Cardiac Physiology and ECG Quiz

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Questions and Answers

What initiates the prepotential in cardiac conductive cells?

Rapid efflux of calcium ions

Rapid influx of potassium ions

Slow influx of sodium ions (correct)

Sustained influx of chloride ions

What phase is characterized by the influx of calcium ions in cardiac contractile cells?

Repolarization phase

Prepotential phase

Long plateau phase (correct)

Threshold phase

Which part of the ECG represents electrical activation of the ventricles?

PR interval

P wave

T wave

QRS complex (correct)

What does the extended refractory period in cardiac contractile cells allow for?

Complete contraction before another electrical event Signup and view all the answers

Which feature distinguishes cardiac muscle action potentials from skeletal muscle action potentials?

Long plateau phase Signup and view all the answers

What do the segments of an ECG tracing correlate with?

Heart's electrical and mechanical events Signup and view all the answers

What is typically absent in the action potential of cardiac conductive cells?

Resting potential Signup and view all the answers

What characterizes a second-degree partial block in an ECG?

One-half of the P waves are not followed by the QRS complex. Signup and view all the answers

What are the characteristics of the T wave in an ECG?

Repolarization of the ventricles Signup and view all the answers

Which ECG abnormality is indicated by an abnormal electrical pattern prior to the QRS complex?

Atrial fibrillation Signup and view all the answers

In ventricular fibrillation, what is a key feature of the ECG?

Absence of normal electrical activity Signup and view all the answers

What does the QRS complex represent in the cardiac cycle?

Depolarization of the ventricles Signup and view all the answers

What phase follows atrial systole in the cardiac cycle?

Ventricular systole Signup and view all the answers

What is a murmur in the context of heart sounds?

An unusual sound caused by turbulent blood flow Signup and view all the answers

How are heart murmurs graded?

On a scale of 1 to 6 Signup and view all the answers

What occurs during ventricular diastole in the cardiac cycle?

Ventricles are relaxed. Signup and view all the answers

What is the primary function of the pericardium?

To separate the heart from other mediastinal structures Signup and view all the answers

Which structure of the heart is located at the level of the third costal cartilage?

Base Signup and view all the answers

Where is the cardiac notch located?

In the left lung Signup and view all the answers

Which part of the heart lies just to the left of the sternum?

Apex Signup and view all the answers

What is the proper hand positioning for performing CPR?

Between T4 and T9 vertebrae Signup and view all the answers

Which surface of the heart is considered the dorsal surface?

The surface lying near the vertebrae Signup and view all the answers

What distinguishes the orientation of the right and left sides of the heart?

The right side is deflected anteriorly Signup and view all the answers

What does the space known as the pericardial cavity contain?

Pericardial fluid Signup and view all the answers

What determines the thickness of a chamber wall in the heart?

The amount of high-pressure work it does Signup and view all the answers

Why are the walls of the left ventricles the thickest in the heart?

They pump blood against the resistance of the systemic circulation Signup and view all the answers

What is the main function of the heart valves?

To ensure unidirectional blood flow through the heart Signup and view all the answers

How many flaps does the tricuspid valve consist of?

Three flaps Signup and view all the answers

What causes the pulmonary valve to close?

Flow of blood back into the ventricle from the pulmonary trunk Signup and view all the answers

What is another name for the mitral valve?

Bicuspid valve Signup and view all the answers

What is unique about the pulmonary valve compared to the atrioventricular valves?

It has no papillary muscles or chordae tendineae Signup and view all the answers

Where is the mitral valve located?

Between the left atrium and the left ventricle Signup and view all the answers

What is the role of intercalated discs in cardiac muscle cells?

They connect cardiac muscle cells and consist of desmosomes and gap junctions. Signup and view all the answers

What is the primary pacemaker of the heart?

Sinoatrial node Signup and view all the answers

Which characteristic refers to the ability of cardiac cells to transmit an electrical impulse to another cell?

Conductivity Signup and view all the answers

What happens at the atrioventricular (AV) node during the conduction cycle of the heart?

There is a delay of approximately 100 ms. Signup and view all the answers

What is the normal firing rate of the sinoatrial (SA) node?

60 to 100 beats/minute Signup and view all the answers

What are Purkinje fibers primarily responsible for?

Conducting impulses through the ventricles. Signup and view all the answers

Which characteristic of cardiac cells involves the ability to spontaneously initiate an impulse?

Automaticity Signup and view all the answers

What component of the heart conduction system allows the impulse to travel to the right papillary muscle?

Moderator band Signup and view all the answers

Study Notes

Membrane Potentials in Cardiac Conductive Cells

The action potential at the sinoatrial (SA) node features prepotential due to slow sodium ion influx.
Rapid depolarization and repolarization follow the threshold reaching.
Cardiac conductive cells lack a resting potential, allowing spontaneous depolarization.

Membrane Potentials in Cardiac Contractile Cells

Action potential in cardiac contractile cells includes a long plateau phase resulting from calcium ion influx.
This extended refractory period prevents premature contractions.
Comparison of heart muscle to skeletal muscle illustrates distinct action potential shapes.

Electrocardiogram (ECG)

Standard 12-lead ECG uses six chest electrodes and four limb electrodes.
Normal ECG tracing shows P wave, QRS complex, and T wave, depicting the electrical activity of heart contractions.
Each segment in the ECG corresponds to specific events in the cardiac cycle, highlighting mechanical actions.

ECG Abnormalities

Second-degree block shows half of P waves not followed by corresponding QRS complexes.
Atrial fibrillation features an abnormal electrical pattern and increased frequency of QRS complexes.
Ventricular tachycardia displays abnormal QRS complex shape, while ventricular fibrillation results in no coherent electrical activity.
Third-degree block lacks correlation between atrial and ventricular activities, marked by disconnected P waves and QRS complexes.

The Cardiac Cycle

The cardiac cycle includes phases: atrial systole, ventricular systole, atrial diastole, and ventricular diastole.
Atrial contraction occurs during P wave, followed by ventricular contraction during QRS complex, with relaxation starting at the T wave.

Heart Sounds

Heart sounds are correlated with the cardiac cycle and can indicate abnormalities, such as murmurs caused by turbulent blood flow.
Murmurs are graded from 1 to 6, with higher grades indicating more severe disruptions.

Location of the Heart

The heart is situated in the thoracic cavity, between the lungs in the mediastinum, and is enveloped by the pericardium.
The base of the heart aligns with the third costal cartilage, and the apex is positioned near the fourth and fifth ribs.
The cardiac notch indicates the heart's slight leftward deviation affecting the left lung.

CPR Techniques

CPR maintains blood circulation when the heart stops, applying pressure to the sternum to expel blood.
Proper hand placement should be between T4 and T9 levels in the chest.

Heart Valves and Function

Right atrioventricular (tricuspid) valve has three flaps controlled by chordae tendineae and papillary muscles.
Pulmonary semilunar valve prevents backflow from the pulmonary trunk, closing when the ventricle relaxes.
Mitral (bicuspid) valve consists of two cusps attached to chordae tendineae linked to the left ventricle’s papillary muscles.

Conduction System of the Heart

The SA node, AV node, and Purkinje fibers coordinate heart electrical activity, ensuring proper sequence and timing of contractions.
Action potentials originate at the SA node, spreading through atria to AV node with a delay allowing complete atrial blood pumping before ventricles contract.

Pacemakers of the Heart

SA node functions as the primary pacemaker with a firing rate of 60-100 beats/min.
AV node and Purkinje fibers serve as secondary pacemakers, firing at lower rates of 40-60 and 20-40 beats/min respectively.

Characteristics of Cardiac Cells

Automaticity: Ability to initiate impulses autonomously by pacemaker cells.
Excitability: Responsiveness to electrical stimuli, influenced by ion shifts.
Conductivity: Capability to transmit electrical impulses between cardiac cells.
Contractility: Ability to contract following an electrical stimulus.

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Description

Test your knowledge on membrane potentials in cardiac conductive and contractile cells, as well as the interpretation of electrocardiograms (ECG). This quiz covers the action potentials, the electrical events during heart contractions, and common abnormalities in ECG readings. Perfect for students of cardiac physiology!