3 Control of Cardiac Output

Question 1

Blood flow to most tissues is controlled by…

Answer 1

tissue needs

microvessel feedback

Question 2

Arterial Pressure is regulated…

Answer 2

indepedent of either local blood flow or cardiac output control

Question 3

Cardiac Output

Answer 3

-quantity of blood pumped into aorta each minute (L/min)
4-6 L/min at rest, increase 4-7x with exercise
CO = HR x SVR

Question 4

What regulated Cardiac Output?

Answer 4

1.) intrinsic cardiac regulation of pump in response to changes in volume of blood flow to heart
2.) autonomic nervous system - contractility & HR
+= contractility, preload, HR, SV
-= aferload

Question 5

Stroke Volume

Answer 5

SV = EDV - ESV

-can increase with HR, but non sustain w/o help from other mechanisms

Question 6

Sympathetic Innervation of CO

Answer 6

increase, 100%

T1-T4 = cardiac accelerators

Question 7

Parasympathetic

Answer 7

slow down, can reach 0

medulla - vagal

Question 8

Heart Rate

Answer 8

more effect on CO than SV

high HR = low SV

Question 9

Bowditch (Treppe) Effect

Answer 9

-an increase in HR will also increase inotropy
-stairway phenomenon
r/t increase intracellular Ca++ with high Hr

Question 10

Preload

Answer 10

• initial stretching prior to diastole - sarcomere length
• considered to be the end-diastolic pressure when ventricle has become filled
• cannot measure directly

Question 11

LVEDV

Answer 11

Left Ventricular End Diastolic Volume

-after contraction

Question 12

LVEDP

Answer 12

Left Ventricular End Diastolic Pressure

-after contraction

Question 13

PCWP

Answer 13

Pulmonary Capillary Wedge Pressure

Question 14

CVP

Answer 14

Central Venous Pressure

Question 15

Determinants of Preload

Answer 15

Venous Blood Pressure

• vasomotor tone
• venous volume (respiration, gravity, exercise)

Question 16

Frank Starling Mechanism

Answer 16

• Intrinsic ability of heart to adapt to increasing volumes and pump out what it received.
• increased venous return = increased preload -> increased SV

Question 17

Afterload

Answer 17

• what muscle has to contract against
• resistance in circulation, not pressure
• r/t wall stress

Question 18

LaPlace’s Law

Answer 18

wall stress = ventricular pressure x ventricular radius divided by wall thickness

Question 19

Increased Afterload will lead to…

Answer 19

increased aortic pressure
increased systemic vascular resistance
aortic valve stenosis 
ventricular dilation
**shift Frank Starling curve down and to the right

Question 20

Anrep Effect

Answer 20

• an abrupt increase in afterload can cause a modest increase in inotropy
• scare = sympathetic activation -> increase inotropy in response to sudden increase in aortic pressure

Question 21

Contractility is highly related to….

Answer 21

-fiber length - think preload and sarcomere length

increased inotropy = increased ventricular SV

Question 22

Contractility Definition

Answer 22

the inherent capacity of the myocardium to contract independently of changes in afterload or preload.

• d/t intrinsic cellular mechanisms that regulate interaction between actin and myosin (independent of sarcomere length)
• CICR, calcium availability

Question 23

Factors Regulating Inotropy

Answer 23

\+ Systemic Activation
\+ Catecholemines
\+ Heart Rate
\+ Afterload (Anrep)
- Systolic Failure
- Parasympathetic Activation