiomyocytes and relate pressure/volume changes to ECG and heart sounds.

Question 2

What triggers muscle contraction in cardiomyocytes?

Answer 2

Action potentials that lead to calcium influx.

Question 3

What are L-type calcium channels?

Answer 3

Voltage-gated channels on the T-tubules that open during depolarisation to allow Ca²⁺ entry.

Question 4

What is calcium-induced calcium release?

Answer 4

Initial Ca²⁺ influx triggers RyR receptors on the SR to release more Ca²⁺.

Question 5

What is the role of SERCA?

Answer 5

ATP-dependent pump that reuptakes Ca²⁺ into the SR.

Question 6

How does NCX (Na⁺/Ca²⁺ exchanger) function?

Answer 6

Exports 1 Ca²⁺ out in exchange for 3 Na⁺ in.

Question 7

What does PMCA do?

Answer 7

Uses ATP to pump Ca²⁺ out of the cell into the extracellular space.

Question 8

How do mitochondria handle calcium?

Answer 8

Via a uniporter and exchangers; calcium entry boosts ATP production.

Question 9

Why is the Na⁺/K⁺ ATPase important?

Answer 9

Maintains Na⁺ gradient needed for NCX function.

Question 10

What happens when Ca²⁺ binds troponin C?

Answer 10

Conformational change moves tropomyosin, exposing actin binding sites.

Question 11

What is a cross-bridge in muscle contraction?

Answer 11

Myosin head (with ADP+Pᵢ) binds exposed actin site.

Question 12

What is the power stroke?

Answer 12

Myosin pivots, pulling actin and releasing ADP+Pᵢ.

Question 13

How does cross-bridge detach?

Answer 13

ATP binds to myosin, causing it to detach.

Question 14

What re-cocks the myosin head?

Answer 14

ATP hydrolysis resets myosin to high-energy state.

Question 15

What ends contraction?

Answer 15

Ca²⁺ is removed; troponin releases Ca²⁺ and tropomyosin re-blocks actin.

Question 16

What is troponin T used for clinically?

Answer 16

Blood marker of heart muscle damage, e.g., heart attack.

Question 17

What does the P wave represent?

Answer 17

Atrial depolarisation.

Question 18

What happens after the P wave?

Answer 18

Atrial contraction increases atrial pressure and ventricular filling.

Question 19

What does the QRS complex represent?

Answer 19

Ventricular depolarisation.

Question 20

Why doesn’t ventricular volume change immediately after QRS?

Answer 20

AV valves close; pressure rises with no volume change (isovolumetric contraction).

Question 21

What causes the S1 heart sound?

Answer 21

Closure of atrioventricular (AV) valves.

Question 22

When does blood eject into the aorta?

Answer 22

When ventricular pressure exceeds aortic pressure.

Question 23

What is stroke volume?

Answer 23

The volume of blood ejected per beat (≈70 mL).

Question 24

What does the T wave represent?

Answer 24

Ventricular repolarisation and start of relaxation.

Question 25

What causes the S2 heart sound?

Answer 25

Closure of the aortic valve.

Question 26

When does ventricular filling begin?

Answer 26

When ventricular pressure falls below atrial pressure and AV valves open.

Question 27

What percent of ventricular filling is passive?

Answer 27

≈80%; atrial contraction contributes only ≈20%.

Question 28

What is atrial fibrillation?

Answer 28

Atria quiver without contracting, impairing full ventricular filling.

Question 29

What serious risk does atrial fibrillation pose?

Answer 29

Stroke, due to clot formation in the atria.

Question 30

Why is understanding this cycle important clinically?

Answer 30

It informs diagnosis and treatment of cardiac diseases, including heart attacks and arrhythmias.