Circulation 6

Question 1

What are the resistance vessels?

Answer 1

Arterioles
Precapillary sphincters
Metarterioles
Venous resistance

Question 2

For what aspects of circulation is vascular smooth muscle responsible?

Answer 2

Control of total peripheral resistance
Arterial and venous tone
Distribution of blood flow through the body

Question 3

Global control mechanisms

Answer 3

Neural and hormonal

Question 4

Local control mechanisms

Answer 4

Myogenic
Metabolic
Endothelial
Mechanical

Question 5

Autoregulation

Answer 5

The intrinsic property of an organ or tissue to maintain constant blood flow deespite changes in arterial perfusion pressure (due to gravity)

Question 6

When does autoregulation fail?

Answer 6

At very high or very low pressures

Question 7

Myogenic hypothesis

Answer 7

Vascular smooth muscle contracts in response to stretch and relaxes in response to a reduction in stretch

Question 8

Result of the myogenic response during increase in pressure

Answer 8

Causes a stretch of the vascular wall, which causes the vascular smooth muscle to contract, which results in an increase in resistance and a decrease in flow

Question 9

Result of myogenic response during a decrease in pressure

Answer 9

Reduction of stretch of the vessel wall, allowing the muscles to relax, reducing resistance and increasing flow

Question 10

Metabolic hypothesis

Answer 10

Metabolic activity produces substances that relax vascular smooth muscle (CO2, H+, adenosine)

Question 11

What happens with the metabolites as pressure increases?

Answer 11

There is a brief increase in blood flow when there is increased pressure, which picks up the metabolites and then allows the vessels to constrict, which then decreases flow and increases resistance

Question 12

What happens with metabolites as pressure decreases?

Answer 12

The metabolites build up due to decreased blood flow, which then causes vessels to dilate, resistance to decrease, and flow to increase

Question 13

Organs with strong autoregulation

Answer 13

Heart, brain, kidney, skeletal muscle

Question 14

Organs with weak autoregulation

Answer 14

Splanchnic circulation

Question 15

Organs with little autoregulation

Answer 15

Skin, lungs

Question 16

Is autoregulation dependent upon the endothelium?

Answer 16

No

Question 17

For what response is the endothelium responsible?

Answer 17

Endothelial-mediated mechanism (release of EDRF or NO)

Question 18

Endothelial-derived agents

Answer 18

Vasodilators: EDRF, NO, prostacyclin
Vasoconstrictors: ET

Question 19

Active (functional) hyperemia

Answer 19

Increased blood flow caused by enhanced tissue activity

Question 20

Possible factors in active hyperemia

Answer 20

Potassium ion, inorganic phosphate, interstitial osmolarity

Question 21

Reactive hyperemia

Answer 21

Transient increase of blood flow that follows a brief arterial occlusion

Question 22

Mechanical augmentation

Answer 22

An increase in tissue pressure can mechanically compress small vessels and alter blood flow

Question 23

Possible causes of mechanical augmentation

Answer 23

Muscular contraction (heart, muscle)
Alveolar pressure 
Tumors (venous constriction/obstruction)