Heart and Cardiovascular System

How does blood flow through the heart?

• venous blood via the superior and inferior vena cava → right atrium → passes AV valve → moves to the right ventricle

• right ventricle contracts → blood is is pumped to the lungs (systemic circulation)

• in lungs, blood enters capillaries for oxygenation,

• capillaries → left lung

• left lung → pulmonary vein → returns to the left atrium,

• left atrium → left ventricle

• left ventricle contracts and blood → aorta

• aorta → blood tissues,skeletal muscle etc. (systemic circulation)

• systemic circulation → right atrium to start cycle again

Whats the function of the AV and SV nodse/valves?

PREVENT blood flow to LEFT ATRIUM when ventricle contracts by CLOSING mitral valve

What are the characteristics and functions of veins?

take blood → heart

How do action potentials travel down the heart?

Sinoatrial (SA) node generates electrical impulse using autorhythmic (pacemaker cells)

this is why its called the “pacemaker” of the heart

• fires action potentials at a HIGHER frequency compared to AV node,

mechanical events happen AFTER electrical events

What happens after SA node generates action potential? Whats the mechanical and electrical event associated with this?

Action potential in SA node → atria

• Electrical event: atrial depolarization (caused by action potential)

• dePolarization for P WAVE on ECG

• Mechanical event: atrial contraction

What happens after action potential travels to atria? Electrical and Mechanical events?

Action potential in atria → AP gets stuck at AV NODE (intyernodal pathway)

• Electrical event: action potential DELAY

• Para, Rest = P-R SEGMENT on ECG

• Mechanical event: atria is contracting

Why does the action potential get stuck in the AV node?

the AV node delays the action potential in order to provide enough time for muscle cells in ATRIA to contract BEFORE muscle cells of VENTRICLE contract

What happens after action potential gets unstuck at the AV node?

Action potential in AV node → bundle of his

• Electrical event: VENTRICULAR depolarization and ATRIAL REPOLARIZATION (masked by QRS complex in ECG)

• ventriIQular contraction → Q

• AtrRial Repolarization → R

• = QRS on ECG

• Mechanical event: atrial RELAXATION

  ventricular depolarization

What happens after the QRS complex?

Action potential causes Ventricle to depolarize

• Electrical: NONE

• VenTricle conTraction= → S-T segment

• Mechanical event: ventricular CONTRACTION

What happens after the S-T segment?

• Electrical: NONE

• VenTricle Repolarization = → T WAVE

• Mechanical event: ventricular REPOLARIZATION

What are the roles of arteries and arterioles in the cardiovascular system? Describe their main characteristics.