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555- Physiology & Pathophysilogy > Exam 7 - Biophysics / Vessels > Flashcards

Exam 7 - Biophysics / Vessels Flashcards

1
Q

Basic principles of circulatory function

A
  • Rate of blood flow to each tissue is controlled based on need
    ~ local control by arterioles
    ~ CNS and hormones can control in emergencies
    ~ if metabolic need increases…blood flow increases
  • CO is controlled by sum of all local tissue flows
    ~ Venous return determines CO automatically (starlings curve)
    ~ CNS can help in emergencies
  • Art. pressure regulation is independent of local blood flow and CO
    ~ this allows to change flow in localized regions
    ~ controlled by sensor feedback systems and kidneys
    ~ If pressure falls: Increase contractility
    Constrict large veins (move volume to arteries)
    Constrict arterioles (hold more volume in arteries)
    Kidneys hold onto more volume…increase CO
    (First 3 happen quickly…kidneys take time)
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2
Q

Ohm’s law

A
  • dP = Q x R
  • Flow is same for vessels in series
  • Pressure drop determined by change in resistance
  • Smaller the vessel…higher the velocity
  • Smaller the vessel….higher the pressure drop
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3
Q

Reynold’s number

A
  • tendency for turbulence to occur
  • velocity in vessel is faster in center….no flow at boundary
  • Shear Stress: force on wall by moving blood…wants to pull wall w/ it
    ~goes up with viscosity / flow
    ~goes down increase in radius by factor of 3
  • turbulent flow increases resistance and damage to cells
  • AS or AI can create turbulent flow (each have unique murmur)
  • Re = (velocity x diameter x density) / (viscosity)
  • Turbulence in straight tube at 2000….side branches at 200-400
    - decrease due to radius and venturi effect
  • will get turbulence in aorta….very seldom in smaller arteries
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4
Q

Poiseuille’s Law

A
  • Shows factors that affect resistance to flow in system
  • diameter has greatest effect on flow (factor of 4)
  • arterioles can cause BIG changes in flow with SMALL changes in d
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5
Q

Vessels in parallel

A
  • Flow in = Flow out
  • Flow doesn’t have to be same through each vessel
  • Total R across network is smaller than R for any one vessel
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6
Q

Bruits

A
  • vibration you can feel caused by flow
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7
Q

Murmur

A
  • sound caused by flow
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8
Q

What can change viscosity of blood

A
  • Temperature (inverse)
  • [ Plasma protein ] (direct)
  • [ RBC ] (direct)
  • Shear stress (direct)
  • Blood flow (inverse)
  • Blood is 3x more viscous than water
  • Can be a problem in capillaries… capillary sludging…especially cold
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9
Q

Viscosity on bypass

A
  • dilute plasma proteins (V goes down)
  • Dilute RBC (V goes down)
  • Cool patient (V goes up)
  • Give vasoconstrictor (V goes up potentially) (careful at cool temps)
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10
Q

Systemic circulation

A
  • Peripheral circulation
  • maintains constant internal environment in 3rd space
  • sophisticated irrigation system
    ~ gets nutrients and removes wastes when needed
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11
Q

Pulmonary circulation

A
  • Brings blood flow in contact w/ resp mem of lungs
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12
Q

Arteries

A
  • transport blood at high pressure
  • elastic / strong walls
  • not muscular
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13
Q

Arterioles

A
  • controlled by ANS
  • meta arterioles and pre cap sphincters really control local flow
  • control flow through capillary bed
  • strong / muscular walls….can contract all the way closed
  • can dilate with 7x increase in radius
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14
Q

Capillaries

A
  • all exchange here
  • very thin with gaps between cells (cap pores)
    ~ pores very permeable to water / Na / K / Cl / glucose
  • O2 / CO2 / ethanol move directly across cells
  • proteins stay inside
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15
Q

Endothelial cells

A
  • line entire CV system including heart and valves
  • control transcapillary solute and water exchange
  • active tissue: alive / interact / respond
    ~ aid/inhibit coagulation
    ~ affect function of platelets and neutrophils
    ~ major role in perfusion injury
    ~ interact w/ plasma proteins and activate them
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16
Q

Transcapillary fluid movement

A
  • Filtarion = out of capillary / more at arterial end
  • absorption = in / more at venous end
  • overall net filtration
  • Hydrostatic Cap pressure (push out) = 20-25
  • Hydrostatic interstitial pressure (push in) = -3
  • Osmotic Cap pressure (pull in) = 28
  • Osmotic interstitial pressure (pull out) = 8
17
Q

Lymphatic system

A
  • path for excess i fluid and proteins to return to circ system
  • flushes bacteria and other foreigners out of i fluid into nodes
  • same size / more porous than capillaries / less numerous
  • one way valves
  • return to blood near right side of heart
  • 2.5 L returned each day
18
Q

Venules

A
  • collect blood from capillaries
  • direct blood to veins
  • capacitance vessel (store blood)
19
Q

Veins

A
  • transport blood at low pressure
  • thin walls / valves
  • velocity greater than caps but lower than arteries
  • shift blood to arteries when needed (capacitance vessel)
  • Peripheral veins: veins outside thorax
  • Central veins: major veins in thorax
    ~ affected by thoracic pressure
    ~ lowest pressure in vascular system
    ~ determine ventricular filling
20
Q

Aorta specs

A 
ID = 2.5 cm
Thick = 2 mm
# = 1
X-sectional = 4.5 cm^2
21
Q

Arterioles specs

A 
ID = 30 um
Thick = 20 um
# = 50,000,000 or 5x10^7
X-sectional = 400 cm^2
22
Q

Capillaries specs

A 
ID = 5 um
Thick = 1 um
# = 10^10
X-sectional = 4500 cm^2
23
Q

Vena CAva specs

A 
ID = 3 cm
Thick = 1.5 mm
# = 2
X-sectional = 18 cm^2
24
Q

Blood volume distribution

A 
Arteries - 13%
Arterioles/Caps - 7%
Veins/venules/sinus - 64%
    - Systemic Circ = 84%
- Heart = 7%
- Pulmonary Circ = 9%
25
Q

Circ system facts

A
  • Flow highest in Arteries/arterioles (500 mm/s)
  • Flow lowest in Caps (0.5 mm/s)
  • Most blood volume in veins and venules (64%)
  • Pressure highest in Arts/arterioles (mean 100) (pulsatile flow)
  • Pressure lowest in Caps (25) (stop pulsatile flow)
  • Highest resistance in arterioles
  • Pulmonary pressure much lower than systemic pressure
26
Q

Mean Arterial Pressure

A
  • constant even if pulse pressure widens
  • not changed by over/under dampening
    MAP = (COxTPR) + CVP
    - any change in CO or SVR will change MAP
    Or MAP = PD + (1/3 x Pulse pressure)
  • MAP is closer to PD than PS i normal conditions
    - If HR goes up….MAP closer to PS
  • MAP goes up with age: Decrease in distensibility
    Increase in SVR
    Changes in control mechanisms
27
Q

Relationship of CO / Pre-load / Venous return

A
  • Increase in VR increases the rest
  • Changing diameter of artery/vein does not change SVR/Flow
    ~ they are elastic / dispensable / compliant
    - Vein elasticity helps move blood in/out of arteries (VR)
    - Artery elasticity helps with ejection of blood into aorta
    ~ Arterioles are what change flow/SVR
28
Q

Distensibility

A

= (dV) / (dP x original V)

  • % change in vol. per 1 mmHg change in pressure
  • Veins 8x more distensible than arteries (so thin)
    ~same increase in pressure would lead to 8x increase in volume
  • Pulmonary arteries 6x more distensible than systemic arteries
  • Pulmonary and systemic veins are the same (8x more than syst art)
29
Q

Compliance

A

= dV / dP

  • Distensibility x initial volume
  • systemic veins 24x more compliant than systemic arteries
    ~ 8x more distensible / hold 3x the volume
  • Volume-pressure curves show compliance
30
Q

Volume-Pressure Curves

A
  • Inverse of line slope is Compliance
  • High compliance is good / Low is bad
  • Arterial: Normal compliance = 2 ml/mmHg
    Normal 700 ml = 100 mmHg mean pressure
    Drop to 400 ml = 0 mmHg
    Small change in volume = big change in pressure
    - Arteries help heart generate pressure
  • Venous: Normal compliance = 100 ml/mmHg
    Normal volumes = 2000-3500 mls
    Normal pressure = 0-20 mmHg
    Large change in volume = small change in pressure
  • Sympathetic tone shifts curves up and left - bigger slopes
    - decreased compliance
    - shifts volume from one compartment to another
    - increases venous return
  • Decrease sympathetic tone - dilates…pressure drops
    - increased compliance
    - holds volume in compartment
31
Q

Stress-Relaxation of vessels

A
  • Response to volume changes
  • No ANS innervation…..all innate to vessels
  • Vessels will dilate/constrict to keep BP normal
    - sometimes can’t 100% compensate
    - increase vol cause relax….decrease vol cause constrict
    - hemorrhage is example (will cause constriction)
32
Q

Arterial pulse

A
  • Distensibility allows aorta to accept ejected blood w/o huge increase in pressure
  • Energy put into stretching aorta is given back in diastole to push blood through vascular tree….w/o stretch…pressure would be 0 once ejection ends
  • Pressure pulse is faster than flow pulse due to inertia in aorta
    • flow must overcome inertia of blood already in aorta
  • Compliance goes down as you move down tree (rate goes up)
    - higher compliance = lower transmission rate
  • In aorta…pressure wave is 15x faster than actual flow of blood
33
Q

Normal SV

A

60-100 mls

34
Q

Pulse Pressre

A

= Ps - Pd
= SV / arterial compliance (if all SV stay in aorta during ejection)
- widens as you move down tree… lower comp
- Stronger contractions will increase pulse pressure
- Pp increases with age due to big drop in arterial compliance

35
Q

Interpretation of blood pressure

A
  • systolic and diastolic pressure alone not good estimators
  • systolic and diastolic are affected by more than just SVR
    - HR / SV / PP
  • Better to look at MAP and arterial pulse pressure
36
Q

Right atrial pressure (CVP)

A
  • normally 0 (range: -5 to +30)
  • Balance of ability of R heart to pump AND blood return to RA
  • Decreased by: increase contractility (more blood pumped out)
    Decrease venous return
    - low volume/low venous tone/constrict arterioles
  • Increased by: decrease contractility / high VR
  • Normally heart can compensate for VR and CVP change is minimal
37
Q

Venous resistance

A
  • Periph venous pressure usually 4-6 mmHg higher than CVP
    • due to collapse of veins entering thorax
    • CVP must rise this amount before you see increase in peripheral venous pressure
  • Intra-abdominal pressure can rise to 15-30 if:
    - pregnant / tumors / obesity / ascites (fluid build up)
38
Q

Effect of gravity on venous pressure

A
  • When standing, CVP is close to 0 because heart pumps out excess blood
  • Everything below heart is higher
  • Pressure in feet 90 mmHg IF standing still
    - movement helps keep this lower (usually around 20 if standing)
    - can lose 10-20% of CBV in 15-30 min if standing still
  • Neck is 0 because atmospheric pressure collapses veins
  • Theoretical 10 mmHg lower in brain due to gravity
  • One way valves help fight gravity too
39
Q

Blood reservoirs

A
  • some organs can hold onto blood and put into CBV if needed
  • Spleen: 100 mls
  • Liver: several hundred mls
  • Abdominal veins: 300 mls
  • Venous plexus: several hundred mls
  • Heart: 50-100 mls (drops in sympathetic stimulation)
  • Lungs: 100-200 mls

555- Physiology & Pathophysilogy (12 decks)

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