Lecture 10 Blood Flow Flashcards
What are the three layers of the blood vessels?
- Tunic Intima
- Endothelium - Tunic media
- Smooth muscle
- controlled by sympathetic NS - Tunic externa
- Mostly fibrous connective tissue (fibroblast/stem cells)
List the major types of blood vessels from highest pressure to lowest pressure
- Artery
- Arterioles
- Capillaries
- Venule
- Vein
Which Vessels serve as pressure and volume reservoirs?
Large Arteries
Large Veins
What is the Windkessel effect?
When large arterial bag expands (semilunar valve open), elastic characteristics hold energy which gained during ventricular ejection
What happens after the arterial bag expands?
Elastic recoil of arteries moves blood forward during ventricular relaxation (semilunar valve closed)
What do venules do?
Drain blood from capillaries into larger veins
How do venules and veins differ from arteries?
Less smooth muscle and connective tissue
How is backflow prevented when moving blood through the venous system?
Valves and series of connected bags help keep moving blood forward
How much blood do veins hold?
70%
- act as a reservoir during hemorrhage
What are the two types of vessels in capillary beds?
- Arteriovenous Shunt
- Connects arteriole to a venule (metarteriole) - True Capillaries
- provide nutrient exchange (O2 and nutrients while removing CO2 and metabolic waste)
- only 1 cell layer thick
What determines blood fluid flow in a system?
- Directly proportional to the pressure gradient
(High to Low) (depends on pressure gradient NOT absolute pressure) - Inversely proportional to the resistance of the system
Where is Blood Pressure the highest and lowest?
Highest: Aorta
Lowest: Venae Cavae
What is Poiseuille’s Law?
- Resistance increases as length increases (relatively constant)
- Resistance increases as viscosity increases
(relatively constant) - Resistance decreases as radius increase (only meaningful variable)
What happens if one vessel undergoes vasoconstriction?
- Blood volume does not change
- Other vessels not constricted must make up for the constricted one so that total flow is unchanged
What are three factors that alter arteriolar resistance?
- Myogenic “autoregulation”
- Paracrines (local)
- Active Hyperemia
- Reactive Hyperemia - Sympathetic control
- SNS: Norepinephrine
- Adrenal medulla: epiniephrine
What does Active Hyperemia do?
Locally mediated Increase in blood flow due to an increase in tissue metabolism
What does Reactive Hyperemia do?
Locally mediated Increase in blood flow due to physical blockage (occlusion)
How does Norepinephrine alter ateriolar diameter?
- Controlled release = slow vasoconstriction
- Rapid Release = High vasoconstriction
- Decreased release = Vasodilation
What do GPCRs promote?
Calcium-mediated smooth muscle cell contraction without excitation-contraction coupling
