Section 2D

Question 0

Preload is directly influenced by what?

Answer 0

EDV

Question 1

What is the preload

Answer 1

The load or stretch on the ventricular cardiac muscle before it contracts

Question 2

Describe how the preload is confirmed by the Frank-Starling Law of the Heart

Answer 2

The more the ventricles are filled, the more they will eject during systole

Question 3

How is Heterometric and Homometric regulation of SV different

Answer 3

Heterometric: Different Volumes (EDV), different volumes change the force of contractability

Homometric: Same Volume (EDV), SNS can increase the force of contracability independent of volume

Question 4

Preload is would be considered what type of SV regulation

Answer 4

Heterometric Regulation

Question 5

Describe Inotropism

Answer 5

Increase in cardiac contractability independent of Frank-Starling’s law. SNS has a positive iontropic effect on the heart meaning it increases the SV at a constant preload

Question 6

Enhanced contractibility results in what?

Answer 6

Lower ESV and increased SV

Question 7

SNS stimulation via B1 receptors increases the force of contractibility through what two mechanisms:

Answer 7

1. Increases the inward Ca current during the plateau phase of each cardiac action potential
2. It increases the activity of the SERCA pumps; as a result more Ca is accumulated by the SR and thus more Ca is available for release in subsequent beats

Question 8

What is the afterload

Answer 8

The load the heart must overcome after and while it contracts. Afterload is essentially the back pressure exerted on the aortic and semilunar valves by arterial blood in the aorta and pulmonary trunk.

Question 9

What must happen with a Large Afterload

Answer 9

The ventricle must pump blood against a higher pressure

This results in decreased SV

Question 10

What must happen with a Small Afterload

Answer 10

The ventricle pumps blood against a lower pressure

Results in increased SV

Question 11

What are often used to decrease afterload

Answer 11

Vasodilators

Question 12

Cardiac Output or performance is enhance by : (4)

Answer 12

Increased Preload
Increased Inotropy (SNS)
Increased Heart Rate
Decreased Afterload

Question 13

CO or performance is depressed by: (4)

Answer 13

Decreased Preload
Decreased Inotropy (SNS)
Decreased HR
Increased Afterload

Question 14

Explain Frank-Starling’s law of the heart

Answer 14

1. Increases in EDV results in increases of ventricular fiber length. This produces increased tension.
2. Stretch of Myocardium may enhance affinity of Troponin C for Ca. Also may increase Ca uptake and release from SR