Systemic Circulation

Question 1

three axes of pressure

Answer 1

• hydrostatic
• driving
• transmural

Question 2

compliance

Answer 2

• in BV, greater volume means greater fluid
• infinite compliance can hold as much as possible
• BV are finite
• deltaV/deltaPtm (Ptm=Pin-Pout)
• elastance 1/C
• pay attention to the graph

Question 3

arterial and venous compliance

Answer 3

• veins much more compliant
• arteries relatively linear relationship over 0-200 mm Hg pressure
• veins steep relationship up to 50 mm Hg
• compliance in veins low above physiological pressures-only get there via graft

Question 4

pressure vs volume

Answer 4

• elastance curve
• steeper means less compliant, flatter means more compliant
• SNS can shift both to left
• in arteries, if volume drops even a little, pressure dives

Question 5

vascular compliance and age

Answer 5

• decreases with age

- slope of volume vs. pressure goes down (pressure vs volume would go up)

Question 6

conversion to steady flow

Answer 6

• glass vs rubber- steady flow pressure and flow are steady
• when pulsing- non compliant glass has severe stops and starts in pressure and output
• rubber has bounding line- pressure drives flow and vessel out so even when there isn’t flow from spigot there is still flow into glass- same as aorta
• windkessel model

Question 7

aortic pulse contour

Answer 7

• pulse pressure is directly proportional to SV and inversely related to compliance
• diastolic pressure never drops too low because then couldn’t perfuse heart

Question 8

pressure tension on BV walls

Answer 8

• tension is proportional to transmural pressure and radius

- tension is force per unit length in dynes/cm

Question 9

elasticity and resistance

Answer 9

• makes resistance and pressure inversely proportional
• increase pressure in BV and decrease resistance
• when total body pressure drops, TPR increases to maintain CO

Question 10

elasticity and flow

Answer 10

• sort of directly proportional
• flow increases with pressure
• but there is a critical closing pressure when the vessel will collapse- also why we need a diastolic pressure

Question 11

hemorrhagic shock

Answer 11

• shifts critical closing pressure to the right**
• shifts elastance curves to the left
• in arteries this means you can maintain pressure at lower volume
• in veins can mobilize blood

Question 12

raynauds syndrome

Answer 12

• shifts resistance vs pressure to the right in the cold

- shifts flow vs pressure to the right, moves critical closing pressure- constricted