Cardiac Contraction And Relaxation

Question 1

Cardiomyocytes constitute how much of the total ventricular volume?

Answer 1

75%

Question 2

Major component of extracellular matrix?

Answer 2

Myofiber

Question 3

Also known as the calcium release channels

Answer 3

Ryanodine receptors

Question 4

Site of calcium binding in the myocytes that initiate contraction?

Answer 4

Troponin C

Question 5

The interaction of the myosin heads with the actin filaments that is switched on when calcium binds is known as?

Answer 5

Cross-bridge cycling

Question 6

Contraction strength is independent of sarcomere length (eg. Increased itnracellular calcium)

Answer 6

Positive inotoropic state

Question 7

Central regulator of cardiac contraction and relaxation

Answer 7

Calcium

Question 8

Calcium channel where dihydropyridines act on?

Answer 8

L - type calcium channels

Question 9

Shape of ventricular myocytes

Atrial myocyte

Purkinjie cells

Answer 9

VM - long and narrow

AM - eliptical

PC - long and broad

Question 10

This cell organelle is involved in the Interaction of thick and thin filaments during contraction cycle

Answer 10

Myofibril

Approx 50-60% of cell volume

Question 11

This cell organelle is involved in the transmission of electrical signal from sarcolema to cell interior

Answer 11

T-system

Question 12

This cell organelle takes up and releases calcium during contraction cycle

Answer 12

Sarcoplasmic reticulum

Question 13

Organelle involved in the calcium storage and release?

Answer 13

SR terminal cisternae

Question 14

Orgagnelle involved in control of ionic gradients, channels for ions (action potential), maintenance of cell integrity, receptor for drugs and hormones

Answer 14

Sarcolemma

Question 15

Organelle where cytosolic volume within which calcium rises and falls

Answer 15

Sarcoplasm

Question 16

Troponin that stabilises troponin T and tropomyosin to block cross-bridge binding?

Answer 16

Troponin I

Question 17

A large elastic protein that connects the myosin and the M-line to the Z-line

Answer 17

Titin

Question 18

This phase of the cardiac action potential corresponds to plateau phase

Answer 18

Phase 3

Question 19

This phase of cardiac action potential corresponds to resting state

Answer 19

Phase 4

Question 20

Phase of cardiac action potential where calcium channels open to balance the potassium rectifiers

Answer 20

Phase 3

Question 21

Resting membrane potential is how many mV?

Answer 21

-90

Question 22

Threshold for cardiac muscle action potential?

Answer 22

-70 mV

Question 23

This effect occurs when there is increased uptake of calcium by the sarcoplasmic reticulum leading to enhance relaxation of the cardiac myocytes?

Answer 23

Lusitropic effect

Question 24

Type of calcium channel that has a more negative voltage, short bursts of opening and do not interact with calcium antagonist drugs.

Answer 24

T-type (tamad)

Question 25

Type of calcium channel concentrated in the T tubules and jSR. Inihbitted by CCB drugs.

Answer 25

L type calcium channels

Question 26

This refer to increase or decrease in coduction of action potential

Answer 26

Dromotropy

Question 27

Phase of cardiac cycle after mitral closure and before aortic valve opening where the volume remains fixed is known as?

Answer 27

Isovolumic contraction

Question 28

Normally LV pressure is between how many mmHG?

Answer 28

8-15 mmHG

Question 29

This aortic recoil maintains blood flow from the left ventricle to the aorta despite rapid decline

Answer 29

Windkessel effect

Question 30

Phase where the aortic valve and the mitral valve are closed but no change in the LV volume occurs after systole

Answer 30

Isovolumic relaxation

Question 31

Lasts from the start of isovolumic contraction to the peak of the ejection phase

Answer 31

Physiologic systole

Question 32

The interval between the first heart sound (M1) to the closure of the aortic valve (A2)

Answer 32

Cardiologic systole

Question 33

This heart sound corresponds to rapid filling of the ventricle or increased LV diastolic pressure, wall stiffness, or rate of filling

Answer 33

Protodiastole or S3

Question 34

Describes the degree of myocardial stretch or distention before contraction has started and best presented by LVEDV

Answer 34

Preload

Question 35

Refers to forces opposing LV ejection. More accurately described as aortic impedance or elastance

Answer 35

Afterload

Question 36

Used to measure venous filling pressure or stroke volume indirectly

Answer 36

Swan-ganz catheter

Question 37

Refers to the true distending pressure that determines LV preload volume calculated by EDP - external pericardial pressure

Answer 37

Left ventricular transmural pressure Estimated by difference between EDP and right atrial pressure

Question 38

A slow inotropic adaptation where the inotropic state of the heart increases such as when aortic pressure is elevated abruptly

Answer 38

Anrep effect

Question 39

Wall stress = (pressure x radius)/ (2 x wall thickness)

Answer 39

Laplace’s law Mnemonic S= PxR/ 2xWT SPRWT “SPRoWT”

Question 40

This is the wall stretch at the end of diastole where the resting length of the sarcomere is maximal

Answer 40

Preload

Question 41

This reflects the 3 major components of afterload (PVR, Arterial compliance, peak intraventricular pressure)

Answer 41

Peak systolic wall stress

Question 42

This measure of the LV afterload is independent of the heart size or wall thickness

Answer 42

Aortic impedance or elastance

Question 43

Estimated by the relationship between end-systolic LV pressure and SV

Answer 43

Arterial elastance

Question 44

An increase in heart rate progressively enhances the force of ventricular muscle contraction. This effect is known as?

Answer 44

Bowditch staircase phenomenon Alternative name is treppe

Question 45

3 determinants of myocardial o2 demand

Answer 45

Preload Afterload Heart rate

Question 46

SBPxSVxHR = ?

Answer 46

Minute work

Question 47

External cardiac work can account for how many percent of myocardial o2 demand?

Answer 47

40%

Question 48

In patients with HFrEF what is the picture of the pressure-volume curve?

Answer 48

Shifted to the far right ESVPR (end diastolic vol pres relationship) very shallow

Question 49

Occurs mid diastole when LA and LV pressure is almost equal. Contributes less than 5% of LV filling

Answer 49

Diastasis

Question 50

Atrial systole constitutes how many percent of LV diastolic filling?

Answer 50

15-25%

Question 51

Reflex that causes Increase in heart rate secondary to increase in CVP or return of blood to the atrium?

Answer 51

Bainbridge reflex