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Flashcards in Integration of Cardiovascular Mechanisms Deck (35)
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1

What are vascular smooth muscles controlled by?

Extrinsic and intrinsic mechanisms

2

What is resistance to blood flow directly proportional to?

-blood viscosity
-length of blood vessel

3

What is resistance to blood flow inversely proportional to?

Radius of blood vessel to the power 4

4

What is resistance to blood flow mainly controlled by?

vascular smooth muscles through changes in the radius of arterioles

5

When does adrenaline cause vasoconstriction?

When acting on alpha receptors ( predominant in skin, gut, kidney arterioles)

6

When does adrenaline cause vasodilation?

When acting on Beeta 2 receptors (predominate in cardiac and skeletal muscles arterioles)

7

What does adrenaline helps with?

Strategic redistribution of blood i.e during exercise

8

What are important in intermediate control of blood pressure?

angiotensin II and antidiuretic- causes vasoconstriction

9

What does extrinsic control act on?

Vascular smooth muscles - involves nerves and hormones

10

What does intrinsic control do?

Match the blood flow of different tissues to their metabolic needs

11

what control has the ability to over-ride the other?

Intrinsic that over-ride extrinsic

12

What factors causes relaxation of arteriolar smooth muscles resulting in vasodilation and metabolic hyperaemia?

Decreased local PO2
Increased local PCO2
Increased local [H+] (decreased pH)
Increased extra-cellular [K+]
Increased osmolality of ECF
Adenosine release (from ATP)

13

What do local metabolic changes within an organ cause?

Contraction of arteriolar smooth muscles

14

What are local humeral agents and what do they influence?

Local chemicals released within an organ and influence the contraction of arterial and arteriolar smooth muscles

15

What are local humeral agents released in response to?

tissue injury or inflammation

16

What humeral agents cause vasodilation?

histamine
bradykinin
Nitric oxide

17

What causes the activation of Nitric oxide synthase?

shear stress on vascular endothelium as a result of increased blood flow

18

What does the diffusion of NO into smooth muscle cells activate the formation of?

cGMP- serves as second messenger for signalling smooth muscle relaxation

19

What humeral agents cause vasoconstriction?

Serotonin
Thromboxane A2
Leukotrienes
endothelin

20

What is endothelin?

potent vasoconstrictor released from endothelial cells. Its production is stimulated by various agents which cause vasoconstriction

21

How is endothelial damage/disfuntion caused?

high blood pressure, high cholesterol, diabetes and smoking

22

What are endothelial produced vasodilators?

anti-thrombotic
anti-inflammatory
anti-oxidants

23

What are endothelial produced vasoconstrictors?

pro-thrombotic
pro-inflammitory
pro-oxidants

24

What are the effects of cold and warmth on vascular smooth muscles?

cold- vasoconstriction
warmth- vasodilatation

25

What happens in a myogenic response?

-If MAP rises resistance vessels automatically constrict to limit flow
-If MAP falls resistance vessels automatically dilate to increase flow

26

What does dilatation of arterioles cause?

sheer stress in the arteries upstream to make them dilate and this increases blood flow to metabolically to active tissues

27

What 4 factors increase venous return?

increasing:
-venomotor tone
-skeletal muscle pump
-blood volume
-respiratory pump

28

What impact does an increased venous return have?

increase in atrial pressure --> increased EDV -->stroke volume

29

What are venous smooth muscles supplied with and what does stimulation cause?

sympathetic nerve fibres and stimulation causes venous contriction

30

What does increased venomotor tone cause?

Increased venous return , SV and MAP