HUBS192 Lecture 11 - Controlling Regional Bloodflow

Question 1

what is the quote that explains why it is important for mean arterial blood pressure to be maintained?

Answer 1

“maintenance of arterial blood pressure at a constant level by a central control mechanism allows each organ or region to control its own perfusion…sufficient to meet its own metabolic needs”

Question 2

what is the relationship between high pressure and control of flow?

Answer 2

high pressure allows for the full control of flow in different directions
-high pressure needs to be maintained for this to occur

Question 3

what is the design of systemic circulation?

Answer 3

parallel design where cardiac output is distributed to all organs

Question 4

what are the 2 features of the parallel design of the systemic circulation?

Answer 4

1) continual branching of arterial network

2) divides blood flow among the regional (organ) circulations and then goes back to the heart

Question 5

what is the pressure in systemic circuit?

Answer 5

high pressure to drive unidirectional blood flow

Question 6

what is the pressure in the pulmonary circuit?

Answer 6

low pressure with low resistance

Question 7

what is the distribution of cardiac output at rest for the 7 organ types?

Answer 7

• large cardiac output to the kidneys, abdominal viscera, brain and skeletal muscle
• less cardiac output to the skin and other tissues

Question 8

what are the 7 organ types involved in the cardiac output during exercise?

Answer 8

1) brain
2) kidneys
3) abdominal viscera
4) skin
5) other tissues
6) skeletal muscles
7) heart

Question 9

what is the distribution of cardiac output during light and heavy exercise?

Answer 9

• cardiac output of the brain is maintained at the same level as at rest because the demand for the brain function is always constant
• increased cardiac output to the skeletal muscle, skin and the heart (highly increased flow to these places)
• decreased cardiac output compared to at rest from the kidneys, abdominal viscera, other tissues and GI tract

Question 10

what happens when we exercise to the cardiac output distribution to our organs?

Answer 10

when we exercise it activates our sympathetic nervous system response of fight or flight whereas at rest the parasympathetic nervous system is activated (rest and digest) therefore during exercise we are moving resources (blood) towards our heart and muscles and moving resources (blood) away from organs involved with rest and digest as it is no longer required

Question 11

what helps to make the cardiac output system work?

Answer 11

the ability to determine where the blood is flowing through divergent flow depending on metabolic demands

Question 12

where is blood flow increased to during exercise?

Answer 12

• skeletal muscle
• heart
• skin

Question 13

where is blood flow decreased to during exercise?

Answer 13

• GI tract
• kidneys
• other tissues
• abdominal viscera

Question 14

where is blood flow constant to during exercise?

Answer 14

-brain

Question 15

what are the 3 components of systemic circulation during exercise?

Answer 15

• increased cardiac output (CO)
• constant mean arterial blood pressure (MAP)
• decreased total peripheral resistance (TPR)

Question 16

what is the relationship between total peripheral resistance (TPR) and cardiac output during exercise?

Answer 16

TPR is decreased during exercise to allow for a greater blood flow and this increases cardiac output

Question 17

what is the resistance involved in controlling regional blood flow in the individual circulation of muscle?

Answer 17

increased flow results from decreased resistance

Question 18

what is the resistance involved in controlling regional blood flow in the individual circulations of kidneys?

Answer 18

decreased flow results from increased resistance

Question 19

what are arterioles?

Answer 19

small vessels that lead into the capillaries surrounded by smooth muscle

Question 20

what are the function of arterioles?

Answer 20

to determine blood flow “in” and blood flow “out”

Question 21

what is the equation for resistance (R)?

Answer 21

R=1/r^4

Question 22

what is the radius of a vessel?

Answer 22

half of the diameter from the centre point of the vessel

Question 23

what is the relationship between a change luminal diameter and resistance?

Answer 23

a small change will cause a HUGE change in resistance to flow

Question 24

what is the rule of 16?

Answer 24

if the luminal diameter is changed by a factor of 2 then the resistance will change by a factor of 16

Question 25

how is blood flow than organ or region controlled?

Answer 25

controlled by adjusting arteriolar (‘vascular’) tone and radius

Question 26

what is the relationship between smooth muscle and a vessel associated with exercise?

Answer 26

the smooth muscle surrounding the vessel relaxes allowing the vessel to expand=vasodilation
-doubles the radius means the resistance is decreased by 16 which means flow is increased by 16 times (16x16=256mL per minute)

Question 27

what is the relationship between smooth muscle and a vessel not associated with exercise?

Answer 27

the smooth muscle surrounding the vessel contracts constricting the size of the vessel=vasoconstriction
-halves the radius means the resistance is increased by 16 which means flow is decreased by 16 times (16/16=1mL per minute)

Question 28

what are the 3 main ways that control vascular resistance?

Answer 28

1) mechanical (response to force) through a local signal
2) neural systems through central signal
3) humoral (blood) through central signal

Question 29

what is the relationship between fine vascular control and arterial blood pressure?

Answer 29

fine vascular control by an organ depends on a sufficiently high arterial blood pressure