CTB2

Question 1

What are cardiomyocytes?

Answer 1

Specialised cardiac muscle cells responsible for heart contraction and electrical signalling.

Question 2

How do cardiomyocytes differ from skeletal muscle cells?

Answer 2

Cardiomyocytes are smaller, branched, and connected by intercalated discs, unlike skeletal muscle cells.

Question 3

What is the role of intercalated discs?

Answer 3

They connect cardiomyocytes, enabling electrical and mechanical coupling through gap junctions and desmosomes.

Question 4

What are T-tubules, and why are they important in cardiomyocytes?

Answer 4

T-tubules are invaginations of the sarcolemma that allow rapid transmission of action potentials and calcium influx.

Question 5

What is the function of the sarcoplasmic reticulum in cardiomyocytes?

Answer 5

It stores and releases calcium ions, essential for excitation-contraction coupling.

Question 6

What is excitation-contraction coupling?

Answer 6

The process by which an action potential triggers calcium release, leading to muscle contraction.

Question 7

How does calcium regulate contraction in cardiomyocytes?

Answer 7

Calcium binds to troponin, causing tropomyosin to shift and expose binding sites on actin for myosin.

Question 8

What is the role of the sinoatrial (SA) node?

Answer 8

The SA node generates the electrical impulses that initiate the heart’s rhythm.

Question 9

How does the action potential propagate in the heart?

Answer 9

It spreads from the SA node to the atria, AV node, bundle of His, bundle branches, and Purkinje fibres.

Question 10

What is the role of the atrioventricular (AV) node?

Answer 10

It delays the electrical signal to ensure atrial contraction precedes ventricular contraction.

Question 11

What are Purkinje fibres?

Answer 11

Specialised fibres that rapidly conduct electrical impulses to the ventricular myocardium.

Question 12

What is the cardiac action potential?

Answer 12

A series of voltage changes across the cardiomyocyte membrane during depolarisation and repolarisation

Question 13

What are the phases of the cardiac action potential?

Answer 13

Phase 0: Rapid depolarisation;
Phase 1: Early repolarisation;
Phase 2: Plateau;
Phase 3: Repolarisation;
Phase 4: Resting potential.

Question 14

What ion channels are involved in Phase 0 of the action potential?

Answer 14

Voltage-gated sodium channels, causing a rapid influx of Na+.

Question 15

What maintains the plateau phase (Phase 2 action potential)?

Answer 15

An influx of calcium through L-type calcium channels balances potassium efflux.

Question 16

What happens during Phase 3 (repolarisation in an action potential)?

Answer 16

Potassium efflux through K+ channels restores the resting membrane potential.

Question 17

What is the resting membrane potential of cardiomyocytes?

Answer 17

Approximately -90 mV, maintained by the sodium-potassium pump.

Question 18

What is the refractory period in cardiomyocytes?

Answer 18

The period during which a new action potential cannot be initiated, preventing arrhythmias.

Question 19

How does the autonomic nervous system regulate heart rate?

Answer 19

The sympathetic system increases heart rate via beta-adrenergic receptors, while the parasympathetic system decreases it via vagus nerve activation.

Question 20

What is inotropy?

Answer 20

The strength of cardiac muscle contraction, influenced by calcium availability.

Question 21

How does beta-adrenergic stimulation affect the heart?

Answer 21

It increases heart rate, contractility, and conduction velocity.
This happens in response to adrenaline, noradrenaline etc…

Question 22

What is the role of acetylcholine in cardiac function?

Answer 22

Acetylcholine slows heart rate by increasing K+ efflux and reducing Ca2+ influx.

Question 23

What is the role of gap junctions in cardiomyocytes?

Answer 23

They enable the rapid spread of electrical impulses between cells for synchronous contraction.

Question 24

What is the significance of pacemaker potential?

Answer 24

It ensures the SA node continuously generates rhythmic action potentials.

Question 25

How does ischemia (inadequate blood supply to tissues) affect cardiomyocyte function?

Answer 25

It reduces oxygen supply, impairing ATP production and ion pump function.

Question 26

What are the consequences of prolonged cardiac ischemia?

Answer 26

Cell death, leading to myocardial infarction and loss of contractile function.

Question 27

What is myocardial hypertrophy?

Answer 27

An increase in the size of cardiomyocytes in response to chronic pressure overload.

Question 28

How does heart failure affect excitation-contraction coupling?

Answer 28

Reduced calcium handling impairs contraction strength and efficiency.

Question 29

What is arrhythmia?

Answer 29

An abnormal heart rhythm caused by disrupted electrical activity.

Question 30

How do calcium channel blockers affect cardiac function?

Answer 30

They reduce calcium influx, lowering contractility and heart rate.

Question 31

How does hyperkalaemia (high potassium) affect cardiac action potentials?

Answer 31

It reduces the resting membrane potential, impairing excitability.

Question 32

How does hypokalaemia affect cardiac function?

Answer 32

It increases the risk of arrhythmias by prolonging repolarisation.

Question 33

What is the significance of the plateau phase in the cardiac action potential?

Answer 33

It ensures prolonged contraction for efficient blood ejection.

Question 34

What is the role of ATP in cardiomyocyte function?

Answer 34

ATP powers ion pumps, myosin-actin interactions, and calcium cycling.

Question 35

What are the electrical differences between atrial and ventricular cardiomyocytes?

Answer 35

Ventricular cells have longer action potentials to sustain contraction.

Question 36

How does exercise affect cardiomyocyte function?

Answer 36

Exercise enhances calcium cycling, contractility, and mitochondrial efficiency.

Question 37

What is the role of mitochondria in cardiomyocytes?

Answer 37

They produce ATP to meet the high energy demands of the heart.