This document provides an overview of the basics of electrophysiology of the heart. It discusses key concepts such as resting membrane potential, graded potentials, depolarization, action potentials, repolarization, and refractory periods. The document explains that electrical activity exists in all organs due to ion transport across cell membranes and is predominant in muscles like the heart. It describes the conduction pathway in the heart from the sinoatrial node to the ventricles. Finally, the five phases of the cardiac action potential are outlined involving the movement of sodium, calcium, and potassium ions across cell membranes.

1. Basics of
Electro Physiology of Heart
GUIDANCE TO PHARMACY
STUDENTS
Prof. Dr. Sutharson Lingadurai

2. Importance of Understanding Basics
of Electrophysiology
• Basics of Electrophysiology are same for All
muscles and neurons
• Electrophysiology is the basic principle in the
formation of ECG of Heart
• Most of the antiarrhythmic drugs acting on
Ion channels of heart and increases Action
potential duration and the Effective refractory
period (ERP)

3. Electro Physiology
Electro Physiology deals with study of
Electrical activity existing in tissue/organ
Electrical activity is existing in all part of our
Organs
But its activity is predominant in muscles,
especially in auto rhythmic fibers of Heart

4. Basis of Electrical activity
• Ion Transport/Conduction across cell
membranes
• Na+,K+,Ca2+ are the prominent ions play role in
myocardial tissues are concern

7. Basic Terms in Electro Physiology
Resting Membrane Potential: The relatively
static membrane potential of quiescent cells
is called the resting membrane potential (or
resting voltage)
Graded Potential : Graded potentials are
temporary changes in the membrane voltage,
the characteristics of which depend on the
size of the stimulus Threshold

8. Depolarization: It is a positive change from
the resting potential achieved by increased
permeability to an ion (Mainly by Na+ Influx)
leads to attainment of peak membrane
potential (Action Potential)
Action Potential : sudden, fast, transitory, and
propagating change of the resting
membrane potential due to depolarization

9. Repolarization: is the return of the ions to
their previous resting state (Closing of
Na+Channel and openeing of K+Channel)
Hyperpolarization: is a change in a cell's
membrane potential that makes it more
negative.

10. Absolute Refractory Period (Effective
refractory Period) ERP : Additional stimulus
cannot create new Action Potential
Relative Refractory period: During which
strong stimuli may trigger anew action
potential

11. Conduction Pathway in Heart
SA Node
AV Node
Bundle
of His
Purkinje
fibers
Ventricles

13. SA Node

14. Phases of Electrophysiology of Heart
• Phase 0 (Depolarization): Upon stimulation
Na+Channel opens Na+Influx cells become positively
charged 20mV
• Phase 1: (Early Repolarization) : K+ Channel opens,
brief efflux of Potassium
• Phase 2 :( Plateau phase) Ca2+channel opens and influx
of Ca2+ions happens
• Phase 3: (Repolarization phase) Ca2+channel closes
and K+ Channel opens efflux of Potassium
• Phase 4: (Resting Phase) only K+ Channel opens efflux
of Potassium establish a negative resting membrane
potential -90mV