Integration of Cardiovascular Mechanisms

Question 1

What are vascular smooth muscles controlled by?

Answer 1

Extrinsic and intrinsic mechanisms

Question 2

What is resistance to blood flow directly proportional to?

Answer 2

• blood viscosity

- length of blood vessel

Question 3

What is resistance to blood flow inversely proportional to?

Answer 3

Radius of blood vessel to the power 4

Question 4

What is resistance to blood flow mainly controlled by?

Answer 4

vascular smooth muscles through changes in the radius of arterioles

Question 5

When does adrenaline cause vasoconstriction?

Answer 5

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

Question 6

When does adrenaline cause vasodilation?

Answer 6

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

Question 7

What does adrenaline helps with?

Answer 7

Strategic redistribution of blood i.e during exercise

Question 8

What are important in intermediate control of blood pressure?

Answer 8

angiotensin II and antidiuretic- causes vasoconstriction

Question 9

What does extrinsic control act on?

Answer 9

Vascular smooth muscles - involves nerves and hormones

Question 10

What does intrinsic control do?

Answer 10

Match the blood flow of different tissues to their metabolic needs

Question 11

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

Answer 11

Intrinsic that over-ride extrinsic

Question 12

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

Answer 12

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

Question 13

What do local metabolic changes within an organ cause?

Answer 13

Contraction of arteriolar smooth muscles

Question 14

What are local humeral agents and what do they influence?

Answer 14

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

Question 15

What are local humeral agents released in response to?

Answer 15

tissue injury or inflammation

Question 16

What humeral agents cause vasodilation?

Answer 16

histamine
bradykinin
Nitric oxide

Question 17

What causes the activation of Nitric oxide synthase?

Answer 17

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

Question 18

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

Answer 18

cGMP- serves as second messenger for signalling smooth muscle relaxation

Question 19

What humeral agents cause vasoconstriction?

Answer 19

Serotonin
Thromboxane A2
Leukotrienes
endothelin

Question 20

What is endothelin?

Answer 20

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

Question 21

How is endothelial damage/disfuntion caused?

Answer 21

high blood pressure, high cholesterol, diabetes and smoking

Question 22

What are endothelial produced vasodilators?

Answer 22

anti-thrombotic
anti-inflammatory
anti-oxidants

Question 23

What are endothelial produced vasoconstrictors?

Answer 23

pro-thrombotic
pro-inflammitory
pro-oxidants

Question 24

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

Answer 24

cold- vasoconstriction

warmth- vasodilatation

Question 25

What happens in a myogenic response?

Answer 25

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

Question 26

What does dilatation of arterioles cause?

Answer 26

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

Question 27

What 4 factors increase venous return?

Answer 27

increasing:

• venomotor tone
• skeletal muscle pump
• blood volume
• respiratory pump

Question 28

What impact does an increased venous return have?

Answer 28

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

Question 29

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

Answer 29

sympathetic nerve fibres and stimulation causes venous contriction

Question 30

What does increased venomotor tone cause?

Answer 30

Increased venous return , SV and MAP

Question 31

what allows blood to move forward towards the heart?

Answer 31

One-way venous valves

Question 32

During exercise, what increases and what does this cause?

Answer 32

Sympathetic nerve activity increases which increase HR and SV and so CO

Question 33

How is flow reduced to kidneys and gut during exercise?

Answer 33

sympathetic vasomotor nerves cause vasoconstriction

Question 34

How is flow increased to skeletal and cardiac muscle during exercise?

Answer 34

Metabolic hyperaemia overcomes vasomotor drive and causes vasodilatation

Question 35

What does metabolic hyperaemia decrease?

Answer 35

TPR and DBP