Part II: The Systemic Circulation

Question 1

Define transmural pressure

Answer 1

pressure tending to distend (or collapse) a vessel

Question 2

Define mean arterial pressure

Answer 2

average pressure existing in the aorta and proximal arterial system during one cardiac cycle

Question 3

What is the formula for mean arterial pressure?

Answer 3

diastolic pressure + 1/3 pulse pressure

Question 4

Name the two physiological factors responsible for determining mean arterial pressure

Answer 4

1) cardiac output

2) peripheral resistance (responsible for pressurizing the system)

Question 5

Name the two physical factors that determine mean arterial pressure

Answer 5

1) arterial blood volume

2) arterial compliance

Question 6

Of the two physiological factors determining MAP, which primarily affects SYSTOLIC pressure?

Answer 6

cardiac output

regulated by autonomic nervous system

Question 7

Of the two physiological factors determining MAP, which primarily affects DIASTOLIC pressure?

Answer 7

peripheral resistance

also regulated by ANS but local regulation can override nervous control

Question 8

What is responsible for maintaining arterial blood pressure moment to moment via the ANS?

Answer 8

baroreceptor reflex

Question 9

What happens to pulse pressure as you exercise and what is responsible for that change?

Answer 9

It widens because the systolic pressure increases and diastolic stays the same

Question 10

What happens to mean arterial pressure as you exercise?

Answer 10

it increases

Question 11

Name a few diseases that decrease blood pressure?

Answer 11

1) congestive heart failure
2) infarction
3) bradycardia
4) sepsis

Question 12

What does arterial compliance affect? Systolic or diastolic pressure?

Answer 12

Both! Inversely related to systolic (decrease compliance, increase systolic) and directly related to diastolic

Question 13

What factors can alter arterial compliance?

Answer 13

age, blood volume, sympathetic tone, pregnancy

Question 14

Do highly compliant vessels have a larger or small pulse pressure?

Answer 14

SMALL

the lower the compliance, the higher the systolic so that generates a larger pulse pressure

Question 15

What are the 3 mechanisms of local control on peripheral resistance?

Answer 15

1) Myogenic response
2) endothelium-mediated regulation (EDRF, NO, endothelin)
3) local metabolic changes (O2, CO2, metabolites)

Question 16

What are the 3 global mechanisms of modulating peripheral resistance?

Answer 16

1) baroreceptor reflex
2) hormonal effects
3) sympathetic activity

Question 17

What effect does the sympathetic system have on blood vessel diameter?

Answer 17

vasoconstrict

increasing venous return in the veins and total peripheral resistance in the arteries

Question 18

What role does the sympathetic system play during exercise?

Answer 18

1) increases heart rate
2) increases contractility of the heart

OVERALL INCREASES CARDIAC OUTPUT

Question 19

What three sections of the body are unaffected by sympathetic vasoconstriction?

Answer 19

1) cerebral
2) pulmonic
3) cardiac

there are no alpha receptors there to receive input

Question 20

What molecules are involved in metabolic vasodilation?

Answer 20

1) K+
2) adenosine
3) CO2
4) H+

Question 21

What is the importance of metabolic vasodilation?

Answer 21

It is what allows both skeletal muscle AND the heart to vasodilate during exercise. This lowers vascular resistance to these areas and increases blood flow 15-20 fold

Question 22

How does metabolic vasodilation actually occur if there is sympathetic tone going on in the background, vasoconstricting arteries?

Answer 22

because local mechanisms ALWAYS override global, hormonal/neural input

Question 23

How do the heart and skeletal muscle ensure increased oxygen flow during exercise?

Answer 23

Skeletal muscle can pull more O2 from hemoglobin (myoglobin has stronger affinity)

Heart can only get more O2 by increasing blood flow to it. It CANNOT increase O2 extraction during exercise

Question 24

What happens to venous return during exercise?

Answer 24

It increases because of venoconstriction (want to get more blood back to the heart)

Question 25

What happens to systolic pressure as you exercise?

Answer 25

It sharply goes up, primarily because of the increase in stroke volume

(also causes pulse pressure to increase)