Hemodynamics (Exam 1)

Question 1

Blood Vessels: Flow of blood, tunics (3)

Answer 1

• Arteries > Arterioles > Capillaries > Venules > Veins
• Three tunics:
  
  • Tunica interna (intima) - simple squamous (endothelium)
    
    • very thin
  • Tunica media - smooth muscle and elastic fibers - vasoconstriction/vasodilation
    
    • much thicker in arteries than in veins
  • Tunica externa - elastic and collagen fibers

Question 2

Arteries: Overview

Answer 2

• Vasoconstriction/vasodilation
• Elastic arteries (Pressure reservoir)
  
  • closest to heart
    
    • Elastic fibers
• Muscular arteries (Distributing arteries)
  
  • More smooth muscle = more control
• Anastomosis
  
  • 2 or more arteries to tissues
  • Collateral circulation

Question 3

Capillaries: definition (2 words), function

Answer 3

• Single layer of endothelium and basement membrane
• Exchange vessels
• Microcirculation = flow from arterioles > capillaries > veins
• Capillary bed = 10-100 capillary network (precapillary sphincters control flow

Question 4

Blood Distribution: Percentages

Answer 4

• Blood reservoirs = systemic veins and venules (64%)
  
  • Blood can be diverted if needed (venoconstriction)
• Remainder:
  
  • 13% = systemic arteries/arterioles
  • 9% = pulmonary blood vessels
  • 7% = heart
  • 7% = systemic caps.

Question 5

Capillary Exchange: definition, methods (3)

Answer 5

• Movement of substances between blood and interstitial fluid
• Accomplished by:
  
  • Simple diffusion - passive transport through fenestrations or endothelial cells
  • Transcytosis - useful for large, lipid-insoluble substances
  • Bulk flow

Question 6

Bulk Flow: definition and functions

Answer 6

• Movement of large numbers of substance at faster rate
• Regulates relative volumes of blood and interstitial fluid
• Pressure driven
• Filtration and Reabsorption

Question 7

Filtration: definition and causes

Answer 7

• Bulk flow from capillaries into interstitial fluid
• Promoted by:
  
  • Blood hydrostatic pressure (BHP) (Interstitial fluid hydrostatic pressure (IFHP) negligible)
    
    • Fluid pushing out from walls of capillaries. Higher BHP = more fluid expelled
  • Interstitial fluid osmotic pressure (IFOP)
    
    • osmotic pressure - draw fluid into area

Question 8

Reabsorption: denition and causes

Answer 8

• Bulk flow from interstitial to capillaries
• Promoted by:
  
  • Blood colloid osmotic pressure (BCOP) - caused by plasma proteins
    
    • main factor in reabsorption
  • Again, IFHP close to zero

Question 9

Starling’s Law of the Capillaries

Answer 9

• Near equilibrium of filtration and reabsorption volumes
• Net filtration pressure
  
  • NFP = (BHP+IFOP) - (BCOP + IFHP)
    
    • (BHP+IFOP) = Filtration
    • (BCOP+IFHP) = Reabsorption
  • +NFP = net filtration (arterial end)
  • -NFP = net reabsorption (venous end)

Question 10

Edema: Defintion and causes (3)

Answer 10

• Filtration >> Reabsorption
• Due to:
  
  • Increased capillary BP (high BHP)
  • Increased capillary permeability
  • Decreased concentration of plasma proteins (low BCOP)

Question 11

Blood flow: definition and causes (3)

Answer 11

• Volume of blood in tissue over time (mL/min)
• Influenced by:
  
  • Cardiac output (HR and SV)
  • Pressure difference between areas (Pressure gradient)
    
    • gradient = high to low
  • Resistance in vessels
    
    • increase = less blood flow

Question 12

Blood Pressure: definition, characterisitics, equations (MAP and Pulse Pressure)

Answer 12

• Hydrostatic pressure exerted by blood on vessel walls
  
  • Systolic BP = highest arterial pressure during systole
  • Diastolic BP = lowest arterial pressure during diastole
• Decreases w/ distance
• MAP = diastolic + 1/3 (systolic-diastolic)
  
  • Mean Arterial Pressure
• Pulse pressure = systolic-diastolic

Question 13

Resistance: Equation (MAP = ___), causes of increase (3)

Answer 13

• MAP = CO x R
• Higher R = higher BP
• R increases with:
  
  • Smaller lumen (vasoconstriction)
  • Blood viscosity (mostly increased RBCs)
  • Length of vessel

Question 14

Venous Return: Causes

Answer 14

• Caused by pressure from left ventricle
• Decreased by increased pressure in right side of heart
• Also due to:
  
  • Skeletal muscle pump
  • Respiratory pump (abdominal cavity pressure goes up, thoracic cavity pressure goes down )

Question 15

Velocity of blood flow: Overview

Answer 15

• Inversely proportional to total cross-sectional area
• Branching causes cross-sectional area to increase
• BP can increase velocity

Question 16

BP Control - Neural: Regulator Reflexes for Baroreceptor and Chemoreceptor Reflexes

Answer 16

• Baroreceptor Reflex
  
  • Carotid sinus reflex - regulates brain BP
  • Aortic reflex - regulates systemic BP
  • More stretch = more impulses
  • Autonomic tone adjusted - CO and R adjusted
• Chemoreceptor Reflex
  
  • Carotid bodies and aortic bodies
  • Detect hypoxia, acidosis, and hypercapnia
    
    • Hypercapnia = CO2 retention; excess CO2
  • Vasoconstriction

Question 17

BP Control: Hormonal

Answer 17

• Renin-angiotensin-aldosterone (RAA) system:
  
  • Renin + angiotensin > angiotensin II
  • Angiotensin II vasoconstricts and stimulates aldosterone release (BP ^)
• Epinephrine/ NE - increase CO, increases blood flow to cardiac and skeletal muscle
• ADH - vasoconstriction and water retention
• Atrial natriuretic peptide (ANP) - released by atrial cells - promotes salt and water loss in urine

Question 18

Measuring Circulation: Pulse definition, tool used to measure pulse, pulse pressure equation, normal ratio (SBP, DBP, PP)

Answer 18

• Pulse - pressure wave through arteries
• Sphygmomenometer
  
  • Compresses brachial artery
  • Korotkoff sounds
    
    • 1st sound heard as blood begins to pass again = systolic BP
    • Sounds disappear = diastolic BP
  • Pulse pressure = SBP - DBP
  • Normal ratio = 3:2:1 (SBP,DBP, PP)

Question 19

Circulatory Pathways

Answer 19

• Systemic - aorta > body tissues > vena cavae
• Pulmonary - pulm. Arteries > lungs > pulm. veins
• Hepatic portal - venous blood from GI organs to liver

Question 20

Blood Pressure definition (Systolic BP and Diastolic BP)

Answer 20

• Hydrostatic pressure exerted by blood on vessel walls
  
  • Systolic BP = highest arterial pressure during systole
  • Diastolic BP = lowest arterial pressure during diastole
• Decreases with distance

Question 21

MAP equation

Answer 21

MAP = diastolic + 1/3 (pulse pressure)

• Pulse pressure = systolic - diastolic

Question 22

Pulse pressure equation

Answer 22

Pulse Pressure = systolic-diastolic

Question 23

Higher resistance = Higher ______

Answer 23

Higher BP

Question 24

What are the three causes of increased resistance?

Answer 24

• Smaller lumen (vasoconstriction)
• Blood viscosity (mostly increased RBCs)
• Length of vessel