Cardiac Physiology 2: ECG and Limb Leads
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Questions and Answers

What does the P wave on an ECG represent?

  • Atrial repolarization
  • Atrial depolarization (correct)
  • Ventricular depolarization
  • Ventricular repolarization

Which component of the ECG is associated with ventricular contraction?

  • QRS complex (correct)
  • P wave
  • PR interval
  • T wave

What is the function of the AV nodal delay represented in the ECG?

  • Preventing atrial contraction
  • Limiting blood flow to the aorta
  • Speeding up heart rate
  • Allowing time for ventricular filling (correct)

Tachycardia is characterized by which of the following?

<p>Fast heart rate (C)</p> Signup and view all the answers

Which of the following does NOT contribute to the formation of the ECG?

<p>Direct recording of heart's electrical activity (A)</p> Signup and view all the answers

What cardiac event does the T wave on an ECG indicate?

<p>Ventricular repolarization (A)</p> Signup and view all the answers

Which ECG abnormality is characterized by an irregular heart rhythm?

<p>Ventricular fibrillation (A)</p> Signup and view all the answers

During diastole, how does the heart fill with blood?

<p>Through passive ventricular filling (A)</p> Signup and view all the answers

What occurs during diastole's active filling phase?

<p>The atria contract. (D)</p> Signup and view all the answers

What initiates the period of isovolumic contraction?

<p>Closure of the AV valves. (B)</p> Signup and view all the answers

Which valves are closed during the period of ejection in systole?

<p>AV valves only. (B)</p> Signup and view all the answers

During which phase do the semilunar valves close?

<p>Isovolumic relaxation. (A)</p> Signup and view all the answers

What is the primary characteristic of laminar flow during passive ventricular filling?

<p>Occurs quietly without generating sound. (C)</p> Signup and view all the answers

What happens to the AV valves during the phase of isovolumic contraction?

<p>They close. (D)</p> Signup and view all the answers

Which phase follows the period of ejection?

<p>Isovolumic relaxation. (C)</p> Signup and view all the answers

What is the state of the semilunar valves during ventricular filling?

<p>They are closed to prevent backflow. (B)</p> Signup and view all the answers

What happens to the AV valves at the onset of ventricular systole?

<p>AV valves close to prevent backflow (D)</p> Signup and view all the answers

What occurs during passive ventricular filling?

<p>Blood flows smoothly without sound (C)</p> Signup and view all the answers

What is the state of the semilunar valves during isovolumic relaxation?

<p>Semilunar valves close after blood return (A)</p> Signup and view all the answers

During which phase do the AV valves open to allow ventricular filling?

<p>Diastole (A)</p> Signup and view all the answers

What primarily causes the closing of the semilunar valves during diastole?

<p>Blood flowing back toward the ventricles (C)</p> Signup and view all the answers

What is the effect of ventricular contraction on the AV valves?

<p>They close to prevent reflux (B)</p> Signup and view all the answers

Which processes primarily take place during active ventricular filling?

<p>Atrial contraction completes the filling (C)</p> Signup and view all the answers

Which of the following best describes the ECG?

<p>A record of cardiac impulses reaching the body surface. (A)</p> Signup and view all the answers

What does the QRS complex primarily represent in the ECG?

<p>Ventricular depolarization (A)</p> Signup and view all the answers

Which ECG abnormality is characterized by a fast heart rate?

<p>Tachycardia (D)</p> Signup and view all the answers

In the context of ECG, what does the P wave indicate?

<p>Atrial depolarization (A)</p> Signup and view all the answers

Which component of the cardiac cycle occurs after ventricular contraction?

<p>Diastole (B)</p> Signup and view all the answers

Which of the following leads is used to represent the difference between the left arm and the left leg?

<p>Lead III (B)</p> Signup and view all the answers

What is the main significance of the ST segment in an ECG?

<p>It indicates the period of ventricular relaxation. (C)</p> Signup and view all the answers

What occurs during the diastolic phase of the cardiac cycle?

<p>Passive ventricular filling. (D)</p> Signup and view all the answers

Flashcards

What does an ECG record?

An ECG doesn't directly record electrical activity in the heart; it measures the impulses that reach the body surface.

What does the ECG show?

The ECG shows changes in voltage detected between two points on the skin, not the actual electrical potential in the heart.

What does the P wave represent?

The P wave on an ECG represents the electrical signal that starts the contraction of the atria.

What does the QRS complex represent?

The QRS complex on an ECG represents the electrical signals that trigger the contraction of the ventricles.

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What does the T wave represent?

The T wave on an ECG represents the electrical signal that indicates the ventricles are relaxing after contraction.

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What is tachycardia?

An irregular heart rhythm, meaning the heart beats too fast.

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What is an extrasystole (premature beat)?

An extra heartbeat that occurs before the next expected beat.

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What is a complete heart block?

The heart's electrical signal doesn't reach the ventricles properly, causing a slow or irregular heartbeat.

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Diastole

Phase of the heart cycle where ventricles relax and fill with blood. This period is divided into passive and active filling phases.

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Systole

Phase of the heart cycle where ventricles contract and pump blood out.

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Passive Ventricular Filling

The period during diastole when blood flows passively into relaxed ventricles. This flow is silent.

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Active Ventricular Filling

The part of diastole when the atria contract, completing ventricular filling. This flow is also silent.

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Atrioventricular (AV) Valves

Initially closed during diastole and remain closed during the beginning of ventricular systole. These valves prevent backflow of blood from ventricles to atria.

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Semilunar Valves

Initially closed during diastole and open during ventricular systole. These valves control the flow of blood from the ventricles to the arteries.

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Isovolumic Contraction

The brief moment at the beginning of systole where the ventricles contract, causing AV valves to close. No blood is ejected during this phase.

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Ejection Phase

The period during systole where continued ventricular contraction pushes blood out of the ventricles and into the arteries causing semilunar valves to open.

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Isovolumic Relaxation

The brief moment at the beginning of diastole where blood flowing back toward the ventricles causes the semilunar valves to close, signaling the beginning of ventricular diastole.

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What does ECG show?

The ECG shows the difference in voltage between two electrodes placed on the skin.

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What is an extrasystole?

The term for the ECG abnormality where an extra heart beat occurs ahead of the next expected beat.

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Study Notes

Cardiac Physiology 2

  • Electrocardiogram (ECG): Records the electrical impulses that reach the body surface during cardiac activity, not a direct recording of the heart's electrical activity.
  • ECG shows the overall cardiac activity during depolarization and repolarization.
  • The recording is the comparison of voltages detected by electrodes on the skin, not actual potentials.
  • ECG waves correlate to specific cardiac events:
    • P wave: Represents atrial depolarization.
    • QRS complex: Represents ventricular depolarization.
    • T wave: Represents ventricular repolarization.

Limb Leads

  • ECG uses electrodes placed on different parts of the body to measure the electrical activity.
  • Limb leads measure the electrical potential differences between limbs (arms and legs).
    • Lead I: Right arm to left arm
    • aVR: Right arm
    • aVL: Left arm
    • Lead II: Right arm to left leg
    • aVF: Left leg
    • Lead III: Left arm to left leg
  • A ground electrode is also used.

Chest Leads

  • Chest leads (V1-V6) are placed on the chest wall to measure the electrical activity.
  • The placement locations are numbered as seen in the diagrams.

Cardiac Arrhythmias

  • Tachycardia: A rapid heart rate.
  • Extrasystole (premature beat): An extra heartbeat that occurs before the next normal heartbeat.
  • Ventricular fibrillation: Disorganized electrical activity in the ventricles.
  • Complete heart block: A condition where the electrical signals from the atria do not reach the ventricles.

Cardiac Myopathies

  • Myocardial infarction: A heart attack, where blood flow to the heart muscle is blocked. 
    • Characterized by specific ECG patterns.

Cardiac Cycle

  • Diastole: The period of relaxation of the heart chambers, divided into different phases (Passive ventricular filling, and Active ventricular filling).
    • During Diastole, the AV valves open, allowing blood to passively fill the ventricles.

    • During Active ventricular filling, the AV valves remain closed and the atria contract to complete ventricular filling.

  • Systole: The period of contraction of the heart chambers, which can be further divided into:
    • Isovolumetric contraction: Ventricular contraction causes the AV valves to close, beginning ventricular systole. The semilunar valves remain closed during this period.
    • Period of ejection: Continued ventricular contraction pushes blood out of the ventricles, causing the semilunar valves to open.
    • Isovolumetric relaxation: Blood flowing back toward the relaxing ventricles closes the semilunar valves, marking the start of ventricular diastole. The AV valves also close during this period.

Heart Sounds

  • Heart sounds are produced by the turbulent flow of blood through the heart valves.
  • The first heart sound (S1) is caused by the closure of the AV valves.
  • The second heart sound (S2) is caused by the closure of the semilunar valves.
  • There are instances where no audible sound is produced during the various phases of the cardiac cycle.

Heart Valve Disorders and Murmurs

  • Murmurs are abnormal heart sounds caused by turbulent blood flow through damaged or narrowed heart valves. 
  • Murmur patterns and timings with stethoscope correlate to heart valve disorders.
  • Different types of murmurs (e.g., systolic, diastolic) and associated valve defects (stenotic, insufficient) are linked to specific murmur characteristics.

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Description

Explore the nuances of cardiac physiology with a focus on the Electrocardiogram (ECG) and limb leads. This quiz covers the basics of how ECG records electrical impulses during cardiac activity and correlates various ECG waves to specific cardiac events. Understand the placement of limb leads and their significance in measuring electrical activity.

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