Cardiovascular Responses

Question 1

How do arteries function in relation to CV responses

Answer 1

• Large arteries distend and recoil to dampen pressure changes.
• They cushion the rest of the arterial system from the large pressure waves generated by the ventricle.
• The arteries function as pressure reservoirs that are ready to release pressure for moving blood when the arterial walls recoil.
• Blood flow smooths to continuous laminar flow when the blood reaches the capillary beds.

Question 2

What are the properties elastin and collagen that give arteries their characteristics?

Answer 2

1. Elastin - fibrous molecule found in arterial walls, that stretches easily to uniformly distribute the pressure created by the ventricle
2. As the diameter and pressure in the artery increase, the force inside the artery is gradually transferred to the more rigid collagen fibers.

Question 3

What is Poiseuille’s Law:

Answer 3

Resistance to flow = (fluid viscosity x tube length) / (radius of tube)^4

Question 4

What does Poiseuille’s Law tell us?

Answer 4

• A small change in blood vessel radius dramatically alters blood flow.
–> A 33% increase in the radius of the arterioles will reduce the resistance of the blood flow by 400%.
• The longer the vessel, the more resistance to flow (lower pressure).

Question 5

What are the 4 main determinants that influence BP?

Answer 5

1. Cardiac Output: If you increase HR or SV you will increase CO and thus increase BP.
2. Blood Volume – If you decrease or increase blood volume you will subsequently decrease or increase BP.
3. Overall Compliance – The elastic properties of the blood vessels.
4. Total Peripheral Resistance – Resistance created by all the blood vessels in systemic circulation.

Question 6

Where are arterial baroreceptors found?

Answer 6

carotid sinus and the aortic arch.

Question 7

What is the fxn of arterial baroreceptors?

Answer 7

• Responsible for regulating heart rate and cardiac contractility through sympathetic and parasympathetic channels stemming from the CNS.

Question 8

How does the firing rate of the arterial baroreceptors change with changes in MABP?

Answer 8

• With greater decreases MABP, the arterial baroreceptor firing rate is reduced, causing a SNS mediated arterial vasoconstriction and both a PNS and SNS mediated increase in HR.
• The initial increase in HR is due to withdrawal of PNS activity.

Question 9

Where are cardio-pulmonary baroreceptors found?

Answer 9

• Found in the right atrium, ventricles, and pulmonary arteries.

Question 10

How is the cardiopulmonary baroreflex triggered?

Answer 10

• A decrease in central venous pressure (CVP) triggers the cardiopulmonary baroreflex to elicit a sympathetic mediated vasoconstrictor response in muscles allowing for greater venous return.