Systemic circulation

Question 1

blood volume

Answer 1

Systemic>pulmonary

veins> all else ( volume reservoirs, esp during hemorrhage)

Question 2

Blood pressure

Answer 2

Aorta>all else back to RA
Pressure drop at arterioles
Arteries are pressure reservoirs, maintain MAP (due to their elastic properties)

Question 3

MAP

Answer 3

averaged blood pressure (based on fluctuating pulse pressures) maintained by arteries

MAP=DBP+ 1/3 (SBP-DBP) AT REST

accounts for increased time spent in diastole (at rest)

MAP increases with exercise

Question 4

Fick principle

Answer 4

indirect method to determine blood flow rate (i.e. Q L/min)
Based on total O2 consumption and difference b/w arterial and venous O2

Q=VO2/Arterial-Venous O2 difference)

Question 5

blood flow velocity

Answer 5

Highest in aorta and lowest in capillaries

inversely related to CSA

measured by doppler ultrasound
flow velocity= flow/CSA

same volume passes thru each segment of aorta and capillaries per minute

Question 6

What leads to increased turbulence

Answer 6

• **1) Increased velocity (due to LOCAL decrease in diameter
  2) increased diameter
  3) decreased viscosity (anemia)

aorta likely develops turbulent flow first (largest diameter, increased flow rate)

Question 7

Compliance

Answer 7

index of distensibility of a vessel
=change in volume/change in pressure

veins are more compliant (i.e. distend more with an increase in volume)
decreases with age (increases pulse pressure on arterly)

Question 8

LaPlace’s Law (Wall stress)

Answer 8

measure of wall stress
—>increase radius=increases wall stress
Aorta has greatest wall tension–>higher risk for aneurysm
Capillaries have the lowest wall tension

Question 9

CO (Q) equation

Answer 9

=MAP/TPR

MAP=Pressure gradient=dP

Question 10

Driving force for blood flow

Answer 10

Base upon pressure GRADIENT

Not absolute numbers, the change in pressure determines blood flow

Question 11

Series resistance

Answer 11

flow is equal at all points (think segments of the circ system)

adding resistance increases overall resistance in system

total R is > individual resistance

Question 12

Parallel resistance

Answer 12

flow independently regulated
increased R=decreased overall systemic R

total R<individual R

allows you to regulate flow to meet tissue demands while maintaining MAP

Question 13

Blood Flow

Answer 13

directly related to pressure gradient
and radius^4th

inversely related to vessel length and blood viscosity

heavily influenced by SNS activation on a1 receptors–>VC

Question 14

autoregulation

Answer 14

flow independent of BP, proportional to metabolism and independent of nervous reflexes

esp in heart, brain, skeletal muscle, renal