C- Heart as a Pump

Question 1

Cardiac output =

Answer 1

heart rate x stroke volume

CO = HR x SV

Question 2

Cardiac Output (CO) is the volume of blood pumped per minute by the heart (_______ at rest)

Answer 2

~5 L/min

Question 3

stroke volume

Answer 3

amount of blood pumped per beat

Question 4

stroke volume factors

Answer 4

Preload (venous return)

Afterload = resistance to flow (normally aortic pressure)

Strength of contraction

Question 5

Length-dependent intrinsic regulation (Starling’s Law) and length-independent regulation via sympathetic nervous system

Answer 5

Strength of contraction mechanisms

Question 6

The load/length to which a muscle is subjected before shortening.

Answer 6

PRELOAD

Question 7

The load against which a muscle contracts.

Answer 7

AFTERLOAD

Question 8

Difference between SPVR and EDPVR
Represents ACTIVE tension (i.e., that generated by contraction)
Ascending & descending limbs
represented by?

Answer 8

Ventricular Function (Starling) Curve

Question 9

Heart always functions on the ascending limb of the __________ (Starling) curve

Answer 9

ventricular function

Frank-Starling Law of the Heart- What comes in, must go out.

Question 10

Heart responds to an increase in end diastolic volume (EDV) by increasing the force of ________

Answer 10

contraction

Frank-Starling Law of the Heart- What comes in, must go out.

Question 11

Starling’s Law is an_________ property of the heart.

Answer 11

INTRINSIC

• independent of autonomic nervous system regulation
• analogous to, and dependent on, the sarcomere length-tension relationship

Question 12

• independent of autonomic nervous system regulation
• analogous to, and dependent on, the sarcomere length-tension relationship
• Parts of what law?

Answer 12

Starling’s Law, an INTRINSIC property of the heart.

Question 13

Ejection Fraction (EF) = _____________

Answer 13

Proportion ejected at each beat

pv loop ex:
= SV/EDV
= (EDV – ESV)/EDV = 70/120 = 58%

Question 14

Factors that affect preload

Answer 14

blood volume
filling pressure & time
resistance to filling
  right atrial pressure, AV valve stenosis
  Ventricular compliance

Question 15

Factors that affect afterload

Answer 15

Aortic pressure is the major determinant of afterload

defined as wall stress, so wall thickness and radius also affect afterload

Aortic stenosis can also affect afterload

Question 16

hypertension increases________

Answer 16

afterload

Question 17

For left ventricle, preload ~ _____________

Answer 17

end diastolic volume.

Question 18

For left ventricle, afterload ~ _________

Answer 18

aortic pressure

Question 19

Increased afterload _______ stroke volume on next beat

Answer 19

decreases

Question 20

Force of contraction independent of fiber length

describes systolic function of heart
Sympathetic tone is the biggest factor affecting inotropy

Answer 20

INOTROPY (CONTRACTILITY):

Question 21

Changes in________ describe new ventricular function (Starling) curves

Answer 21

inotropy