12/2/2014 Medical Physiology Systemic Circulation Amit S. Dhamoon Flashcards Preview

► Med Misc 18 > 12/2/2014 Medical Physiology Systemic Circulation Amit S. Dhamoon > Flashcards

Flashcards in 12/2/2014 Medical Physiology Systemic Circulation Amit S. Dhamoon Deck (40):
1

What does the concept of compliance refer to in general?

Compliance = V/P

* blood vessels have finite compliance

2

In blood vessels, the greater the volume of fluid, the ___ the pressure

greater

3

Define compliance (C) of an elastic vessel

Proportionality factor
that relates the change in volume, ∆V, to a change in transmural pressure, ∆P(tm)
∆V = C∆P(tm)
or
C = ∆V/∆PTM

4

What is another name for compliance?

Capacitance (ml/mm Hg)

5

Define transmural pressure

P(tm) --> difference in pressure between the inside and the outside of the vessel

6

A rigid tube has a compliance of ___

zero

7

Define elastance (E)

Inverse of compliance

E = ∆P(tm)/∆V

8

Define distensibility (D) or specific compliance

Fractional change in volume for a given change in pressure

D = ∆V/V∆P(tm) = C/V.

9

What determines vascular compliance?

The relative proportion and arrangement of smooth muscle, and elastin and collagen fibers in the vessel wall

10

Describe the function of each type of vessel

1) aorta
- conduit of blood from the heart
- high pressure vessel.

2) arterioles
- resistance vessels
- regulate blood flow through individual organs
- affected by sympathetic nervous system

3) capillaries
- exchange vessels

4) veins
- capacitance vessels
- contain >50% of blood volume

11

Because blood vessels are ___, they can expand and contract depending upon the pressure, changing blood volume contained within

distensible

12

Compliance is the medically important measure of how the distensible ___ changes volume with pressure

blood vessel

13

Vascular compliance is determined by arrangement of ___ and ___ and is not homeostatically regulated parameter like pressure

elastic fibers; smooth muscle

14

Compliance is measured from the ___ of a Pressure-Volume curve

slope

15

Another way to quantify the elastic properties of vessels is ___

distensibility

16

Why do arteries function as resistance vessels?

They have low volume capacity, expand modestly and maintain resistance over wide pressure levels

17

Why do veins function as volume reservoirs or capacitance vessels?

They expand greatly (also change shape) with small pressure changes due to the high compliance and have large volume changes

18

With increasing age, vascular compliance ___ dramatically, and the heart must work
___ to pump blood through stiffer vessels

decreases; harder

19

A given stroke volume would produce a ___ pulse pressure in older individuals than in younger ones

greater

20

With increasing age the Windkessel effect is ___, causing pulsatile flow to persist in the capillaries

decreased

21

Regular exercise ___ cardiac contractility and stroke volume so that the heart may pump
blood through vessels that are stiffer and that may also have higher resistance due to ___

increases; atherosclerosis

22

What is the Windkessel effect?

German for wind chamber --> the storage of blood during systole by the aorta, pulmonary artery and their major branches

23

What is the consequence of the Windkessel effect?

The maintenance of blood flow during diastole

24

For a given cardiac output, Q, the mean pressure decreases with increasing distance from the heart in accordance with Poiseuille's law:

P2 = P1 - (8ηQ/πr4)L

25

The greatest pulse pressure is in the ___

left ventricle

26

Why does blood flow?

Because cardiac contractions create pressure in the fluid contained within the heart, thus establishing a pressure gradient of about 100 mm Hg between the aorta and the vena cava

27

Is the pressure on the arterial side pulsatile in the systemic circulation?

Yes

28

What facilitates the damping of the pressure oscillations and the steadiness of the blood pressure as the large resistance of the smaller arterioles is encountered?

The Windkessel effect

29

Why is pulmonary resistance less than systemic resistance?

Because in the pulmonary capillaries the pressure remains pulsatile, oscillating between lower limits than in the systemic circulation

30

The arterial pulse contour shows the time course of the ___ in the arteries of the systemic circulation during a single cardiac cycle

transmural pressure

31

As the heart beats, a continuous sequence of ___ pressure waves is generated at a frequency of 1-2 Hz (hertz, cycles per second)

pulsatile

32

Define systolic pressure, Ps

Maximum pressure reached by the arterial pressure as blood is ejected from the heart during systole

33

Define diastolic pressure, Pd

Minimum pressure reached by the arterial pressure as the heart relaxes and refills during diastole

34

The mean arterial pressure is equal to the steady pressure required to maintain the ___ through the total peripheral resistance

cardiac output

35

What does the shape of arterial pulse contour reflect?

Events of cardiac cycle and elastic properties of the vessels

36

What is the anacrotic limb?

Rising part of aortic pressure wave

37

What causes the anacrotic limb?

Blood entering aorta from left ventricle during systolic ejection

38

What is peripheral runoff?

Flow of blood from arteries into capillaries

39

What is the dicrotic notch or incisura?

Momentary reversal of blood flow, which closes the aortic valves and creates a transient increase in aortic pressure

40

Pulse pressure is directly proportional to ___ and inversely proportional to ___

stroke volumen; compliance

Decks in ► Med Misc 18 Class (36):