CTB2 Flashcards
To learn and understand content for CTB2
What are cardiomyocytes?
Specialised cardiac muscle cells responsible for heart contraction and electrical signalling.
How do cardiomyocytes differ from skeletal muscle cells?
Cardiomyocytes are smaller, branched, and connected by intercalated discs, unlike skeletal muscle cells.
What is the role of intercalated discs?
They connect cardiomyocytes, enabling electrical and mechanical coupling through gap junctions and desmosomes.
What are T-tubules, and why are they important in cardiomyocytes?
T-tubules are invaginations of the sarcolemma that allow rapid transmission of action potentials and calcium influx.
What is the function of the sarcoplasmic reticulum in cardiomyocytes?
It stores and releases calcium ions, essential for excitation-contraction coupling.
What is excitation-contraction coupling?
The process by which an action potential triggers calcium release, leading to muscle contraction.
How does calcium regulate contraction in cardiomyocytes?
Calcium binds to troponin, causing tropomyosin to shift and expose binding sites on actin for myosin.
What is the role of the sinoatrial (SA) node?
The SA node generates the electrical impulses that initiate the heart’s rhythm.
How does the action potential propagate in the heart?
It spreads from the SA node to the atria, AV node, bundle of His, bundle branches, and Purkinje fibres.
What is the role of the atrioventricular (AV) node?
It delays the electrical signal to ensure atrial contraction precedes ventricular contraction.
What are Purkinje fibres?
Specialised fibres that rapidly conduct electrical impulses to the ventricular myocardium.
What is the cardiac action potential?
A series of voltage changes across the cardiomyocyte membrane during depolarisation and repolarisation
What are the phases of the cardiac action potential?
Phase 0: Rapid depolarisation;
Phase 1: Early repolarisation;
Phase 2: Plateau;
Phase 3: Repolarisation;
Phase 4: Resting potential.
What ion channels are involved in Phase 0 of the action potential?
Voltage-gated sodium channels, causing a rapid influx of Na+.
What maintains the plateau phase (Phase 2 action potential)?
An influx of calcium through L-type calcium channels balances potassium efflux.
What happens during Phase 3 (repolarisation in an action potential)?
Potassium efflux through K+ channels restores the resting membrane potential.
What is the resting membrane potential of cardiomyocytes?
Approximately -90 mV, maintained by the sodium-potassium pump.
What is the refractory period in cardiomyocytes?
The period during which a new action potential cannot be initiated, preventing arrhythmias.
How does the autonomic nervous system regulate heart rate?
The sympathetic system increases heart rate via beta-adrenergic receptors, while the parasympathetic system decreases it via vagus nerve activation.
What is inotropy?
The strength of cardiac muscle contraction, influenced by calcium availability.
How does beta-adrenergic stimulation affect the heart?
It increases heart rate, contractility, and conduction velocity.
This happens in response to adrenaline, noradrenaline etc…
What is the role of acetylcholine in cardiac function?
Acetylcholine slows heart rate by increasing K+ efflux and reducing Ca2+ influx.
What is the role of gap junctions in cardiomyocytes?
They enable the rapid spread of electrical impulses between cells for synchronous contraction.
What is the significance of pacemaker potential?
It ensures the SA node continuously generates rhythmic action potentials.
How does ischemia (inadequate blood supply to tissues) affect cardiomyocyte function?
It reduces oxygen supply, impairing ATP production and ion pump function.
What are the consequences of prolonged cardiac ischemia?
Cell death, leading to myocardial infarction and loss of contractile function.
What is myocardial hypertrophy?
An increase in the size of cardiomyocytes in response to chronic pressure overload.
How does heart failure affect excitation-contraction coupling?
Reduced calcium handling impairs contraction strength and efficiency.
What is arrhythmia?
An abnormal heart rhythm caused by disrupted electrical activity.
How do calcium channel blockers affect cardiac function?
They reduce calcium influx, lowering contractility and heart rate.
How does hyperkalaemia (high potassium) affect cardiac action potentials?
It reduces the resting membrane potential, impairing excitability.
How does hypokalaemia affect cardiac function?
It increases the risk of arrhythmias by prolonging repolarisation.
What is the significance of the plateau phase in the cardiac action potential?
It ensures prolonged contraction for efficient blood ejection.
What is the role of ATP in cardiomyocyte function?
ATP powers ion pumps, myosin-actin interactions, and calcium cycling.
What are the electrical differences between atrial and ventricular cardiomyocytes?
Ventricular cells have longer action potentials to sustain contraction.
How does exercise affect cardiomyocyte function?
Exercise enhances calcium cycling, contractility, and mitochondrial efficiency.
What is the role of mitochondria in cardiomyocytes?
They produce ATP to meet the high energy demands of the heart.
