Lecture 10 Blood Flow

Question 1

What are the three layers of the blood vessels?

Answer 1

1. Tunic Intima
   - Endothelium
2. Tunic media
   - Smooth muscle
   - controlled by sympathetic NS
3. Tunic externa
   - Mostly fibrous connective tissue (fibroblast/stem cells)

Question 2

List the major types of blood vessels from highest pressure to lowest pressure

Answer 2

1. Artery
2. Arterioles
3. Capillaries
4. Venule
5. Vein

Question 3

Which Vessels serve as pressure and volume reservoirs?

Answer 3

Large Arteries
Large Veins

Question 4

What is the Windkessel effect?

Answer 4

When large arterial bag expands (semilunar valve open), elastic characteristics hold energy which gained during ventricular ejection

Question 5

What happens after the arterial bag expands?

Answer 5

Elastic recoil of arteries moves blood forward during ventricular relaxation (semilunar valve closed)

Question 6

What do venules do?

Answer 6

Drain blood from capillaries into larger veins

Question 7

How do venules and veins differ from arteries?

Answer 7

Less smooth muscle and connective tissue

Question 8

How is backflow prevented when moving blood through the venous system?

Answer 8

Valves and series of connected bags help keep moving blood forward

Question 9

How much blood do veins hold?

Answer 9

70%
- act as a reservoir during hemorrhage

Question 10

What are the two types of vessels in capillary beds?

Answer 10

1. Arteriovenous Shunt
   - Connects arteriole to a venule (metarteriole)
2. True Capillaries
   - provide nutrient exchange (O2 and nutrients while removing CO2 and metabolic waste)
   - only 1 cell layer thick

Question 11

What determines blood fluid flow in a system?

Answer 11

• Directly proportional to the pressure gradient
  (High to Low) (depends on pressure gradient NOT absolute pressure)
• Inversely proportional to the resistance of the system

Question 12

Where is Blood Pressure the highest and lowest?

Answer 12

Highest: Aorta
Lowest: Venae Cavae

Question 13

What is Poiseuille’s Law?

Answer 13

• Resistance increases as length increases (relatively constant)
• Resistance increases as viscosity increases
  (relatively constant)
• Resistance decreases as radius increase (only meaningful variable)

Question 14

What happens if one vessel undergoes vasoconstriction?

Answer 14

• Blood volume does not change
• Other vessels not constricted must make up for the constricted one so that total flow is unchanged

Question 15

What are three factors that alter arteriolar resistance?

Answer 15

1. Myogenic “autoregulation”
2. Paracrines (local)
   - Active Hyperemia
   - Reactive Hyperemia
3. Sympathetic control
   - SNS: Norepinephrine
   - Adrenal medulla: epiniephrine

Question 16

What does Active Hyperemia do?

Answer 16

Locally mediated Increase in blood flow due to an increase in tissue metabolism

Question 17

What does Reactive Hyperemia do?

Answer 17

Locally mediated Increase in blood flow due to physical blockage (occlusion)

Question 18

How does Norepinephrine alter ateriolar diameter?

Answer 18

• Controlled release = slow vasoconstriction
• Rapid Release = High vasoconstriction
• Decreased release = Vasodilation

Question 19

What do GPCRs promote?

Answer 19

Calcium-mediated smooth muscle cell contraction without excitation-contraction coupling