ECG Leads Quiz

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Questions and Answers

Which of the following is the correct equation for calculating pressure?

$pressure = velocity \div resistance$

$pressure = force \div area$ (correct)

$pressure = volume \times size$

$pressure = energy \times potential$

What are the units commonly used to measure pressure?

cm Hg or mm of H2O

mm Hg or cm of H2O (correct)

Kilopascal or Torr

Pascal or mm of H2O

Which of the following concepts describes the study of forces that affect the movement of blood?

Hemodynamics (correct)

Coronary circulation

Electrophysiology

Cardiovascular control

Which of the following is true about the parallel arrangement of vascular beds?

It decreases the total resistance in the circuit. Signup and view all the answers

What is the function of the cardiac conduction system?

To control the action potential in cardiac muscles. Signup and view all the answers

Which of the following is true about the cardiac action potential?

It is determined by the interaction between pumps and channels. Signup and view all the answers

What is responsible for the initiation of the cardiac action potential?

Pacemaker potential Signup and view all the answers

Which of the following factors determines impulse conduction in the heart?

All of the above Signup and view all the answers

Which channel type is responsible for fast impulse conduction in the heart?

Sodium channel Signup and view all the answers

Which of the following is a major determinant of the cardiac impulse refractory period?

Potassium channel function Signup and view all the answers

Which of the following is the major effect of the parasympathetic nervous system on heart conduction?

Inhibit cAMP generation Signup and view all the answers

Which of the following is a characteristic of ventricular fibrillation (v-fib)?

V-fib is characterized by uncoordinated pumping of the heart. Signup and view all the answers

Which of the following can cause high ventricular rates in patients with pre-excitation syndrome?

Exercise Signup and view all the answers

Which of the following is a characteristic of 3rd degree AV node block?

There is no communication between the atria and ventricles. Signup and view all the answers

Moving from the supine to the standing position will increase hydrostatic pressure in the feet by

50 mm Hg Signup and view all the answers

When moving from the supine to the standing position, what happens to blood flow through the capillaries in the feet?

Decreased greatly Signup and view all the answers

Which equation represents Ohm's law for blood flow?

$R = \frac{\Delta P}{F(Q)}$ Signup and view all the answers

Which law describes the relationship between flow rate, pressure difference, and vessel radius?

Poiseuille's law Signup and view all the answers

Which of the following leads is a standard bipolar limb lead in an ECG?

aVL Signup and view all the answers

What is the formula to determine the heart rate in beats per minute (BPM) using the R-R interval on an ECG?

Heart Rate (BPM) = 1500 / # of small squares in R-R interval Signup and view all the answers

Which of the following arrhythmias is characterized by an irregular baseline, undiscernable P waves, and irregular R-R intervals?

Atrial fibrillation Signup and view all the answers

Which of the following arrhythmias is characterized by wide QRS complexes and rapid firing of a single ectopic ventricular focus?

Ventricular tachycardia (v-tach) Signup and view all the answers

Which of the following is true about the cardiac pacemakers in the heart?

The SA node is the fastest pacemaker in a normal heart Signup and view all the answers

What is the most effective way to extend the effective refractory period (ERP) in the ventricle?

Potassium channel blockade Signup and view all the answers

Which of the following is true about the autonomic regulation of cardiac electrophysiology?

Parasympathetic stimulation inhibits L-type calcium channels in the SA and AV nodes Signup and view all the answers

Which of the following is true about the impulse initiation (automaticity) in the heart?

Sodium channel opening is responsible for fast action potentials in the Purkinje fibers Signup and view all the answers

Study Notes

Pressure Calculation and Units

Pressure is calculated using the equation: Pressure = Force / Area.
Common units for measuring pressure include Pascals (Pa), mmHg, and atm (atmospheres).

Blood Movement Forces

The study of forces affecting blood movement is known as hemodynamics.

Vascular Beds Arrangement

In a parallel arrangement of vascular beds, each bed receives a fraction of the total blood flow, allowing for independent control of blood distribution.

Cardiac Conduction System

The cardiac conduction system regulates the heart's rhythm by conducting electrical impulses, initiating contractions.

Cardiac Action Potential

The cardiac action potential includes phases of depolarization and repolarization, critical for heartbeats.
Sodium channels facilitate the rapid initiation of the cardiac action potential.

Impulse Conduction Factors

Impulse conduction in the heart is mainly determined by cell membrane properties and the type of ion channels present.

Fast Impulse Conduction

Gap junctions allow for fast impulse conduction due to direct electrical connections between cardiac cells.

Refractory Period Determinants

The refractory period of the cardiac impulse is significantly influenced by potassium ion dynamics.

Parasympathetic Nervous System Effects

The parasympathetic nervous system primarily decreases heart rate by acting on the sinoatrial node.

Ventricular Fibrillation Characteristics

Ventricular fibrillation (v-fib) is characterized by erratic electrical activity in the heart, leading to ineffective pumping and lack of blood flow.

Pre-excitation Syndrome and High Ventricular Rates

High ventricular rates in pre-excitation syndrome can be caused by re-entry circuits due to accessory pathways.

3rd Degree AV Node Block

In 3rd degree AV node block, there is complete dissociation between atrial and ventricular activity, causing a slower ventricular escape rhythm.

Hydrostatic Pressure Changes

Moving from supine to standing position increases hydrostatic pressure in the feet due to gravitational effects.

Blood Flow in Capillaries

When transitioning to a standing position, blood flow through the capillaries in the feet may decrease initially due to pooling of blood while muscles adjust.

Ohm's Law and Blood Flow

Ohm's law for blood flow is represented as: Flow = Pressure Difference / Resistance.

Flow Rate Relationships

The relationship between flow rate, pressure difference, and vessel radius is described by Poiseuille's law.

ECG Standard Leads

A standard bipolar limb lead in an ECG is Lead I, which compares the potential difference between the left arm and right arm.

Heart Rate Calculation

The formula to determine heart rate in beats per minute (BPM) from the R-R interval is: HR = 60 / R-R interval (in seconds).

Arrhythmias Characteristics

Atrial fibrillation is characterized by an irregular baseline and undiscernable P waves, with irregular R-R intervals.
Ventricular tachycardia features wide QRS complexes with rapid firing from a single ectopic ventricular focus.

Cardiac Pacemakers

Cardiac pacemakers, primarily located in the sinoatrial node, are responsible for initiating heartbeats and maintaining the regular rhythm.

Effective Refractory Period Extension

The most effective way to extend the effective refractory period (ERP) in the ventricle is by increasing potassium channel activity.

Autonomic Regulation of Cardiac Electrophysiology

Autonomic regulation plays a critical role in cardiac electrophysiology, influencing heart rate and conduction velocity through sympathetic and parasympathetic effects.

Automaticity Initiation

Impulse initiation (automaticity) in the heart is primarily driven by pacemaker cells in the sinoatrial node.

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Description

Test Your Knowledge of ECG Leads: Identify the Different Bipolar and Unipolar Leads