CVD WK 4 Cardiac and vascular physiology 1

Which chamber receives deoxygenated blood from the body?

Right atrium (via superior and inferior vena cava)

Which chamber pumps blood to the lungs?

Right ventricle (via pulmonary artery)

Which chamber receives oxygenated blood from the lungs?

Left atrium (via pulmonary veins)

Which chamber pumps blood to the body?

Left ventricle (via aorta)

Which ventricle has a thicker wall and why?

Left ventricle - pumps blood to the entire body at higher pressure

Which valve is between the right atrium and right ventricle?

Tricuspid valve (three cusps)

Which valve is between the left atrium and left ventricle?

Bicuspid (Mitral) valve (two cusps)

What prevents AV valves from flipping backward?

Chordae tendineae and papillary muscles

Which valve is between the left ventricle and the aorta?

Aortic valve (semilunar)

Which valve is between the right ventricle and the pulmonary artery?

Pulmonary valve (semilunar)

Do semilunar valves use chordae tendineae?

No - they open and close passively

What is systole?

Contraction and emptying of the ventricles

What is diastole?

Relaxation and filling of the ventricles

What happens during isovolumetric ventricular contraction?

Ventricles contract with all valves closed - pressure builds but no blood ejected

What is End Diastolic Volume (EDV)?

Volume of blood in the ventricle at the end of diastole (~120-130 mL)

What is End Systolic Volume (ESV)?

Volume of blood in the ventricle at the end of systole (~50-60 mL)

What is Stroke Volume (SV)?

EDV - ESV (~70 mL per beat)

What is Ejection Fraction?

SV / EDV (normal ~55-65%)

What are intercalated discs?

Junctions between cardiomyocytes containing desmosomes and gap junctions

What are gap junctions made of?

Connexin43 proteins

What do gap junctions allow?

Electrical coupling between cardiomyocytes - heart acts as a functional syncytium

What is the primary pacemaker of the heart?

SA node (Sinoatrial node) - fires 60-100 bpm

What is the function of the AV node?

Slows the signal - ensures atria finish contracting before ventricles start

What is the function of the Bundle of His?

Pathway from AV node into ventricles - splits into left and right bundle branches

What is the function of Purkinje fibres?

Conduct action potential rapidly through the ventricles - ventricles contract in unison

What channels cause the pacemaker potential in SA node cells?

Funny channels (If) - slow Na+ influx

What causes the upstroke in SA node cells?

L-type Ca2+ channels open - rapid Ca2+ influx

What is the difference between T-type and L-type Ca2+ channels?

T-type = transient (small), L-type = long-lasting (large)

What happens if the SA node fails?

AV node takes over as pacemaker (slower rate ~50 bpm)

What is an ectopic focus?

An abnormal pacemaker that fires faster than the SA node - causes arrhythmia

What causes rapid depolarisation (Phase 0) in contractile cells?

Fast voltage-gated Na+ channels open - rapid Na+ influx

What causes the plateau phase (Phase 2) in contractile cells?

L-type Ca2+ channels open - Ca2+ influx balanced by K+ efflux

What causes repolarisation (Phase 3) in contractile cells?

L-type Ca2+ channels close, delayed rectifier K+ channels open - K+ efflux dominates

What is unique about the cardiac action potential?

The plateau phase - prevents tetany

What triggers calcium release from the SR?

Ca2+ entering via L-type channels (calcium-induced calcium release)

What receptor on the SR releases Ca2+?

Ryanodine receptor (RyR)

What pumps Ca2+ back into the SR?

SERCA (Sarco/Endoplasmic Reticulum Ca2+ ATPase)

What does the P wave on an ECG represent?

Atrial depolarisation

What does the QRS complex on an ECG represent?

Ventricular depolarisation

What does the T wave on an ECG represent?

Ventricular repolarisation

What are the three layers of the heart wall?

Endocardium (inner), Myocardium (middle), Epicardium (outer)

What is pericarditis?

Inflammation of the pericardium - painful friction

Which muscle type has intercalated discs?

Cardiac muscle

Which muscle type is voluntary?

Skeletal muscle

Which muscle type has no striations?

Smooth muscle

What does Ca2+ bind to on the thin filament?

Troponin C (TnC)

What happens when Ca2+ binds to troponin?

Tropomyosin moves, exposing myosin-binding sites on actin

What is the power stroke?

Myosin heads pivot, pulling actin filaments - causes contraction

What does ATP do in muscle contraction?

Binds to myosin, causing cross-bridge detachment