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BRS (RF) > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

What is blood flow rate?

A

Volume of blood passing through a vessel per unit time. The overall aim for the CVS is the adequate blood flow through he capillaries to deliver respiratory substrate and remove excretory products

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2
Q

What is the equation for blood flow rate?

A

𝑸=∆𝒑/𝑹

Equation relates blood flow with pressure gradient /vascular resistance

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3
Q

What is vascular resistance?

A

Hindrance to blood flow due to friction between moving fluid and stationary vascular walls

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4
Q

What is a pressure gradient?

A

Pressure between two defined regions (A-B), increasing pressure gradient increases the flow rate

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5
Q

What are the three main factors that influences vascular resistance?

A

Blood viscosity
Vessel radius
Vessel length

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6
Q

What is the relationship between resistance and vascular radius?

A

Resistance is directly proportional to 𝟏/𝒓^𝟒

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7
Q

Which factor most influences vascular resistance?

A

Vessel radius
Blood viscosity and vessel length is fairly CONSTANT  resistance changes are thus attributed to vessel radius alterations.

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8
Q

What two main factors is blood flow determined by?

A

Pressure difference in the vascular bed

Vascular resistance

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9
Q

An increase in blood pressure ___ pressure difference?

A

Increases

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10
Q

How does arteriolar vasoconstriction influence vascular resistance?

A

Increases resistance

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11
Q

How does increased blood pressure influence blood flow?

A

Increases blood flow

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12
Q

How does arteriolar vasoconstriction influence blood flow?

A

Decreases blood flow

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13
Q

What is the approximate blood pressure referred to as?

A

Mean arterial blood pressure

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14
Q

Why can systolic and diastolic pressure be used to calculate mean arterial pressure?

A

There is minimal deviations through the arteriole supply

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15
Q

How does the vascular system facilitate effective nutrient exchange?

A

As blood traverses through the capillary bed, low velocity is required system enables blood to decelerate through vasoconstriction

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16
Q

What is the average value for venous blood pressure?

A

Negligible 0mmHg

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17
Q

What is the only factor that contributes to blood flow?

A

Resistance since the blood pressure gradient is equal to arteriole pressure

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18
Q

Why do arteriolar Smooth muscles display a state of partial constriction?

A

Describes as vascular tone. Partial contraction enables alterations to blood flow through constriction and dilation (room to accommodate movements)

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19
Q

What are the two main functions of independent radius adjustment of arterioles?

A

Match blood flow to the metabolic needs of specific tissues

Increase in metabolic activity within the muscle

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20
Q

How is blood flow matched to local tissues?

A

Match blood flow to the metabolic demands of specific tissues (regulated by intrinsic control - local endothelial-derived mediators), tissue determines blood requirement

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21
Q

What is the active hyperaemia?

A

Increase in organ blood flow, associated with increased metabolic activity of tissue

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22
Q

How does radius influence hyperaemia?

A

Increase in radius causes a decrease in vascular resistance, this increases blood flow resulting in active hyperaemia.

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23
Q

How is systemic arterial blood pressure regulated?

A

Regulated by extrinsic controls (nervous influence and hormonal control)

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24
Q

What is myogenic autoregulation ?

A

Reduction in blood temperature: Vasoconstriction arises (Relevant for peripheral vessels – the integumentary system). Decrease in radius, increases vascular resistance to subsequently decrease blood flow to superficial surface (Less heat radiation).
Baroreceptors detect stretch and blood pressure.

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25
Q

How does a reduction in blood temperature influence vascular radius?

A 
Vasoconstriction arises (relevant for peripheral vessels - the integumentary system)
Decreased radius increases vascular resistance to subsequently decrease blood flow to superficial surface (less heat radiation)
26
Q

Which receptors detect stretch and blood pressure?

A

Baroreceptors

27
Q

Which equation relates cardiac output with mean arterial pressure?

A

Cardiac output = Blood pressure (MAP) / Total peripheral resistance

28
Q

What is MAP equation in terms of cardiac output?

A

MAP = Q X TPR

29
Q

What is total peripheral resistance?

A

Sum of resistance of all arterioles present in systemic circulation

30
Q

What is mean arteriole pressure?

A

Average pressure within the venue system is negligible thus the pressure difference is equated to MAP

31
Q

How is arteriole blood pressure affected and altered?

A

Alterations to arteriole radii, influenced by neural and hormonal pathways

32
Q

Which centre controls the neural regulation of arterial blood pressure?

A

Regulated by the cardiac control centre within the medulla oblongata

33
Q

Which types of receptors facilitate constriction and dilation of arterioles?

A

Adrenoreceptors

34
Q

Which adrenoreceptor leads to constriction?

A

Alpha receptors

35
Q

Which adrenoreceptor leads to dilation?

A

Beta receptos

36
Q

Where is the cardiac control centre located?

A

Medulla oblongata

37
Q

What is the effect of vasoconstriction of blood flow?

A

Vasoconstriction decreased the radius, thus increasing resistance and decreases cardiac flow. Reduction preserves blood pressure to reduce cardiac output.

38
Q

Blood is preserved for which organ?

A

Brain

39
Q

What is the purpose of capillary exchange?

A

The delivery of metabolic substrates to respiring cells.

40
Q

What is the primary advantage for a thin endothelial cell?

A

Reduced diffusion distance assisting with effective diffusion of substances

41
Q

Describe the distribution of capillaries in terms of respiring cells?

A

Optimum accessibility to the capillaries, ensures that cells are proximal to vasculature

42
Q

What is the distribution of capillary density?

A

Variable within tissues beds

43
Q

What is Fick’s law?

A

Minimise diffusion distance, maximise surface area and maximise diffusion time

44
Q

How does capillary density relate to metabolic activity?

A

Increases capillary density to supply available respiring cells

45
Q

Which structures/regions have a high capillary density?

A

Skeletal muscle
Myocardium
Lungs

46
Q

Why does a brain require a high capillary density?

A

The brain is vulnerable to hypoxia

47
Q

Which tissue is poorly perfused?

A

Adipose tissue

48
Q

Which capillary sphincter is closed to regulate and divert blood flow to different tissues?

A

Precapillary sphincter

49
Q

What are the three types of capillaries?

A

Continuous
Fenestrated
Discontinuous

50
Q

What type of gap junctions are present within continuous capillaries?

A

Water filled gap junctions

51
Q

What can diffuse through continuous capillaries?

A

Electrolytes

52
Q

What are continuous capillaries?

A

Majority of capillaries have continuous structure. Water-filled gap junctions between endothelial cells, enabling passage of electrolytes. The endothelial wall is one cell thick; transporter proteins embedded within the capillary to export substrate to tissue.
Carrier proteins facilitate diffusion of metabolic substrates.

53
Q

What are fenestrated capillaries?

A

Fenestrations are pores within the capillaries, enables relatively larger molecules to pass through the capillaries into the tissue space (Larger gap junctions).

54
Q

What are discontinuous capillaries?

A

Relatively large holes in the capillary, important in bone marrow, leucocytes required to enter into systemic circulation post-haemopoiesis for maturation and activation.

55
Q

Which gap junctions are present within the brain?

A

Tight gap junctions

There are no water filled gap junctions

56
Q

What effect does hydrostatic pressure have on plasma?

A

Concept that specific amount of protein free plasma filters out of the capillary and mixes with surrounding interstitial fluid, hydrostatic force, forces plasma across the capillaries through the gap junctions or fenestrations; oncotic pressure, due to reduction in water potential and plasma protein.

57
Q

What is oncotic pressure?

A

Starlings forces; is the osmotic force due to protein in the capillary drawing water back in. Oncotic pressure is constant/uniform because the protein plasma concentrations do not change.

58
Q

Which part of the capillary bed has the highest pressure?

A

Arteriolar end

59
Q

What is the pressure relationship between hydrostatic and oncotic pressure at the arteriolar end?

A

Hydrostatic pressure > oncotic pressure = fluid leaves the capillary (ULTRAFILTRATION)

60
Q

What is the pressure relationship at the venular end?

A

Venular end: Oncotic pressure > hydrostatic pressure = fluid enters the capillary (REABSOPRTION)

61
Q

What is the net loss of fluid from capillaries?

A

1mm drains into lymphatic system

BRS (RF) (38 decks)

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