Cardio Physiology (Passmed)

Question 1

Where is atrial natriuretic peptide (ANP) primarily secreted from?

Answer 1

Mainly from myocytes of the right atrium and ventricle in response to increased blood volume

Question 2

Which atrium secretes more ANP?

Answer 2

Right atrium > Left atrium

Question 3

How many amino acids does ANP have and what is its second messenger?

Answer 3

28 amino acids; acts via cGMP

Question 4

How is ANP degraded?

Answer 4

By endopeptidases

Question 5

What are the effects of ANP?

Answer 5

Promotes sodium excretion, lowers blood pressure, antagonises angiotensin II and aldosterone

Question 6

What occurs during Phase 0 of the cardiac action potential?

Answer 6

Rapid depolarisation due to sodium influx

Question 7

What occurs during Phase 1 of the cardiac action potential?

Answer 7

Early repolarisation due to potassium efflux

Question 8

What occurs during Phase 2 of the cardiac action potential?

Answer 8

Plateau due to slow calcium influx

Question 9

What occurs during Phase 3 of the cardiac action potential?

Answer 9

Final repolarisation due to potassium efflux

Question 10

What occurs during Phase 4 of the cardiac action potential?

Answer 10

Resting potential restored by Na+/K+ ATPase; slow Na+ entry triggers next action potential

Question 11

How long does cardiac muscle remain contracted compared to skeletal muscle?

Answer 11

10-15 times longer

Question 12

What is the conduction velocity of atrial myocardial fibers?

Answer 12

1 m/sec

Question 13

What is the conduction velocity through the AV node?

Answer 13

0.05 m/sec

Question 14

What is the conduction velocity of Purkinje fibers?

Answer 14

2-4 m/sec (fastest in heart)

Question 15

Where is the cardiac impulse normally generated?

Answer 15

SA node in the right atrium

Question 16

What is the intrinsic firing rate of the SA node without vagal tone?

Answer 16

Around 100 discharges per minute

Question 17

Why does the SA node depolarize before the AV node?

Answer 17

Due to steeper depolarisation slope and lower resting membrane potential

Question 18

What is the role of the refractory period in cardiac cells?

Answer 18

Prevents re-stimulation, allowing ventricular filling

Question 19

What effect does sympathetic stimulation have on the SA node?

Answer 19

Increases rate of pacemaker potential via beta-1 receptors

Question 20

What effect does parasympathetic stimulation have on the heart?

Answer 20

Decreases rate via acetylcholine from vagus nerve

Question 21

What occurs during mid-diastole?

Answer 21

AV valves open, ventricles 80% filled, outflow valves shut

Question 22

What occurs during late diastole?

Answer 22

Atrial contraction completes ventricular filling (20%)

Question 23

What occurs during early systole?

Answer 23

AV valves shut, isovolumetric contraction, blood ejected

Question 24

What occurs during late systole?

Answer 24

Ventricles relax, aortic valve closes, 60ml end systolic volume

Question 25

What occurs during early diastole?

Answer 25

All valves closed, isovolumetric relaxation, AV valves reopen when atrial pressure > ventricular

Question 26

What is preload?

Answer 26

End diastolic volume

Question 27

What is afterload?

Answer 27

Aortic pressure

Question 28

What is transmural pressure?

Answer 28

Internal pressure - external pressure

Question 29

Why does a dilated heart have impaired systolic function?

Answer 29

Increased wall tension reduces contractility

Question 30

What is Starling's Law?

Answer 30

Increased EDV leads to increased stroke volume up to a limit

Question 31

Where are baroreceptors located?

Answer 31

Aortic arch and carotid sinus

Question 32

What effect does increased baroreceptor firing have?

Answer 32

Increased parasympathetic activity, decreased sympathetic activity

Question 33

Where are atrial stretch receptors located?

Answer 33

At junction of pulmonary veins and vena cava

Question 34

What is the Bainbridge reflex?

Answer 34

Increased heart rate due to increased atrial stretch

Question 35

How do you calculate stroke volume?

Answer 35

End diastolic volume - end systolic volume

Question 36

How do you calculate cardiac output?

Answer 36

Heart rate x Stroke volume

Question 37

How do you calculate mean arterial pressure (MAP)?

Answer 37

(SBP + 2*DBP)/3

Question 38

How do you calculate ejection fraction?

Answer 38

(Stroke volume / End diastolic volume) x 100

Question 39

How do you calculate systemic vascular resistance (SVR)?

Answer 39

(MAP - CVP) x 80 / CO

Question 40

What does MR.ASS stand for?

Answer 40

Mitral Regurgitation and Aortic Stenosis are Systolic murmurs

Question 41

What does MS.ARD stand for?

Answer 41

Mitral Stenosis and Aortic Regurgitation are Diastolic murmurs

Question 42

What does the P wave represent?

Answer 42

Atrial depolarisation

Question 43

What is the normal duration of the PR interval?

Answer 43

0.12 to 0.2 seconds

Question 44

What does the QRS complex represent?

Answer 44

Ventricular depolarisation

Question 45

What does the ST segment represent?

Answer 45

Plateau phase of ventricular action potential

Question 46

What does the T wave represent?

Answer 46

Ventricular repolarisation

Question 47

What does the QT interval represent?

Answer 47

Time for both ventricular depolarisation and repolarisation

Question 48

What does a large A wave indicate?

Answer 48

Tricuspid stenosis, pulmonary stenosis or hypertension

Question 49

When are cannon A waves seen?

Answer 49

Heart block, VT, nodal rhythm, ventricular pacing

Question 50

What does a V wave represent?

Answer 50

Passive atrial filling against closed tricuspid valve