Phys properties of the heart handout 1 per page

• To describe the ionic basis for the different stages of the membrane potential changes in atrial/ventricular muscle, nodal and conducting tissue throughout the heart.

atrial/ventricular depolarisation

(5 phases) (gNa+ means increased diffusion basically g means more permeability to something so gCa2+ means theres more calcium entering)

phase 0

gNa+ increases as channels open and Na+ rushes into cell causing a rapid depolarisation and reaching action potential threshold

phase 1

gNa+ decreases and Na+ channels close causing repolarisation

phase 2

L-type Ca2+ channels open, (the increase in calcium concentration causes gK+)

phase 3

gK+ increases and K+ channels open (Due to the increasing concentration of Calcium) leading to rapid repolarisation. Ca2+ channels close

phase 4

stable resting membrane potential

gK+ exceeds gNa+ by 50:1