pump 2

Question 1

Frank Starling Law of the heart

Answer 1

1. Heart always functions on the ascending limb of the ventricular function (Starling) curve.
2. Heart responds to an increase in end diastolic volume (EDV) by increasing the force of contraction
3. What comes in, must go out.

Question 2

Molecular basis for Starling’s law

Answer 2

1. Cardiac titin isoform is very stiff – resists stretch past a certain point.
2. Ca2+ sensitivity of myofilaments increases at longer sarcomere lengths
3. Longer sarcomere lengths change “lattice spacing” between actin and myosin, allows each cross bridge to generate more force.

Question 3

Titin is

Answer 3

1. Titin is a gigantic protein that spans Z-line to M-line in sarcomeres .
2. “Molecular spring” that determines passive elasticity of muscle.

Question 4

Skeletal muscle is more compliant due to

Answer 4

more elasticity in skeletal muscle titin isoform – can function on descending limb of length-tension relationship.

Question 5

measures of cardiac performance

Answer 5

1. blood pressure
2. stroke volume
3. ejection fraction
4. stroke work

Question 6

SV =

Answer 6

volume per beat
SV = EDV - ESV
typically 120-50 = 70 ml

Question 7

ejection fraction (EF) =

Answer 7

proportion ejected at each beat

EF = SV/EDV
EF = (EDV - ESV) / EDV = 70/120 =58%

Question 8

stroke work =

Answer 8

energy per beat (in joules)

= area under curve

Question 9

How do changes in Preload, Afterload, and Contractility independently affect cardiac performance?

Answer 9

Look at effects of stroke volume on next beat…

Question 10

determinants of cardiac output?

Answer 10

1. preload
2. afterload
3. inotropy

Question 11

preload is the load/length to which a muscle is subjected before

Answer 11

shortening

Question 12

factors that affect preload

Answer 12

1. blood volume
2. filling pressure & time
3. resistance to filling

Question 13

resistance to filling:

Answer 13

1. right atrial pressure, AV valve stenosis

2. Ventricular compliance

Question 14

what is the major determinant of preload

Answer 14

ventricular compliance

Question 15

slope of EDPR is the inverse of

Answer 15

compliance

Question 16

hypertrophy effect on compliance

Answer 16

reduces compliance

the steeper the slope, the harder it is for the ventricles to fill and the lower the EDV at any given EDP

Question 17

dilation effect on compliance

Answer 17

dilation increases compliance

Question 18

decreased compliance is

Answer 18

hypertrophy

Question 19

increased compliance is

Answer 19

dilation

Question 20

increased preload will cause

Answer 20

increase in SV on the next beat (via Starling’s law)

Question 21

afterload is the load against which a muscle

Answer 21

contracts

Question 22

factors that affect afterload

Answer 22

1. Aortic pressure: hypertension increases afterload
2. wall thickness
3. radius
4. Aortic stenosis

Question 23

Afterload is strictly defined as

Answer 23

wall stress

Question 24

major determinant of afterload is

Answer 24

aortic pressure

Question 25

increased afterload causes a

Answer 25

decreased stroke volume in the next beat

Question 26

inotrophy (contractility) is the

Answer 26

force of contraction independent of fiber length

Question 27

inotropy describes the

Answer 27

systolic function of heart

Question 28

what is the biggest affecting factor of inotropy

Answer 28

sympathetic tone

Question 29

changes in inotropy describe

Answer 29

new ventricular function (starling) curves

Question 30

increased inotropy will cause

Answer 30

increased in stroke volume on the next AND SUBSEQUENT beats