Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CVS > CVS 5 - Microcirculation > Flashcards

CVS 5 - Microcirculation Flashcards

1
Q

Describe the arrangement of microcirculation.

A
  1. 1st order arterioles
  2. Terminal arterioles
  3. Capillary
  4. Pericytic venule
  5. Venule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is blood flow rate?

A

Volume of blood passing through a vessel per unit time.

F = P/R (pressure gradient / vascular resistance)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is resistance?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the factors affecting resistance?

A
  1. Blood viscosity
  2. Vessel radius
  3. Vessel length

(blood viscosity and vessel length are generally constant)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is resistance directly proportional to?

A

1 / r^4

If radius decreases, Resistance increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which are the major resistance vessels?

A

Arterioles - where changes in BP occur

Blood pressure generated by the heart doesn’t change much in arteries

PRESSURE DIFFERENCE IS WHAT ALLOWS BLOOD TO REACH TISSUES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is normal blood pressure called?

A

Mean Arterial Pressure (MAP). In arteries, BP is around MAP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why do you want blood to go slowly through the capillary bed?

A

To allow nutrient exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Derive an equation knowing that initial pressure (A) is MAP and the final pressure (venous BP) is usually 0.

A

F (organ) = MAP / R (organ)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the major determinant of blood flow in the body?

A

The resistance of arterioles in the organ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is vascular tone?

A

Arteriolar smooth muscle is usually partially constricted.

They have to be partially constricted to regulate blood flow by dilating or constricting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the 2 functions that require arteriolar radii adjustment?

A
  1. Matching blood flow to metabolic needs of tissue - LOCAL INTRINSIC CONTROL (independent of nerves and hormones)
  2. Aids in regulating artery BP - EXTRINSIC CONTROL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is active hyperemia?

A

Increase in organ blood flow that is associated with increased metabolic activity of organ or tissue.

Arterioles respond to changes in chemical environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How can arterioles respond to changes in the physical environment?

A

e.g. temperature

If blood temp decreases, microcirculation will make arteriolar smooth muscle contract. Less blood reaches surface. Less heat radiated away.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe autoregulation.

A

In the physical environment, not all tissues need more blood (CO is limited, so body must be selective).

Therefore, certain tissues (e.g. lungs, heart, muscle) may undergo Active Hyperemia and dilate. Other (less metabolically active) tissues won’t.

e.g. if BP increases, less metabolically active tissues will sense the vasodilation (and the STRETCH) and they will consequently undergo myogenic vasoconstriction, so more blood doesn’t go across the tissue where it is not needed.

Whole process is called auto regulation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Give an equation that applies to the WHOLE of circulation.

A

CO = MAP/TPR (total peripheral resistance)

TPR = sum of resistance of all arterioles in the body

17
Q

Which 2 pathways can influence arteriolar radii?

A

Neural and hormonal

18
Q

Describe neural regulation of arterial BP

A
  1. Regulated by cardiovascular control system in medulla
  2. Vasonconstriction occurs to increase BP.

2 important receptors.

Beta receptor = on the heart. Important in speeding the heart up

Alpha receptor (important in microcirculation) = receptors that respond to noradrenaline and cause vasoconstriction.

19
Q

Describe hormonal regulation of arterial BP.

A

There are potent vasoconstrictor hormones.

Vasopressin (Posterior pituitary)
Angiotensin (mainly lung)
Adrenaline/noradrenaline

20
Q

What is the ultimate function of the CVS?

A

Capillary exchange - delivery of metabolic substrates to cells of organism

21
Q

2 ways in which capillaries are perfectly designed for exchange.

A
  1. Very narrow walls - 1um thick

2. Extensive branching - no capillary more than a few um from a tissue cell

22
Q

Why is capillary density important?

A

More metabolically active tissue means greater capillary density

23
Q

Why do the myocardium and brain need a high capillary density?

A

They are particularly vulnerable to hypoxia.

24
Q

Give an example of a poorly perfused tissue.

A

Adipose tissue

25
Q

Give one caveat to the high capillary density of skeletal muscle.

A

Most of the capillaries are shut off at rest.

PRECAPILLARY SPHINCTER SHUTS OFF ARTERIOLES/CAPILLARIES

26
Q

What are the 3 types of capillary.

A
  1. Continous
  2. Fenestrated
  3. Discontinuous
27
Q

Describe continuous capillaries.

MOST CAPILLARIES ARE CONTINUOUS

A
  1. Contain small water filled gap junctions between endothelial cells
  2. The small water filled gap junctions allow electrolyte/small molecule passage
  3. Most substances move through endothelial cells, not the junctions
28
Q

Describe fenestrated capillaries.

A
  1. These are leakier - they have fenestrae (slightly bigger holes), allow larger substances to diffuse through the fenestrations
29
Q

Describe discontinuous capillaries.

A
  1. LARGE holes in capillary

2. Particularly important in bone marrow when white cells have to get into blood

30
Q

In the blood-brain barrier, you do not have water-filled gap junctions between endothelial cells. What do you have instead? Why?

A

Really tight gap junctions

Means access of substances to the brain is tightly regulated.

Anything that needs to get to the brain must diffuse across the endothelial cells, so brain is more protected.

*some areas of the brain have normal gap junction structure

31
Q

What is bulk flow?

A

Volume of protein-free plasma filters out of the capillary, mixes with surrounding Interstitial fluid, and is reabsorbed

32
Q

What are the Starling forces? (forces which affect fluid movement in and out of the capillary)

A
  1. Hydrostatic pressure
  2. Oncotic pressure

Oncotic pressure = osmotic force due to protein in the capillary drawing water back in.

33
Q

Describe blood as it moves through capillaries.

A
  1. Highest BP at arteriolar end - hydrostatic pressure > oncotic pressure so ultrafiltration occurs.
  2. BP drops at the venular end (as arterioles are the major resistance vessels). Oncotic pressure is the same throughout.
  3. Venular end, oncotic pressure > hydrostatic pressure.
  4. However, not all of the fluid is reabsorbed into the capillary (9mmHg leaves, 8 mmHg reabsorbed).
  5. This extra fluid is drained by lymphatic system.
34
Q

Describe key features of the lymphatic system.

A
  1. NOT A CLOSED LOOP (unlike circulatory system) - there are blind ended lymphatic capillaries
  2. Contains valves which prevents backflow
  3. Fluid movement driven by lymphatic pressure (e.g. lungs inflating, muscle pressure)
  4. Single layer of endothelial cells.
  5. Large water filled channels - one way.
35
Q

What does lymph drain into?

A
  1. Thoracic duct
  2. Right Lymphatic duct
  3. Right subclavian vein
  4. Left subclavian vein
36
Q

When does oedema occur?

How can it be caused?

A

Rate of production > rate of removal

May be caused by parasitic blockage of lymph nodes

May cause elephantiasis (filaria)

CVS (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions