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Physiology > Cardiology II > Flashcards

Cardiology II Flashcards

1
Q

Circuits in Series

A
  • Flow must be equal

- CO of R & L heart are inter-dependent bc of their series arrangement

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2
Q

Hemodynamics

A
  • Blood flows in a CLOSED system
  • Blood is non-compressible
  • Blood is heterogenous
  • Vessels are compliant, not rigid
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3
Q

Large artery

A
  • Thick walled

- Under high pressure

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4
Q

Large vein

A
  • Thin walled

- Under low pressure

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5
Q

Area & volume in blood vessels

A
  • Capillaries have biggest cross sectional area

- Veins contain greatest amount of blood

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6
Q

Flow equation

A

Q = ∆P/R

  • Q = flow
  • P = pressure
  • R = resistance
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7
Q

Flow (Q)

A

How much travels

- volume flow per unit time

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8
Q

Velocity (v)

A

How fast it travels

  • rate of displacement of blood per unit time
  • Inversely proportional to TOTAL cross- sectional area
  • Fastest in aorta & slowest in capillaries
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9
Q

Velocity equation

A

v = Q/A

- A = total cross sectional area of tube through which blood flows

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10
Q

Flow vs velocity

A
  • If flow through a tube is constant, then velocity increases as total x-sectional area decreases
  • As vessel diameter increases, velocity of flow through the vessel decreases.
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11
Q

Smallest vessel

A

aorta

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12
Q

Medium vessel

A

all of the arteries

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13
Q

Largest vessel

A

all of the capillaries

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14
Q

Why is velocity the slowest in the capillaries?

A

Total cross-sectional area of ALL capillaries combined is huge!

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15
Q

Laminar flow

A
  • Streamline
  • Concentric lamina slide past 1 another
  • Viscous forces dominate
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16
Q

Turbulent flow

A
  • Eddy currents
  • Noisy
  • Larger pressure required to maintain constant flow through turbulent areas
  • Inertial forces dominate
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17
Q

When is flow turbulent?

A

If Reynold’s # is > 3000

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18
Q

Reynold’s equation

A

Re = vpD/n

  • v = velocity
  • p = fluid density
  • D = tube diameter
  • n = viscosity
  • If Re is greater than 2000, there is an increasing likelihood that blood flow will become turbulent
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19
Q

When is flow laminar?

A

If Reynold’s # is < 2000

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20
Q

Anemia

A
  • Associated w/ decreased hematocrit, mass of RBCs, & viscosity
  • Decreased viscosity –> increase in Re
21
Q

What does anemia cause?

A

Turbulent flow & functional murmurs

22
Q

Thrombi

A

Blood clots in the lumen of vessels

- Diameter narrows, increasing blood velocity at the site of thrombus

23
Q

Flow vs pressure

A

Flow is dependent upon pressure difference

24
Q

Pressure gradient equation

A

∆P = (P1 - P2)

- Direction: high to low pressure

25
Q

Flow vs resistance

A

Increasing resistance –> decreased flow

26
Q

Resistance equation

A

R = ∆P/Q

27
Q

What is the major mechanism for changing resistance in the CV system?

A

Changing resistance of blood vessels (mainly arterioles)

28
Q

Resistance to blood flow

A
  • R is directly proportional to viscosity
  • R is directly proportional to length
  • R is inversely proportional to the 4th power of the radius ** MOST IMPORTANT!
29
Q

Resistance (Poiseuille) equation

A

R = nl8/r4π

30
Q

Series (vascular beds)

A

Blood flows from 1 vessel to another in sequence

31
Q

Parallel (vascular beds)

A

Blood flow is distributed simultaneously among parallel vessels

32
Q

Series resistance

A
  • Sequential arrangement

- Total resistance = sum of individual resistances

33
Q

Effects of sequential arrangement

A
  • Total flow through each level of the system is the same

- Pressure decreases progressively

34
Q

Parallel resistance

A
  • Simultaneous arrangement

- Total resistance is less than any individual resistances

35
Q

Effects of simultaneous arrangement

A
  • Mean pressure in each artery will be close to mean pressure in the aorta
  • Adding a new resistance to the circuit decreases total resistance
36
Q

Control of BP

A
  • Baroreceptor reflex: Neurally-mediated, reacts in seconds

- Renin-angiotension-aldosterone system: Hormonally mediated, reacts in minutes to hours

37
Q

Baroreceptors

A
  • Mechanoreceptors located in carotid sinus & aortic arch
  • Sensory afferents carry pressure info to CV centers in brainstem
  • CV centers coordinate a ∆ in output of ANS
  • Efferent neurons direct ∆s in heart & blood vessels
  • Strongest stimulus = rapid ∆ in pressure
38
Q

Baroflex via ANS

A
  • Decrease PNS to heart –> HR increases

- Increase SNS to blood vessels –> BP increases

39
Q

Systolic pressure

A
  • Highest arterial pressure during cardiac cycle

- Pressure in artery after blood has been ejected from LV during systole

40
Q

Diastolic pressure

A
  • Lowest arterial pressure during cardiac cycle
  • Pressure in artery when no blood is being ejected from LV
  • DBP decreases when TPR decreases
41
Q

What happens at the initiation of exercise?

A

Muscle mechanoreceptors & chemoreceptors trigger reflexes that send afferents to the motor cortex

42
Q

Motor cortex

A

Directs responses to increase sympathetic outflow to the heart & blood vessels

  • Heart = increase HR & contractility
  • Blood vessels = arteriolar constriction & venoconstriction
  • Venoconstriction increases VR to heart
43
Q

Why is increase in VR essential?

A

Provides increased EDV (needed to produce increase in SV & CO)
- Frank-starling mechanism

44
Q

Local responses in skeletal & cardiac muscle

A
  • Metabolites build up (lactate, K+, nitric oxide, adenosine)
    ˚ Leads to vasodilation of arterioles
    ˚ Increases local blood flow to muscles
  • Prominent response –> Decrease in TPR
  • Dominate in heart
    ˚ Vasodilation mediated by adenosine & decreased PO2
    ˚ Leads to increased coronary blood flow
45
Q

Pulse pressure increase in exercise

A
  • Large amount of elastic tissue in arteries –> stiff & noncompliant
  • During systole, blood is rapidly ejected into aorta/arteries –> arterial pressure increases from lowest (diastole) to highest (systole)
  • Magnitude of increase = pulse pressure
  • PP depends on SV & compliance of arteries
  • PP increases in exercise bc SV increases
46
Q

Cutaneous blood flow

A
  • Exhibits a biphasic response to exercise
  • Early – vasoconstriction of cutaneous arterioles occurs as a result of the sympathetic alpha1 receptor activity
  • As exercise progresses, body temp increases secondary to O2 consumption
47
Q

VO2 max

A

Point at which O2 consumption fails to rise despite increased exercise intensity or power output
- O2 consumption shows a plateau

48
Q

O2 exchange in lungs

A
  • Restores PO2 to its normal arterial value of 100mmHg
  • In exercise, while venous PO2 is lower than normal, rapid diffusion of O2 from alveolar gas raises PO2 in arterial blood back to normal
  • Only compromised in people w/ lung disease

Physiology (7 decks)

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