Blood Flow Mechanics

Question 1

A stiff vessel has a high ________ but a low _________.

Answer 1

resistance; compliance

Question 2

A stretchy vessel has a high _______ but a low______.

Answer 2

compliance; resistance

Question 3

A stretchy vessel will have a _______ pulse pressure.

Answer 3

Normal pulse pressure as the walls can distend to accomodate for the blood volume.

Question 4

A stiff vessel will have a _____ pulse pressure.

Answer 4

High pulse pressure because the walls are non-distensible making it more difficult for blood to travel through the vessel. This means more pressure is required to move blood through the vessels.

Question 5

Which factors affect the change in pressure within the vessels.

Answer 5

TPR and CO - change in pressure = TPR x CO

Question 6

Which factors affect TPR?

Answer 6

The type of vessel (affects diameter, compliance).

Viscosity (thickness) of the blood

Question 7

Which vessel in the most provides the most resistance to flow - they are said to be the resistance vessels?

Answer 7

The arterioles provide the GREATEST resistance to flow - they are referred to as the resistance vessels.

Question 8

What vessels are the main determinant of TPR in the body?

Answer 8

The arterioles.

Question 9

The autonomic NS has the ability to affect the diameter of which type of vessel - in what is called vasoconstriction and vasodilation.

Answer 9

The arterioles are able to change their diameter through the effects of the autonomic nervous system. Not all vessels are able to vasoconstriction or vasodilate.

Question 10

Some pathological conditions can influence the resistance to flow through the viscosity of the blood. Anaemia causes the viscosity to______ causing a ______ in TPR

Answer 10

decrease; decrease

Question 11

The following conditions cause a _______ in the viscosity of blood.
Polycythemia
Multiple myeloma
spherocytosis

Answer 11

increase in viscosity causing an increase in the resistance to flow.

Question 12

The human body circulatory system is organised in ________ circuits.

Answer 12

Parallel circuits - this reduces the resistance encountered by the blood.

Question 13

The arterial pressure and pulmonary arterial pressure vary greater - as such what value is used to calculate the change in pressure for the flow equation.

Answer 13

Mean arterial pressure- MAP
Body - change in pressure = MAP - RAP
Lungs - change in pressure = MAP - LAP

Question 14

An increase in _______(after load/preload) causes a resulting increase in the pressure of the _________(left/right) ventricle.

Answer 14

after load; left

Question 15

Name two pathological conditions that may result in an increased after load.

Answer 15

Aortic stenosis and hypertension - the heart has top do more work to push blood into the systemic circulation.

Question 16

What is the law of Laplace?

Answer 16

The law of laplace relates to wall tension or stress on cardiac chambers and vessels.

Question 17

Using the law of Laplace, an increase in after load will cause wall tension to increase or decrease?

Answer 17

Increase in wall tension as the pressure within the left ventricle would increase as a result of increased after load.
Wall tension = P x r
———
2h

Question 18

What does “pressure overload” refer to? Describe in terms of the Law of Laplace.

Answer 18

The pressure overload refers to an increase in after load causing a resultant increase in pressure within the left ventricular wall.

Question 19

What does “volume overload” refer to? Describe in terms of the Law of Laplace.

Answer 19

The volume overload refers to an increase in the preload causing a result increase in radius of the left ventricle - the ventricle may stretch to accomodate for the greater blood volume.

Question 20

Name two pathological conditions that may result in an increased preload.

Answer 20

Chronic valvular disease (aortic/mitral regurgitation)

Question 21

Using the law of Laplace, hypertrophy of the left ventricular wall will cause the wall tension to increase or decrease?

Answer 21

The wall tension will decrease as the force is distributed over a greater mass.

Question 22

Using the Law of Laplace, why does hypertrophy of the left ventricular wall occur?

Answer 22

The left ventricular wall can thicken to compensate for chronic volume or pressure overload.

Question 23

In eccentric hypertropy the cardiac myocytes become ________ (longer/shorter)

Answer 23

longer - due to more sarcomeres being added to the myocyte in series.

Question 24

During eccentric hypertrophy the ______(mass, thickness) of the left ventricle increases.

Answer 24

The mass - the thickness of the left ventricular wall does NOT increase.

Question 25

During eccentric hypertrophy why does the thickness of the left ventricular wall not change?

Answer 25

The sarcomeres are added in series and increase in length.

Question 26

Eccentric hypertrophy is usually the result of ________(volume/pressure) overload which is associated with conditions such as aortic and mitral regurgitation.

Answer 26

volume - it is also associated with either ischemic or non-ischemic cardiac myopathy.

Question 27

What are the two types of hypertrophy?

Answer 27

Eccentric and concentric hypertropy

Question 28

During concentric hypertrophy the ______(mass, thickness) of the left ventricle increases.

Answer 28

both! The mass and thickness of the left ventricle increases

Question 29

During eccentric hypertrophy are the sarcomeres added in series or parralel?

Answer 29

Series

Question 30

During concentric hypertrophy are the sarcomeres added in series or parralel?

Answer 30

Parralel

Question 31

Eccentric hypertrophy is usually the result of ________(volume/pressure) overload which is associated with conditions such as aortic stenosis and hypertension

Answer 31

pressure overload