Lecture 15 - Pressure Gradients And Blood Flow

Question 1

What is the resistance like within arteries

Answer 1

Low

Question 2

What do arteries act as in relation to pressure

Answer 2

Pressure reservoirs

Question 3

What allows for the arteries to hold extra blood after contraction

Answer 3

Elasticity

Question 4

What explains why arterial blood pressure doesn’t return to zero during diastole

Answer 4

Elastic recoil

Question 5

What are the major sites of resistance

Answer 5

Arterioles

Question 6

What are arterioles responsible for

Answer 6

The patten of blood flow distribution and the regulation of the arterial blood pressure

Question 7

What are capillaries the site of

Answer 7

Gas exchange

Question 8

What do capillaries determine

Answer 8

The distribution of extracellular fluid between the plasma and interstitial fluid

Question 9

What is the resistance like in veins

Answer 9

Low

Question 10

Why is a veins capacity adjusted

Answer 10

To facilitate the flow of blood

Question 11

What is the outer layer of blood vessels composed of

Answer 11

Collagen and elastin

Question 12

What do collagen and elastin give blood vessels

Answer 12

Strength and elasticity

Question 13

Composition of the endothelium blood vessel wall

Answer 13

5% elastic artery, 10% arteriole, 95% capillary and 20% venule

Question 14

Composition of smooth muscle blood vessel wall

Answer 14

25% elastic artery, 60% arteriole and 20% venule

Question 15

Composition of elastic tissue blood vessel walls

Answer 15

40% elastic artery and 10% arteriole

Question 16

Composition of connective tissue blood wall

Answer 16

30% elastic tissue, 20% arteriole, 5% capillary and 60% venule

Question 17

What is the interaction between pressure, flow and resistance of blood known as

Answer 17

Haemodynamics

Question 18

In the vascular system how does blood flow in relation to pressure

Answer 18

Blood always flows from a region of high pressure to one of a lower pressure

Question 19

What is the pressure exerted by a fluid known as

Answer 19

Hydrostatic pressure

Question 20

What are the units of flow

Answer 20

Volume per unit time

Question 21

What are the units of pressure difference

Answer 21

mmHg

Question 22

What is needed to calculate the flow

Answer 22

The pressure between two points and the resistance

Question 23

What is resistance

Answer 23

A measure of how difficult it is for blood to flow between two points at any given pressure difference

Question 24

What is known as the measurement of the friction impeding flow

Answer 24

Resistance

Question 25

What is the driving force of blood

Answer 25

The pressure generated by contractions of the heart

Question 26

What are the factors that affect the resistance of blood

Answer 26

The viscosity of blood, the vessel length and the vessel radius

Question 27

What does an increase in viscosity of blood cause

Answer 27

A decrease in flow

Question 28

What is the main factor that influences resistance of blood

Answer 28

The vessel diameter

Question 29

What equation states that a two-fold change in radius will produce a 16-fold change in flow

Answer 29

The poiseuille equation

Question 30

What is Laplace's law for blood vessels

Answer 30

The pressure within a vessel is equal to the tension in its walls divided by the radius of the vasculature

Question 31

What does thickness increase in proportion to

Answer 31

Diameter

Question 32

What is the average internal pressure of capillaries

Answer 32

4kPa

Question 33

What is the average internal pressure of the aorta

Answer 33

13kPa

Question 34

What is the radius and wall thickness of the capillaries

Answer 34

4 um and 1um

Question 35

What is the radius and wall thickness of the aorta

Answer 35

13mm and 20 mm

Question 36

What does the higher arteriolar resistance cause

Answer 36

A marked drop in mean pressure as blood flows through the arterioles

Question 37

Why is the drop in pressure in arterioles physiologically important

Answer 37

The pressure gradient helps to drive the blood from the heart to the tissue capillary beds

Question 38

What do arterioles convert pulsatilla arterial pressure into

Answer 38

Non-fluctuating capillary pressure

Question 39

What do the walls of arterioles include

Answer 39

A thick layer of smooth muscle

Question 40

What innervates the thick layer of smooth muscle in arterioles

Answer 40

The sympathetic nervous system

Question 41

What is the smooth muscular layer sensitive to

Answer 41

Local chemical changes and certain circulating hormones

Question 42

What is vasoconstriction

Answer 42

Contraction causes a decrease in radius which increases the resistance which causes a decrease in local blood flow

Question 43

What is vasodilation

Answer 43

During relaxation the radius is increased which decreases resistance which causes an increase in local blood flow

Question 44

What is the rate of partial contraction in arteriolar smooth muscle known as

Answer 44

Vascular tone

Question 45

What are the two factors responsible for vascular tone

Answer 45

Myogenic activity and sympathetic activity

Question 46

Why is vascular tone important

Answer 46

As it makes it possible to either decrease or increase contractile activity

Question 47

What does a change in contractility of arteriolar smooth muscle cause

Answer 47

A substantial change in resistance to flow in these vessels