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CVS > L08a: Arterioles And Vascular Resistance > Flashcards

L08a: Arterioles And Vascular Resistance Flashcards

1
Q

What are the factors that determine resistance

A

Viscosity of blood
Length of tubules
Radius

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2
Q

What happens to the resistance as length of tubules increase

A

Increase

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3
Q

What happens to the resistance in vessels as blood viscosity increases

A

Increases

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4
Q

What happens to the resistance in vessels as radius increases

A

Decreases

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5
Q

Which factors affecting the resistance has the biggest effect

A

Radius

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6
Q

What are arterioles also known as

A

Resistance vessels

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7
Q

How can arterioles increase the radius

A

By vasodilation

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8
Q

How can arterioles decrease their radius

A

By vasoconstriction

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9
Q

What happens to the blood flow when vasodilation occurs

A

Blood flow increases

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10
Q

What happens to the blood flow when vasoconstriction occurs

A

Blood flow decreases

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11
Q

What is vasodilation and vasoconstriction controlled by

A 
Endothelial factors (associated with the blood vessels)
Local mechanism 
Central neural mechanism
Hormonal mechanism
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12
Q

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

A

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.

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13
Q

Where are endothelial cells found

A

Walls of vessels

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14
Q

What substances do endothelial cells produce

A

Vasoactive substances

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15
Q

Which muscle cells do vasoactive substances affect

A

Smooth muscle cells

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16
Q

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

A

Sheer stress
Paracrine hormones
Circulating hormones
Hypoxia

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17
Q

How do we get sheer stress

A

Increase in blood flow

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18
Q

What is the role of vasoactive substances

A

To cause vasodilation or vasoconstriction

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19
Q

Name vasoactive substances that cause vasodilation

A

Nitrous oxide
Prostaglandins
Endothelium derive hyperpolarisation factor

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20
Q

What enzyme synthesises nitrous oxide in the endothelial cells

A

Nitric oxide synthase

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21
Q

Describe the activity that occurs when nitrous oxide is produced

A

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

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22
Q

What happens to nitrous oxide in coronary heart disease

A

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

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23
Q

Name vasoactive substances that cause vasoconstriction

A

Endothelins
Thromboxane
PGF

24
Q

How do endothelins cause vasoconstriction in smooth muscle cells

A

Cause the release of intracellular calcium

25
Q

What are local factors

A

Substances produced as a result of metabolism

26
Q

Name local factors

A

Adenosine
Potassium
Carbon dioxide
Hydrogen ions

27
Q

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)

A

It will vasodilation to increase the blood flow.

28
Q

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

A

Active/ functional hyperaemia

29
Q

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

A

Reactive hyperaemia

30
Q

What is autoregulation

A

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

31
Q

Which organs have auto-regulation in their blood vessels

A

Kidney
Cerebral
Coronary circulation

32
Q

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

A

Vasodilation

33
Q

What happens when the arterial pressure falls past the lower limit

A

Autoregulation is lost

34
Q

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

A

Vasoconstriction occurs

35
Q

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

A

Auto regulation is lost

36
Q

What is the central neural mechanism of vessels

A

The control of blood vessels by the sympathetic nervous system

37
Q

Do blood vessels have parasympathetic innervation

A

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

38
Q

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

A

Vasoconstriction

39
Q

What does a decrease in the sympathetic activity cause

A

Vasodilation

40
Q

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

A

Noradrenaline

41
Q

Which receptors do noradrenaline act on in the blood vessels

A

Alpha 1 adrenoceptors

42
Q

What other receptor does noradrenaline bind weakly to on the arterioles

A

Beta 2 adrenoceptors

43
Q

What does circulating adrenaline cause

A

Vasodilation

44
Q

What receptor does circulating adrenaline bind to

A

Beta 2 receptors

45
Q

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

A

ADH

Angiotensin 2

46
Q

What does ADH cause

A

Vasoconstriction

47
Q

What does angiotensin 2 cause

A

Vasoconstriction

48
Q

When is angiotensin 2 produced

A

When the renal artery pressure falls

49
Q

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

A

Constriction of arterioles in multiple organs

50
Q

Give an example when reactive hyperaemia occurs

A

Weight lifting when there is no blood flow

51
Q

Which responce allows autoregulation

A

Myogenic responce

52
Q

What is the myogenic responce

A

When the walls are stretched and in response contract

53
Q

What receptors does noradrenaline bind to

A

Alpha 1 and beta 2 receptors

54
Q

What does circulating adrenaline cause to the blood vessel

A

Vasodilation

55
Q

What receptor does adrenaline act on

A

Beta 2

CVS (19 decks)

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