the heart

Question 1

electricity of the heart

Answer 1

Membrane potential Action potential
Specialised conducting system Excitation-contraction coupling

Question 2

membrane potential

Answer 2

Determined by ion* concentration inside vs. outside the cell
*protons (+) ≠ electrons (-) i.e. charged molecule

Na+ and Ca2+ currents = (+) inwards = depolarising

K+ currents = (+) outwards = repolarising

Question 3

action potential

Answer 3

sequential activation and inactivation of inward (Na+ and Ca2+) and outward (K+) currents

Question 4

action potentail stages

Answer 4

upstroke- Opening of voltage- gated Na+ channels allows inward Na+ (INa)

notch- Rapid Vm-dependent inactivation of INa
Activation of outward K+ (Ito)

plateau- Balance of inward Ca2+ and outward K+

repolarisation- Inward currents are inactivated and outward K+ (IK) predominate

resting

Question 5

cardiac cycle

Answer 5

1) Atrial systole begins:
Atrial contraction forces a small amount of additional blood into relaxed ventricles.

2) Atrial systole ends, atrial diastole begins

3) (Isovolumetric contraction)
a Ventricular systole first phase: Ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves.

4) Ventricular systole-second phase: As ventricular pressure rises and exceeds pressure
In the arteries, the semilunar valves open and blood Is ejected.

5) (isovolumetric relaxation)
Ventricular diastole early:
As ventricies relax, pressure in ventricles drops; blood flows back against cusps of semilunar valves and forces them closed. Blood flows into the relaxed atria.

6)Ventricular diastole late:
All chambers are relaxed.
Ventricles fill passively.

Question 6

cardiac haemodynamics

Answer 6

Cardiac output = Stroke volume x heart rate CO = SV x HR
(e.g. 5.3 litres = 75 ml x 70 bpm)

Blood pressure = cardiac output x peripheral vascular
resistance
BP = CO x PVR

Question 7

coronary arteries

Answer 7

RIGHT
- right coronary artery
-posterior descending artery
-right marginal artery

LEFT
- left coronary artery
-left circumflex artery
- left marginal artery
- left anterior descending artery
- diagonal branch

Question 8

what flow do coronary arteries have

Answer 8

Coronary arterial flow is diastolic

Question 9

heart conditions

Answer 9

Mechanics i.e. the pump
cardiomyopathy
valvular disease

Electricity i.e. the trigger
arrhythmias
conducting system disease

Plumbing i.e. the blood supply
- coronary heart disease