anatomy lab Cardiac conduction system & ECG

Cardiac conduction system

Transmits action potentials throughout the heart to promote coordinated, sequential heart muscle contractions

• Composed of specialized, noncontractile cardiac cells

Depolarization

responsible for travel of action potentials

• Caused by influx of Ca2+ ions, which reverses membrane potential

Action potentials trigger

contractions

Conduction System

● A series of depolarization events throughout the heart

● Conducted through heart via bundles of electrically excitable cells and electrical conduction structures

Sinoatrial node (SA node)

Spreads depolarizing stimulus through both atria

-(impulse cannot pass directly into ventricles due to insulating fibrous skeleton)

Pacemaker of the hear

SA node

(sets rhythm ~75 bpm)

Atrioventricular node (AV node)

Action potential is delayed, ensuring the atria are completely contracted before ventricular contraction begins

AV bundle (bundle of His)

Connects atria to ventricles

Bundle branches (right & left)

Conduct action potential through interventricular septum

Purkinje fibers (subendocardial conducting network)

Conduct action potential through myocardium of ventricles

ECG (electrocardiogram)

Measures the electrical activity of the heart

p wave

atrial depolarization

PR segment

AV nodal delay

QRS complex

ventricular depolarization (atria repolarizing simultaneously)

ST segment

time during which ventricles are contracting and emptying

T wave

ventricular repolarization

TP interval

time during which ventricles are relaxing and filling

Baroreceptors

◦ Respond to changes in blood pressure

Chemoreceptors

◦ Respond to concentration of chemicals (e.g., O2 , CO2 , pH)

Cardioinhibitory center

Stimulated by:

• Increase in BP

• Increase in O2

• Decrease in CO2

• Increase in pH

• slows heart rate

Cardioacceleratory center

Stimulated by:

• Decrease in BP

• Decrease in O2

• Increase in CO2

• Decrease in pH

• accelerates heart rate

what is A?

SA node

what is B?

Atrioventricular node

what is C?

Atrioventricular bundle or bundle of HIS

what is D?

Right and left bundle branches

what is E?

Purkinje fibers (subendocardial conduction network)

what is A?

P wave

what is B?

Q peak

what is C?

R peak

what is D?

S peak

what is E?

T wave

what is F?

QRS complex

The wave of atrial depolarization reaches this structure in the right atrium shortly after the SA node depolarization.

atrioventricular node (AV)

This component contains the cardiac pacemaker cells and has an unstable resting membrane potential causing the node to undergo rhythmic depolarization that spreads throughout the right and left atria

sinoatrial node (SA)

These structures carry the action potential into the two sides of the heart's myocardium.

right and left AV bundle branches

These structures transmit the action potential to the myocardium of the ventricles to cause contraction.

Purkinje fibers

The depolarization spreads down this structure that is located in the interventricular septum

atrioventricular (AV) bundle or Bundle of HIS

Identify the scenarios in which the  the cardioinhibitory (parasympathetic) center would be stimulated

Increase in blood oxygen levels 

Increase in blood pH 

Decrease in blood carbon dioxide levels