Basic Cardiac Physiology

Question 1

Ohm’s Law

Answer 1

BP = CO x TPR
CO = HR x SV

BP: Blood pressure
CO: Cardiac output
TPR: Total peripheral resistance
HR: Heart rate
SV: Stroke Volume

Question 2

Pulse pressure

Answer 2

systole - diastole

Question 3

Mean arterial pressure (MAP)

Answer 3

(2/3 Diastole) + (1/3 Systole)

Question 4

Central Venous Pressure (CVP)

Answer 4

~ Right Atrial Pressure

Question 5

Normal pressure at the various parts of adult circulation

Answer 5

Large arteries:

Question 6

Physiologic basis for normal ECG tracing

Answer 6

P Wave: atrial depolarization
QRS Complex: ventricular depolarization
T Wave: ventricular repolarization

Question 7

Master pacemaker of the heart

Answer 7

Sinoatrial node (SA node)

Question 8

Cause of SA Node depolarization

Answer 8

Calcium influx

Question 9

Types of 2nd degree AV block

Answer 9

Mobitz I: prolongation of PR interval before dropped QRS complex

Mobitz II: no prolongation of PR interval before dropped QRS complex

Mnemonic:

• Think of Roman Numeral I that is getting taller -> prolongation of PR interval in Mobitz I
• Think of Roman Numeral II with equal heights between the two letter “I”s -> no prolongation of PR interval in Mobitz II

Question 10

Most metabolic organ

Answer 10

brain

Question 11

Most efficient extractor of oxygen from the blood

Answer 11

heart

Question 12

Bainbridge reflex

Answer 12

Increase in venous return increases heart rate

Question 13

Frank-Starling mechanism

Answer 13

Increase in venous return increases stroke volume

Question 14

Stokes-Adams syndrome

Answer 14

AV block that causes fainting due to the initially suppressed rate of the Purkinje fibers

Question 15

Cushing reflex

Answer 15

Hypertension, irregular respiration and bradycardia due to activation of CNS ischemic response and baroreceptor reflex in patients with increased intracranial pressure