CARDIO- Cardiac action potentials and conduction pathway

Question 1

where are pacemaker potentials generated

Answer 1

SAN

Question 2

how does the SAN produce pacemaker potential

Answer 2

phase 4- resting membrane potential = -60mV
If channels are hyperpolarisation activated sodium channels - sodium influx - threshold

phase 0- voltage gated calcium channels - allow calcium influx - allows for depolarisation

phase 3- voltage gated potassium channels- potassium efflux- repolarisation

Question 3

outline the conduction of electrical activity from the SAN through the heart

Answer 3

SAN - conduction to both atria to AVN
AVN slows electrical conduction between atria and ventricles (allowing for ventricles to fill correctly)
electrical impulse travels to bundle of His
bundle of His to purkinje fibres = quick - allows both ventricles to be stimulated and contracted together

Question 4

how are atria/ventricular action potentials generated

Answer 4

phase 4 - RMP- -90mv
phase 0 - rapid depolarisation - voltage gated sodium channels - open causing depolarisation
phase 1 - rapid depolarisation continued
phase 2 - plateau phase - longest phase - unable to fire more impulses - VGNaC inactivated - essential for proper blood ejection form the heart - VGCaC open allowing calcium reflux
phase 3- VGCaC switch off and potassium channels switch on allowing repolarisation through K+ efflux

Question 5

outline the conduction pathway relating to an ECG

Answer 5

P - atrial depolarisation
QRS- ventricle depolarisation
ST interval - between ventricle depolarisation and repolarisation
T- ventricle repolarisation