L08a: Arterioles And Vascular Resistance

Question 1

What are the factors that determine resistance

Answer 1

Viscosity of blood
Length of tubules
Radius

Question 2

What happens to the resistance as length of tubules increase

Answer 2

Increase

Question 3

What happens to the resistance in vessels as blood viscosity increases

Answer 3

Increases

Question 4

What happens to the resistance in vessels as radius increases

Answer 4

Decreases

Question 5

Which factors affecting the resistance has the biggest effect

Answer 5

Radius

Question 6

What are arterioles also known as

Answer 6

Resistance vessels

Question 7

How can arterioles increase the radius

Answer 7

By vasodilation

Question 8

How can arterioles decrease their radius

Answer 8

By vasoconstriction

Question 9

What happens to the blood flow when vasodilation occurs

Answer 9

Blood flow increases

Question 10

What happens to the blood flow when vasoconstriction occurs

Answer 10

Blood flow decreases

Question 11

What is vasodilation and vasoconstriction controlled by

Answer 11

Endothelial factors (associated with the blood vessels)
Local mechanism 
Central neural mechanism
Hormonal mechanism

Question 12

Why is a parallel arrangement beneficial in terms of blood flow of a particular organ

Answer 12

If an arteriole changes it diameter by vasoconstriction or vasodilation the blood flow of that organ is only affected, the other organs do not have their blood flow altered.

Question 13

Where are endothelial cells found

Answer 13

Walls of vessels

Question 14

What substances do endothelial cells produce

Answer 14

Vasoactive substances

Question 15

Which muscle cells do vasoactive substances affect

Answer 15

Smooth muscle cells

Question 16

What are the triggers that cause the release of vasoactive substances from endothelial cells

Answer 16

Sheer stress
Paracrine hormones
Circulating hormones
Hypoxia

Question 17

How do we get sheer stress

Answer 17

Increase in blood flow

Question 18

What is the role of vasoactive substances

Answer 18

To cause vasodilation or vasoconstriction

Question 19

Name vasoactive substances that cause vasodilation

Answer 19

Nitrous oxide
Prostaglandins
Endothelium derive hyperpolarisation factor

Question 20

What enzyme synthesises nitrous oxide in the endothelial cells

Answer 20

Nitric oxide synthase

Question 21

Describe the activity that occurs when nitrous oxide is produced

Answer 21

Lead to a decrease in calcium in smooth cells so vasodilation occurs by relaxation of smooth muscle cells
This increases blood flow

Question 22

What happens to nitrous oxide in coronary heart disease

Answer 22

Nitrous oxide is not produced and this leads to a decreased blood flow.

Question 23

Name vasoactive substances that cause vasoconstriction

Answer 23

Endothelins
Thromboxane
PGF

Question 24

How do endothelins cause vasoconstriction in smooth muscle cells

Answer 24

Cause the release of intracellular calcium

Question 25

What are local factors

Answer 25

Substances produced as a result of metabolism

Question 26

Name local factors

Answer 26

Adenosine Potassium Carbon dioxide Hydrogen ions

Question 27

Do local factors cause vasodilation or vasoconstriction (think about what we want the blood flow to be like when there is a buildup of metabolic activity)

Answer 27

It will vasodilation to increase the blood flow.

Question 28

What is the increase in blood flow due to an increase in metabolic activity known as

Answer 28

Active/ functional hyperaemia

Question 29

What is the BUILD up of metabolic products causing an increase in blood flow called

Answer 29

Reactive hyperaemia

Question 30

What is autoregulation

Answer 30

When the lumen of the vessel expands, smooth muscle contracts to restore the original diameter

Question 31

Which organs have auto-regulation in their blood vessels

Answer 31

Kidney Cerebral Coronary circulation

Question 32

What happens to the vessels with auto-regulation when pressure falls

Answer 32

Vasodilation

Question 33

What happens when the arterial pressure falls past the lower limit

Answer 33

Autoregulation is lost

Question 34

What happens to the blood vessels with auto-regulation when pressure increases

Answer 34

Vasoconstriction occurs

Question 35

What happens to the auto regulation when pressure continues to increase past the upper limit

Answer 35

Auto regulation is lost

Question 36

What is the central neural mechanism of vessels

Answer 36

The control of blood vessels by the sympathetic nervous system

Question 37

Do blood vessels have parasympathetic innervation

Answer 37

Only found in blood vessels of the genital organs and salivary glands

Question 38

What does an increase in sympathetic activity of the blood vessels cause

Answer 38

Vasoconstriction

Question 39

What does a decrease in the sympathetic activity cause

Answer 39

Vasodilation

Question 40

Which neurotransmitter is released from the sympathetic nervous system that causes vasoconstriction

Answer 40

Noradrenaline

Question 41

Which receptors do noradrenaline act on in the blood vessels

Answer 41

Alpha 1 adrenoceptors

Question 42

What other receptor does noradrenaline bind weakly to on the arterioles

Answer 42

Beta 2 adrenoceptors

Question 43

What does circulating adrenaline cause

Answer 43

Vasodilation

Question 44

What receptor does circulating adrenaline bind to

Answer 44

Beta 2 receptors

Question 45

What does the hormonal mechanism involve for controlling diameter of the vessels

Answer 45

ADH | Angiotensin 2

Question 46

What does ADH cause

Answer 46

Vasoconstriction

Question 47

What does angiotensin 2 cause

Answer 47

Vasoconstriction

Question 48

When is angiotensin 2 produced

Answer 48

When the renal artery pressure falls

Question 49

Where does constriction have to occur for the TPR to increase and therefore the ABP to increase

Answer 49

Constriction of arterioles in multiple organs

Question 50

Give an example when reactive hyperaemia occurs

Answer 50

Weight lifting when there is no blood flow

Question 51

Which responce allows autoregulation

Answer 51

Myogenic responce

Question 52

What is the myogenic responce

Answer 52

When the walls are stretched and in response contract

Question 53

What receptors does noradrenaline bind to

Answer 53

Alpha 1 and beta 2 receptors

Question 54

What does circulating adrenaline cause to the blood vessel

Answer 54

Vasodilation

Question 55

What receptor does adrenaline act on

Answer 55

Beta 2