CTB2 Flashcards

To learn and understand content for CTB2

1
Q

What are cardiomyocytes?

A

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

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2
Q

How do cardiomyocytes differ from skeletal muscle cells?

A

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

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3
Q

What is the role of intercalated discs?

A

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

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4
Q

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

A

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

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5
Q

What is the function of the sarcoplasmic reticulum in cardiomyocytes?

A

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

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6
Q

What is excitation-contraction coupling?

A

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

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7
Q

How does calcium regulate contraction in cardiomyocytes?

A

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

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8
Q

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

A

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

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9
Q

How does the action potential propagate in the heart?

A

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

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10
Q

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

A

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

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11
Q

What are Purkinje fibres?

A

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

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12
Q

What is the cardiac action potential?

A

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

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13
Q

What are the phases of the cardiac action potential?

A

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

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14
Q

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

A

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

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15
Q

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

A

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

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16
Q

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

A

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

17
Q

What is the resting membrane potential of cardiomyocytes?

A

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

18
Q

What is the refractory period in cardiomyocytes?

A

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

19
Q

How does the autonomic nervous system regulate heart rate?

A

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

20
Q

What is inotropy?

A

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

21
Q

How does beta-adrenergic stimulation affect the heart?

A

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

22
Q

What is the role of acetylcholine in cardiac function?

A

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

23
Q

What is the role of gap junctions in cardiomyocytes?

A

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

24
Q

What is the significance of pacemaker potential?

A

It ensures the SA node continuously generates rhythmic action potentials.

25
Q

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

A

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

26
Q

What are the consequences of prolonged cardiac ischemia?

A

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

27
Q

What is myocardial hypertrophy?

A

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

28
Q

How does heart failure affect excitation-contraction coupling?

A

Reduced calcium handling impairs contraction strength and efficiency.

29
Q

What is arrhythmia?

A

An abnormal heart rhythm caused by disrupted electrical activity.

30
Q

How do calcium channel blockers affect cardiac function?

A

They reduce calcium influx, lowering contractility and heart rate.

31
Q

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

A

It reduces the resting membrane potential, impairing excitability.

32
Q

How does hypokalaemia affect cardiac function?

A

It increases the risk of arrhythmias by prolonging repolarisation.

33
Q

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

A

It ensures prolonged contraction for efficient blood ejection.

34
Q

What is the role of ATP in cardiomyocyte function?

A

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

35
Q

What are the electrical differences between atrial and ventricular cardiomyocytes?

A

Ventricular cells have longer action potentials to sustain contraction.

36
Q

How does exercise affect cardiomyocyte function?

A

Exercise enhances calcium cycling, contractility, and mitochondrial efficiency.

37
Q

What is the role of mitochondria in cardiomyocytes?

A

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