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Physiology 1 > Blood flow control > Flashcards

Blood flow control Flashcards

1
Q

What is total peripheral resistance (TPR)? [1 mark]

A

The total resistance to flow of blood in the systemic circuit.

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2
Q

What is the inverse of resistance? [1 mark]

A

Conductance (G) = 1/TPR

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3
Q

What is the formula for cardiac output? [3 marks]

A

Cardiac output (CO) = [Pressure gradient (Pa - CVP)]/Total peripheral resistance (TPR)

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4
Q

What does TPR control? [2 marks]

A
  • Blood flow

- Blood pressure

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5
Q

What factors control TPR? [3 marks]

A
  • Radius
  • Pressure difference across vessels
  • Length of vessel
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6
Q

What happens to the arterioles and to TPR and BP to cause a higher blood flow? [2 marks]

A
  • Arterioles dilate

- BP upstream and TPR decrease

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7
Q

What happens to the arterioles and to TPR and BP to cause a lower blood flow? [2 marks]

A
  • Arterioles constrict

- BP upstream and TPR increase

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8
Q

What happens to the arterioles in hypertension? [1 mark]

A

Over constriction

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9
Q

What happens to the superior mesenteric and common iliac post-prandial? [2 marks]

A
  • Superior mesenteric dilates

- Common iliac constricts

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10
Q

What happens to the superior mesenteric and common iliac during exercise? [2 marks]

A
  • Superior mesenteric constriction

- Common iliac dilates

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11
Q

What does the superior mesenteric arise from? [1 mark]

A

Anterior surface of the abdominal aorta

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12
Q

What does the common iliac arise from? [1 mark]

A

The abdominal aorta

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13
Q

What is Poiseuille’s law and what does it consider? [4 marks]

A
  • Describes the volume flow rate of a liquid through a tube
  • Viscosity decreases it
  • Vessel length decreases it
  • Radius increases it
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14
Q

What is the formula for resistance? [4 marks]

A

Resistance = (8 x viscosity [η] x length)/(π x radius^4)

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15
Q

What is the combined formula for Darcy’s and Poiseuille’s law?

A

CO = Pa - CVP x (πr^4)/(8ηL)

remember: conductance NOT resistance is in the equation

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16
Q

What is the pressure like in capillaries? [1 mark]

A

Low (because of less resistance)

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17
Q

What is the radius like in capillaries? [1 mark]

A

Constant (because of no innervation or smooth muscle)

18
Q

Why is there less resistance in capillaries? [1 mark]

A

Bolus flow (smooth flow)

19
Q

Why do vessels in parallel have less resistance? [1 mark]

A

If they were end to end, the total resistance would add up

20
Q

What are the two types of blood flow control? [2 marks]

A
  • Central (from brain)

- Local

21
Q

What are the two types of LOCAL blood flow control? [2 marks]

A
  • Intrinsic (within a tissue)

- Extrinsic (outside a tissue)

22
Q

What are examples of intrinsic blood flow control? [3 marks]

A
  • Tissue metabolites
  • Myogenic properties of muscle
  • Endothelial factors
23
Q

What are examples of intrinsic blood flow control? [2 marks]

A
  • Neural stimulation

- Hormones

24
Q

Why would having a linear relationship between blood flow and pressure be a bad thing? [1 mark]

A

There would be large differences in blood flow as pressure changes

25
Q

What happens in the Bayliss myogenic response? [2 marks]

A
  • At low pressures, vessels open a lot

- At higher pressures, it closes more (so there’s less fluctuation in blood flow)

26
Q

What does blood flow depend on? [3 marks]

A
  • Viscosity of blood
  • Vessel diameter
  • Haematocrit
27
Q

What is viscosity? [1 mark]

A

A measure of internal friction opposing the separation of the lamina (circles in flow).

28
Q

What are the clinical implications for haematocrit? [2 marks]

A

HIGH: Polycythaemia
LOW: Anaemia

29
Q

What are the clinical implications for RBC deformability? [3 marks]

A
  • High haematocrit
  • Low blood flow
  • Sickle cell anaemia
30
Q

What are the clinical implications for velocity? [2 marks]

A
  • Immobility (causes slow venous flow)

- Partial clotting (increases velocity)

31
Q

What happens to cardiac output when you breathe in? [3 marks]

A
  • Increases a little bit
  • Diaphragm moves down
  • Increases pressure
32
Q

What happens to veins at low pressures? [1 mark]

A

They collapse

33
Q

What happens to veins at high pressures? [1 mark]

A

They distend

34
Q

What helps venous return? [2 marks]

A
  • Thoracic pump

- Skeletal muscle contraction

35
Q

What does sympathetic venoconstriction increase? [3 marks]

A
  • Venous retun
  • Central venous pressure (increases preload and SV)
  • End-diastolic pressure
36
Q

What is central venous pressure? [1 mark]

A

The pressure of blood in the right atrium

37
Q

What is Bernoulli’s law? [1 mark]

A

Mechanical energy of flow is determined by pressure, kinetic and potential energies (ρ = fluid mass).

38
Q

What is the formula for Bernoulli’s law? [3 marks]

A

Energy = Pressure (PV) + kinetic ((ρV^2)/2) + potential (pgh)

39
Q

When standing, where is there more pressure? [1 mark]

A

In the heart

40
Q

When standing, where is there more kinetic energy? [1 mark]

A

Heart

41
Q

When standing, where is there more potential energy? [1 mark]

A

Heart

Physiology 1 (13 decks)

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