PSL301H1 Lecture 8: L8 Cardiac Excitability (HR & ECG)

• School: UTSG
• Department: Physiology
• Course: PSL301H1
• Professor: Michelle French

Document Summary

Lecture 8 cardiac excitability: heart rate and ecg. There are two general types of cardiac action potentials: non-pacemaker cell (myocyte) action potentials (cid:862)fast response(cid:863) action potentials rapid depolarization, muscle cells (cid:862)soldiers(cid:863) - that need instructions to fire. E(cid:448)erythi(cid:374)g (cid:449)e"(cid:448)e dis(cid:272)ussed so far is this (cid:373)yo(cid:272)yte. Sits at resting potential until it receives a stimulus to react: pacemaker (autorhythmic) cells generate spontaneous action potentials (cid:862) lo(cid:449) respo(cid:374)se(cid:863) a(cid:272)tio(cid:374) pote(cid:374)tials slow rate of depolarization. Spontaneous generation of action potential via autorhythmic cells. The threshold for ap generation is the threshold for vgcc activation and (dotted line) and the cell normally polarizes to around -60mv. Slow climb is particular to the autorhythmic cell capacity to slowly depolarize until you reach the threshold for ca and then you get the second action potential. Area between action potential is called the pacemaker potential shape determines the heart rate. Electrical i(cid:374)itiator cells, (cid:858)pace(cid:373)akers(cid:859), are the u(cid:374)derlyi(cid:374)g reaso(cid:374) that hearts spontaneously contract.