The Conduction System & Electrophysiology of the Heart

Flashcards based on lecture notes about the Conduction System & Electrophysiology of the Heart.

Autorhythmic cells

Cardiac muscle cells that control and coordinate the heartbeat.

Contractile cells

Cardiac myocytes where action potentials produce muscle contractions to propel blood.

Sinoatrial (SA) node

Pacemaker cells in the posterior wall of the right atrium; primary pacemaker of the heart.

Atrioventricular (AV) node

Pacemaker cells at the junction between the atria and ventricles.

Internodal pathways

Conducting cells in the atrial walls.

Atrioventricular (AV) bundle

Conducting cells in the ventricles.

Bundle branches

Conducting cells in the ventricles.

Purkinje fibers

Conducting cells in the ventricles.

Pacemaker potential

Gradual depolarization of pacemaker cells due to slow inflow of sodium ions.

Sinus rhythm

Basic heart rhythm established by the SA node.

SA node function

Generates an action potential (electrical impulse).

AV node delay

Allows the atria to contract before ventricular contraction begins.

Electrocardiogram (ECG or EKG)

A recording of the electrical events in the heart.

P wave

Depolarization of the atria.

QRS complex

Depolarization of the ventricles.

T wave

Repolarization of the ventricles.

PQ or PR segment

Conduction through AV node and AV bundle.

ST segment

Flat section after QRS complex.

Normal resting heart rate

60-100 beats/min.

Tachycardia

Faster than normal heart rate.

Bradycardia

Slower than normal heart rate.

Cardiac contractile cells

Form the bulk of the atrial and ventricular walls; branching striated cells with a single nucleus.

Intercalated discs

Interconnect cardiac contractile cells; hold membranes and transfer force of contraction.

Desmosomes

Hold membranes of adjacent cells and transfer the force of contraction.

Gap junctions

Propagate action potentials.

Refractory period

Long in cardiac muscle, prevents summation and tetanus.

Heartbeat

A single cardiac contraction made possible by electrical events.

Action potential in cardiac myocytes

Produces muscle contractions to propel blood.

Membrane potential of pacemaker cells

Unstable, allows them to depolarize spontaneously.

SA node firing rate

60–100 action potentials per minute.

AV node firing rate

40–60 action potentials per minute.

Dominant pacemaker

SA node, due to its faster firing rate.

Internodal pathways function

Spread the stimulus from the SA node to the AV node.

AV bundle function

Transmits impulse to the left and right bundle branches.

Purkinje fibers function

Spread impulse to the contractile cells of the ventricles.

Ventricular contraction

Begins at the apex and spreads towards the base.

Electrical activity spread

Into the tissues around the heart, detected by ECG.

ECG use

To diagnose heart disease.

Atrial contraction

Occurs after the P wave.

Ventricular contraction

Begins shortly after the R wave peak.

Waves on ECG

Appear as deflections above or below the baseline.

Segments on ECG

Flat sections of the baseline between two waves.

Intervals on ECG

Combinations of waves and segments.

R-R interval use

To time heart rate.

PP interval use

To time heart rate.

Action potential length in ventricular contractile cell

30 times longer than in skeletal muscle fiber.

Cardiac muscle cells characteristics

Branching striated cells with a single nucleus.

Pacemaker cells

Initiate and distribute electrical impulses that stimulate contraction.

Conduction system

Consists of pacemaker and conducting cells.

Unstable resting potential

Allows pacemaker cells to depolarize spontaneously.

Electrical events

Make heartbeat possible.

Q wave

First negative deflection of the QRS complex.

S wave

Negative deflection following the R wave.

Function of contractile cells

Produce muscle contraction.

Function of autorhythmic cells

Control and coordinate the heartbeat.

Location of conducting cells

Internodal pathways & ventricles.

SA node

Primary Pacemaker.

Purkinje fibers

Fast conducting fibers in ventricles.

P wave

Atrial Depolarization.

QRS Complex

Ventricular Depolarization.

T Wave

Ventricular Repolarization.

PR Segment

AV Node Conduction.

QT Interval

Ventricular Activation to Recovery.

ST Segment

Early Ventricular Repolarization.

Heart Rate

Beats per Minute.

SA Node Rate

60-100 bpm.

AV Node Rate

40-60 bpm.

Ventricular Rate

20-40 bpm.

Intercalated Discs

Connect Cardiac Cells.

Gap Junctions

Electrical Communication.

Desmosomes

Structural Support.

Myocytes

Cardiac Muscle Cells.

Action Potential

Electrical Signal.

Depolarization

Electrical Activation.

Repolarization

Electrical Recovery.

Voltage Gated Channels

Ion Passage.

Autorhythmicity

Self-Excitation.

Cardiac Cycle

Heartbeat Sequence.

Cardiac Output

Blood Volume per minute.

Arrhythmia

Abnormal Rhythm.

Fibrillation

Uncoordinated Contraction.

Heart Block

Conduction Disruption.

Ectopic Focus

Abnormal Pacemaker.

Ischemia

Reduced Blood Flow.

Infarction

Tissue Death.

Apex

Pointed Part of Heart.

Base

Top Part of Heart.

Atria

Receiving Chambers.

Ventricles

Pumping Chambers.

Septum

Wall Separating Sides.

Valves

Prevent Backflow.

Cardiac Conduction System

Pathway of Electrical Signals in Heart.

Sinoatrial Node

Cardiac Pacemaker

Atrioventricular Valve

Heart Valve between Atria and Ventricles

Aortic Valve

Heart Valve between Left Ventricle and Aorta

Pulmonic Valve

Heart Valve between Right Ventricle and Pulmonary Artery

Bicuspid Valve

Heart Valve between Left Atrium and Left Ventricle

Cardiac Muscle

Heart Muscle

Coronary Artery

Artery Supplying Oxygenated Blood

Tricuspid valve

Heart Valve between Right Atrium and Right Ventricle