Cross Section of Heart Cardiac Heart Potential and Electrocardiography

The study of electrical signals in the heart muscles is Electrocardiography (ECG). The potentials generated in the fibers of heart muscles produces ECG waveforms. ECG deals with depolarization and repolarization of heart muscles. ECG signals get generated due to contraction of atria and ventricles. An electrocardiograph is the recorded ECG signal that appears on the … Read more

ECG Recording Setup

ECG Waveform Depolarisation When electrical activity occurs, heart muscle fibers are contracted and produces a movement. This condition is refered as Depolarisation. When blood is pumped around the body, it results in contraction. When chambers are contarcted, it is called systolic. Repolarisation The realxation of heart muscles are called electrical repolarisation. Relaxed heart chambers are … Read more

Electroencephalography | EEG

The recording and study of electrical activity of the brain is Electroencephalography. To record the signals, the electrodes (needle electrodes) are attached on the skull of the patient. Neural depolarization occurs in brain due to stimuli from five senses and thought process. Brain waves are the summations of this neural depolarization. The voltage level on … Read more


Recording of electrical signals from eye is electroretinography. Since retina is extension of the cerebral cortex, it has special relationship with the brain. Due to the exposed position of eye, it is easy to record the potentials. The voltage value of cornea is 20mV positive when compared to eye fundus. Fundus is located behind the … Read more


The recording of electrical activity from muscles is called electromyography. It helps to determine whether the muscles contract or other. The depolarization of muscles causes muscular contractions. Recording the action potential of peripheral nerve is known as Electro neurography. Two types of electrodes are used for recording EMG. Surface electrodes are used when signals are … Read more

ECG Lead System Configuration

The electrical signals from the heart are measured with surface electrodes. The resulting electrode potential in the heart conducts to the body surface. Standardized electrode positions are used to record the ECG. The three types of electrode systems are Bipolar limb leads or standard leads Augmented unipolar limb leads Chest leads Bipolar Limb leads – … Read more

EEG Measurement

EEG Lead System International Federation of EEG society has suggested 10 – 20 electrode placement system for EEG recording. Silver / silver chloride electrodes are used as surface electrodes in this setup. On the scalp, distances between two electrodes are given as 10% and 20% of the distance between specified points. Nasion and Inion are … Read more