Figure 161

Transmembrane action potential of a Purkinje fiber as recorded with an intracellular microelec-trode. When the electrode tip penetrates the fiber, a resting membrane potential of -90 mV is recorded. The application of a subthreshold stimulus (#1) produces a depolarizing current that fails to result in excitation of the myocardial cell. The application of a threshold stimulus (#2) reaches the threshold potential (TP) and results in an inward current and an action potential. Major transmembrane currents carried by specific ions entering the cell through selective ion channels are depicted to the right. Antiarrhythmic agents alter the electrophysiologic properties of the cardiac cells by modulating one or more of the transmembrane currents, especially the fast inward sodium current and the transmembrane currents carried by the potassium ion (IK and IK-ATP). I na — fast inward sodium current; Ica — "L"-type calcium current; Ito — transient outward current; INa-Ca — sodium-calcium exchange current; IK-ATP — adenosine triphosphate-sensitive potassium current; IK — inward rectifying potassium current; IK — delayed rectifying potassium current.

200 Time (msec)

Was this article helpful?

0 0
Peripheral Neuropathy Natural Treatment Options

Peripheral Neuropathy Natural Treatment Options

This guide will help millions of people understand this condition so that they can take control of their lives and make informed decisions. The ebook covers information on a vast number of different types of neuropathy. In addition, it will be a useful resource for their families, caregivers, and health care providers.

Get My Free Ebook

Post a comment