Heart's Electrical Conduction System Quiz

Electrical Conduction System

• The electrical conduction system of the heart consists of:
  • SA (Sinoatrial) node: the natural pacemaker, located in the right atrium
  • AV (Atrioventricular) node: located between the atria and ventricles
  • Bundle of His: a group of specialized fibers that transmit the electrical signal from the AV node to the ventricles
  • Purkinje fibers: a network of fibers that transmit the electrical signal to the ventricular myocardium

ECG Waves

• The ECG waveform consists of:
  • P wave: represents atrial depolarization
  • PR interval: the time between the P wave and the QRS complex, representing the delay between atrial and ventricular depolarization
  • QRS complex: represents ventricular depolarization
  • ST segment: the period of ventricular contraction
  • T wave: represents ventricular repolarization
  • U wave: a small deflection that can occur after the T wave, representing the repolarization of the Purkinje fibers

ECG Intervals

• The ECG intervals are:
  • PR interval: 120-200 ms (0.12-0.20 seconds)
  • QRS duration: 80-120 ms (0.08-0.12 seconds)
  • QT interval: 350-450 ms (0.35-0.45 seconds)
  • RR interval: the time between two consecutive R waves, representing the heart rate

ECG Axes

• The ECG axes are:
  • Lead I: records the difference in potential between the left and right arms
  • Lead II: records the difference in potential between the left leg and the right arm
  • Lead III: records the difference in potential between the left leg and the left arm
  • aVR: records the difference in potential between the right arm and the center of the heart
  • aVL: records the difference in potential between the left arm and the center of the heart
  • aVF: records the difference in potential between the left leg and the center of the heart

Electrical Conduction System

• SA (Sinoatrial) node is the natural pacemaker, located in the right atrium.
• AV (Atrioventricular) node is located between the atria and ventricles.
• Bundle of His is a group of specialized fibers that transmit the electrical signal from the AV node to the ventricles.
• Purkinje fibers are a network of fibers that transmit the electrical signal to the ventricular myocardium.

ECG Waves

• P wave represents atrial depolarization.
• PR interval is the time between the P wave and the QRS complex, representing the delay between atrial and ventricular depolarization.
• QRS complex represents ventricular depolarization.
• ST segment is the period of ventricular contraction.
• T wave represents ventricular repolarization.
• U wave is a small deflection that can occur after the T wave, representing the repolarization of the Purkinje fibers.

ECG Intervals

• PR interval is 120-200 ms (0.12-0.20 seconds).
• QRS duration is 80-120 ms (0.08-0.12 seconds).
• QT interval is 350-450 ms (0.35-0.45 seconds).
• RR interval is the time between two consecutive R waves, representing the heart rate.

ECG Axes

• Lead I records the difference in potential between the left and right arms.
• Lead II records the difference in potential between the left leg and the right arm.
• Lead III records the difference in potential between the left leg and the left arm.
• aVR records the difference in potential between the right arm and the center of the heart.
• aVL records the difference in potential between the left arm and the center of the heart.
• aVF records the difference in potential between the left leg and the center of the heart.

ECG in Physiology Lab

Introduction

• ECG is a non-invasive test that records the electrical activity of the heart.
• ECG is used in physiology labs to measure heart electrical activity and diagnose cardiac arrhythmias.

Lead Placement

• Standard 12-lead ECG configuration is used in physiology labs.
• Lead placement locations:
  • RA (right arm): right wrist
  • LA (left arm): left wrist
  • RL (right leg): right ankle
  • LL (left leg): left ankle
  • V1-V6: chest leads, placed on the chest

ECG Components

• P wave: represents atrial depolarization
• PR interval: time between P wave and QRS complex
• QRS complex: represents ventricular depolarization
• ST segment: represents ventricular repolarization
• T wave: represents ventricular repolarization
• QT interval: time between QRS complex and T wave

ECG Analysis

• Heart rate: calculated from the time between QRS complexes
• Rhythm: regular or irregular
• Axis: direction of the heart's electrical activity
• P wave morphology: shape and size of the P wave
• QRS complex morphology: shape and size of the QRS complex

Normal ECG Values

• Heart rate: 60-100 beats per minute
• PR interval: 120-200 milliseconds
• QRS duration: 80-120 milliseconds
• QT interval: 300-450 milliseconds

Common ECG Abnormalities

• Arrhythmias: irregular heart rhythms
• Tachycardia: heart rate > 100 beats per minute
• Bradycardia: heart rate < 60 beats per minute
• Long QT syndrome: prolonged QT interval

ECG Applications

• Cardiovascular disease diagnosis
• Monitoring of cardiac arrhythmias
• Evaluation of cardiac function