Force Generation by Heart

Question 1

cardiac muscle is striated (T/F)

Answer 1

True

Question 2

What are cardiac myocytes electrically coupled by?

Answer 2

gap junction

Question 3

Define gap junctions

Answer 3

protein channels which form low resistance electrical communication pathways between neighbouring myocytes

Question 4

gap junctions importance

Answer 4

ensure each electrical excitation reaches all cardiac myocytes

Question 5

desmosomes importane

Answer 5

• provide mechanical adhesion between adjacent cardiac cells

- tension developed by 1 cell transmitted to next

Question 6

define myofibrils

Answer 6

contractile units of muscle

Question 7

actin are _____ filaments

Answer 7

thin

Question 8

myocin are ____ filaments

Answer 8

thick

Question 9

actin and myocin are arranged into what?

Answer 9

sacromere

Question 10

how is muscle tension produced?

Answer 10

sliding of actin filaments on myocin filaments

Question 11

force generation is dependent on?

Answer 11

ATP-dependent interactions

Question 12

What is required for contraction and relacation

Answer 12

ATP

Question 13

What is Ca++ required for

Answer 13

Switching on cross bridge formation

Question 14

Define diastole

Answer 14

Ventricular muscle relaxes

Question 15

Define systole

Answer 15

Ventricular muscle contracts

Question 16

Long refractory period importance

Answer 16

prevents generation of tetanic contraction

Question 17

define refractory period

Answer 17

period following action potential in which it’s not possible to produce another action potential

Question 18

Contraction of ventricular muscle ejects?

Answer 18

Stroke Voume

Question 19

Define SV

Answer 19

vl of blood ejected by each ventricle per heart beat

Question 20

Calculate SC

Answer 20

SV = End diastolic vl - end systolic volume

Question 21

What is SV regulated by

Answer 21

Intrinsic + extrinsic mechanisms

Question 22

explain intrinsic

Answer 22

within heart muscle itself

Question 23

explain extrinsic

Answer 23

nervous and hormonal control

Question 24

deine cardiac output

Answer 24

vl blood pumped by each ventricle per minute

Question 25

calculate CO

Answer 25

SV x HR

Question 26

what causes changes in stroke volume

Answer 26

changes in

• diastolic length
• myocardial fibres

Question 27

define diastolic length

Answer 27

vl of blood within each ventricle at end of diastole

AKA End Diastolic Volume

Question 28

what does EDV determine

Answer 28

Cardiac preload

Question 29

What is EDV determined by

Answer 29

venous return to heart

Question 30

Explain Frank-Starling Mechanism

Answer 30

• Relationship between end diastolic volume and stroke volume
• greater EDV = greater stroke volume

Question 31

How is optimal length in cardiac muscle achieved

Answer 31

stretching muscle (Frank-Starling mechanism)

Question 32

Explain starling’s law

Answer 32

RIght

venous return to RA increases = EDV right ventricle increases = increased Sv in pulmonary artery

Left

venous return to LA from pulmonary vein increases = EDV of LV increases = increased SV in aorta

Question 33

Deine afterload

Answer 33

resistance into which heart = pumping

after heart contracted

Question 34

What does Frank-Starling mechanism partially compensate for

Answer 34

Decreased Sv caused by increased AL