Cardiac Cycle

Question 1

at what phase is the heart relaxed and filling with blood?

Answer 1

diastole

Question 2

what event marks the beginning of diastole?

Answer 2

AV opens

Question 3

what are the 3 stages of diastole called, in order?

Answer 3

(after isovolumic relaxation)
1. rapid inflow
2. diastasis
3. atrial systole

Question 4

what occurs during rapid inflow?

Answer 4

• AV valve open: ventricle is filled with blood from atria
• atrial volume & pressure drop
• ventricular volume & pressure increase

Question 5

what occurs during diastasis?

Answer 5

(reduced filling)
AV valves still open: ventricular volume & pressure slowly increase

Question 6

what occurs during atrial systole?

Answer 6

• atria contract (a-wave) -> push last 20% blood into ventricle
• increased ventricular pressure closes AV valve (S1)

Question 7

what event marks the end of diastole?

Answer 7

AV valve closes

Question 8

what must happen in order for the aortic valve to open?

Answer 8

overcome diastolic pressure

Question 9

what phase occurs after the AV valve closes?

Answer 9

isovolumic contraction

Question 10

what occurs during isovolumic contraction?

Answer 10

• atria relax (c-wave)
• ventricle contracts
• ventricular volume constant (no blood ejected)
• ventricular pressure increases

Question 11

what event marks the end of isovolumic contraction?

Answer 11

aortic valve opens

Question 12

what occurs during the ejection stage of systole?

Answer 12

• aortic valve is open
• ventricle contracts -> blood ejected from heart (ventricular volume decreases)

Question 13

what event marks the end of systole?

Answer 13

aortic valve closes

Question 14

what occurs when the aortic valve closes?

Answer 14

isovolumic relaxation

Question 15

what occurs during isovolumic relaxation?

Answer 15

• aortic valve closes (S2)
• AV valve still closed = no change in ventricular volume
• ventricular pressure decreases
• slow flow of blood into atria (v-wave)

Question 16

what marks the end of isovolumic relaxation?

Answer 16

atrial pressure > ventricular pressure = AV valve opens

Question 17

in the atrial pressure curve, what does the a-wave represent and when does it occur?

Answer 17

• atrial contraction
• diastole: atrial systole

Question 18

in the atrial pressure curve, what does the c-wave represent and when does it occur?

Answer 18

• ventricular contraction: AV valve bulges as ventricular P increases
• isovolumic contraction

Question 19

in the atrial pressure curve, what does the v-wave represent and when does it occur?

Answer 19

• slow flow of blood into atria while AV valve closed
• isovolumic relaxation

Question 20

why is atrial pressure always close to 0?

Answer 20

atria is a vein

Question 21

what does the first heart sound (S1) represent?

Answer 21

AV valve closing (end of diastole)

Question 22

what does the second heart sound (S2) represent?

Answer 22

aortic valve closing (end of systole)

Question 23

what causes a potential third heart sound?

Answer 23

rapid filling of ventricles

Question 24

what causes flaccid contraction of the heart?

Answer 24

excess serum K+ or low Ca++

Question 25

what causes spastic contraction of the heart?

Answer 25

excess serum Ca++

Question 26

what does the P wave in an ECG represent?

Answer 26

atrial depolarization

Question 27

what does the QRS complex in an ECG represent?

Answer 27

ventricular depolarization

Question 28

what event is "covered up" by the QRS complex?

Answer 28

atrial repolarization

Question 29

what does the T wave in an ECG represent?

Answer 29

ventricular repolarization

Question 30

at what phase does the heart receive blood supply (epicardial flow)?

Answer 30

diastole

Question 31

what cellular event occurs during the rising phase of cardiac action potential?

Answer 31

voltage-gated fast Na+ and slow Ca++ channels open (both in)

Question 32

what cellular event occurs during the plateau phase of cardiac action potential?

Answer 32

Ca++ activated Ca++ release from SR via ryanodine receptor

Question 33

what cellular event occurs during the falling phase of cardiac action potential?

Answer 33

K+ channels open (out)

Question 34

what controls the RMP of cardiac muscle?

Answer 34

Na/K ATPase pump and Na/Ca antiporter

Question 35

in which phase of the ventricular muscle action potential is K+ permeability the highest?

Answer 35

3 (falling phase) (K+ permeability of ventricle greatly increases, causing more negative membrane potential)

Question 36

the AV valve is also known as the ____ valve

Answer 36

mitral