Lecture 9 (Cardiovascular Physiology 3)

What does an EKG measure?

Electrical voltages generated by the heart

What term describes a normal EKG?

Sinus rhythm

What term describes an abnormally slow heart rate on an EKG?

Sinus bradycardia

What term describes an abnormally fast heart rate on an EKG?

Sinus tachycardia

*What happens during the P wave of an EKG?

Depolarization/contraction of atria

*What happens during the QRS complex of an EKG?

Depolarizaiton/contraction of ventricles (simultaneous repolarization of atria)

*What happens during the T wave of an EKG?

Repolarization of ventricles

What makes up one cardiac cycle?

One heartbeat

Why are impulses conducted through the nodes of the heart?

~0.15 second delay to allow atria to contract first

What are the units of a heart rate?

Cardiac cycles/minute

What is diastole?

Relaxation (heart fills with blood)

What is systole?

Contraction

How much blood flows into the ventricles by itself before the atria contract?

80%

What is the term for an atrial contraction?

Atrial kick

*If you are at rest and your atria fail to contract, what will happen?

Nothing

If you are exercising and your atria fail to contract, what will happen?

You will collapse

If at any time your ventricles fail to contract, what will happen?

You will collapse

What makes the first heart sound?

Closing of AV valves

What makes the second heart sound?

Closing of semilunar valves

List the stages of the cardiac cycle, starting with diastole.

1. Diastole → both chambers relaxed, ventricles fill passively

2. Atrial systole

3. Isovolumic ventricular contraction → AV valves close

4. Ventricular ejection → opens semilunar valves

5. Isovolumic ventricular relaxation → semilunar valves close

What comes first, the action potential or contraction of the heart?

Action potential

Normally, how much blood is ejected vs. end systolic volume?

60% vs. 40%

What is a normal end diastolic volume?

120 mL (up to 180)

What is a normal stroke volume output?

70 mL

What is a normal end systolic volume?

50 mL (down to 10)

At what left ventricular volume does diastolic pressure increase rapidly?

150 mL

At what left ventricular volume does systolic pressure peak and then decrease?

150 mL

What is the danger of having abnormally high blood pressure?

Prevents alignment of actin and myosin