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Patho 1 > 2 - Circulatory > Flashcards

2 - Circulatory Flashcards

1
Q

What percentage of blood is in the veins at any given moment?

A

64%

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2
Q

What is the average functional pressure in most vascular beds?

In glomerulus?

A

17 mmHg

60 mmHg

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3
Q

What is Ohm’s Law?

A

Calculation for flow through a vessel:

F = (Delta P)/R

F is blood flow

Delta P is the pressure difference between the two ends of the vessel

R is resistance

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4
Q

What is the overall blood flow of an adult person at rest?

A

5000 ml/min

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5
Q

What is laminar flow?

A

When blood flows through a long smooth vessel, it flow in streamlines, with each layer of the blood remaining the same distance from the vessel wall

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6
Q

Why is parabolic velocity in blood vessels important?

A

MUCH faster

fluid in the middle of the vessel can move rapidly becuase many layers of the slipping molecules exist between the middle of the vessel and the vessel wall

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7
Q

Is turbulence higher in large or small vessels?

A

Large, especially with:

pulsatile flow

sudden change in vessel diameter

high velocity of flow

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8
Q

What is the definition of blood pressure?

A

force exerted by the blood against any unit area of the vessel wall

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9
Q

____ mmHG equals _____ cmH20

A

1 mm

1.36 cm

Mercury has a specific gravity 13.6 times that of water

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10
Q

Why do large diameter vessels conduct blood faster than small?

A

Laminar flow

Poiseuille’s Law

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11
Q

The ______ blood vessels in circuit,

the _____ the total vascular resistence

A

more

lower

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12
Q

Which is more distensible: veins or arteries?

A

Veins!

About 8x more distensible.

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13
Q

What is vascular compliance?

A

Total quantity of blood that can be stored in a given portion of the circulation

The compliance of a vein is about 24x higher than a corresponding artery

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14
Q

What two major pressures affect pulse pressure?

A

Stroke Volume

Vessel compliance/distensibility

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15
Q

What are four examples of specific blood resevoirs?

A
  1. The spleen (100 ml)
  2. the sinuses of the liver (several hundred)
  3. Large abdominal veins
  4. Venous plexus beneath the skin
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16
Q

What is the rough total surface area of the peripheral circulation?

A

500 to 700 square meters

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17
Q

How far is a single cell from a capillary (usually)?

A

20-30 micrometers

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18
Q

What is the intercellular cleft?

A

Pore in the capillary membrane that allow movement across the membrane

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19
Q

Brain capillary endothelial cells have what kind of cell junctions?

A

Tight junctions

Only allow water, O2 and COd to pass in or out

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20
Q

Describe the capillary intercellular clefts of the liver

A

Wide open, allowing almost all disolved substances in the plasma to pass into the liver (including plasma proteins)

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21
Q

Describe the endothelial clefts in the glomerular capillaries of the kidney

A

numerous oval windows (fenestrae) allow tremendous amounts of small molecular and ionic substances (but not plasma proteins) to filter through

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22
Q

What is vasomotion?

A

intermittent contraction of the metarterioles and precapillary sphincters

causes intermittent flow instead of continuous flow in capillaries

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23
Q

What is the #1 regulator of vasomotion? How?

A

Oxygen concentration in the tissue

When VO2 is increased, the intermittent periods of blood flow occur more often, allowing increased DO2

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24
Q

What is the interstitium?

A

The space between cells

Contains interstitial fluid

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25
Q

What is a brush pile?

A

in the interstitium, the proteoglycans form a mat of extremely fine filaments called a brush pile

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26
Q

How does free fluid usually exist in the interstitium?

A

As rivulets of free fluid and small free fluid vessicles

It doesn’t flow easily through the interstitial gel

With edema, these rivulets expand tremendously

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27
Q

capillary pressure moves fluid ______

A

out of the capillary

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28
Q

Plasma colloid osmotic pressure moves fluid ____

A

into the capillary

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29
Q

Interstital fluid pressure moves fluid ______

A

into the capillary

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30
Q

interstitial fluid colloid osmotic pressure moves fluid______

A

Out of the capillary

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31
Q

What is the net filtration pressure?

A

Sum of the four forces, determines which way filtration will occur

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32
Q

Why is the interstitial fluid pressure slightly negative?

A

The lympatic system pumps extra fluid and protein/molecules/debris from the interstitial space into the blood circulation, and this creates a slight negative pressure in the interstitial space

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33
Q

All the lymph vessels from the lower body empty into the _____, which empties into the blood system at the ________

A

thoracic duct

L IJ

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34
Q

2/3 of all lymph is derived from the ______

A

liver and intestines

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35
Q

Total estimated lymph flow

A

120 ml/hr

2-3 L/day

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36
Q

How are tissues held together in the body?

A

connective tissue fibers, but also the negative interstital fluid pressure!!!!

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37
Q

What happens with interstitial tissues lose their negative pressure?

A

Edema

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38
Q

what is beriberi?

A

Thiamine (vit B12) deficiency

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39
Q

Reactive Hyperemia

A

mechanism for local blood flow

WHen the blood supply to a tissue is blocked, once it’s unblocked the blood flow increases 4-7x normal. Lasts for seconds or hours.

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40
Q

Active Hyperemia

A

When a tissue becomes highly active with increased VO2, rate of blood flow increases

Increases skeletal blood flow 20 fold during exercise

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41
Q

Myogenic Theory of acute autoregulation

A

when the smooth mm cells of the vascular walls are stretched, they contract, and vice versa

this means flow in the arterioles remains almost exactly the same regardless of fluctuations in MAP

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42
Q

Myogenic contraction is initiated by ________

A

stretch induced vascular depolarization

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43
Q

Describe Tubuloglomerular Feedback

A

in the distal tubule, macula densa sense an increase in the amount of blood filtering through the glomerulus and constrict afferent arterioles, reducing renal blood flow back to normal

44
Q

The level of excitability in the brain is highly dependent on concentrations of what?

A

CO2

H+

45
Q

The most important endothelium-dervied relaxing factor is _______

A

nitric oxide

46
Q

What does NO do in vascular smooth muscle?

A

activates a cascade that leads to vasodilation

47
Q

How does NO contribute to effective local blood flow control?

A

When microvascular flow increases, NO is released upstream and dilates the feeding vessel, so that pressure isn’t excessive

48
Q

Why does Angiotensin II trigger NO synthesis and release?

A

Protect against excessive vasoconstriction

49
Q

How does Sildenafil work?

A

prevents degradation of cGMP (the secondary messenger that NO triggers) and prolongs the actions of NO that cause vasodilation

50
Q

What is endothelin?

When is it released?

Why?

A

extremely potent vasoconstrictor

Released by the endothelium when it’s been damaged

Prevents extensive bleeding from the damage

51
Q

Hypertension damages endothelium, worsening vasoconstriction by triggering release of ______

A

endothelin

52
Q

what causes retrolental fibroplasia?

A

Hyperoxia in preemies causes blindness after they are removed from the hyperoxic environment becuase the relative hypoxia causes uncontrolled angiogenesis in the retina and overgrows to the point of causing blindness

53
Q

Name four angiogenic factors

A
  1. VEGF
  2. Fibroblast growth factor
  3. PDGF
  4. Angiogenin
54
Q

What is the role of HIF in angiogenesis?

A

Reduced tissue oxygen induces expression of HIF (hypoxia inducible factors) which upregulate angiogenic factors

55
Q

Is vascularity determined by maximum or average blood flow need?

A

Maximum

(you’re not always exercising, but when you exercise consistently your body remembers the blood flow you needed during peak performance and creates enough vascularity to meet that maximum demand

56
Q

Laplace’s Equation for vessels

A

T = r x P

where t is vascular wall tension

radius is the radius of the vessel

and P is its pressure

57
Q

How do small blood vessels respond to prolonged hypertension?

A

constrict

inward eutrophic remodeling

smooth mm cells arrange themselves around the smaller diameter, basically bunching up to hold the smaller size permanently

58
Q

How do larger arteries respond to chronic hypertension?

A

Cannot constrict

vessel wall is exposed to increased wall tension

undergo hypertrophic remodeling

vascular smooth mm cells get bigger and develop collagen/fibrin to make the vessel wall stronger

MAKES BLOOD VESSELS STIFFER

59
Q

If veins have thin walls, why can you use a saphenous vein to replace an artery in a CABG?

A

Once it’s anastamosed, the increased pressure leads to hypertrophy of vascular smooth muscle cells

gets thicker and stronger, and after several months will be about as thick as an artery

60
Q

what does humoral control of the circulation entail?

A

substances secreted or absorbed into the body fluids affect blood pressure

61
Q

What are the humoral vasoconstrictors?

A

Norepinephrine/Epinephrine

Angiotensin II

Vasopressin

62
Q

Which is a more powerful vasoconstrictor: NE or Epi?

A

Norepinephrine

63
Q

During sympathetic stimulation, NE and epi function as both neurotransmitters and ______

A

hormones

adrenal medullae secretes NE and epi into the blood, causing direct vasoconstriction

64
Q

Angiotensin II constricts the ______

A

arterioles

65
Q

Where is vasopressin produced?

Where is it secreted?

A

Hypothalamus

Posterior Pituitary

66
Q

What are the humoral vasodilators?

A

Bradykinin

Histamine

67
Q

What are kinins?

A

substances that cause powerful vasodilation

68
Q

Bradykinin causes ______ and _______

A

Arteriolar dilation

increased capillary permeability

69
Q

Most histamine is derived from _____ in damaged tissues and ______ in the blood.

A

mast cells

basophils

70
Q

Histamines cause _____ and _____

A

arteriolar vasodilation

increased capillary permeability (edema)

71
Q

Increases in which ions cause vasodilation?

A

Increased potassium

Increased Magnesium

Increased Hydrogen

Increased acetate and citrate

Increased CO2

72
Q

Increased calcium causes vasodilation or vasoconstriction?

A

constriction

73
Q

An increase in CO2 will cause ________ in the brain

A

marked vasodilation in the brain, but stimulates brain vasomotor center which leads to widespread vasoconstriction in the body

74
Q

Sympathetic vasomotor nerve fibers leave the spinal cord through spinal nerves at:

A

T1-L2

75
Q

Once sympathetic nerves leave the vertebral column, they pass immediately in _______

A

a sympathetic chain

one on each side of the vertebral column

76
Q

In most tissues, all the vessels except ______ are innervated

A

capillaries

Precapillary sphincters and metarterioles are innervated

77
Q

Sympathetic vasoconstriction is most potent in what tissues?

A

kidneys

intestines

splen

skin

78
Q

Sympathetic vasoconstriction is less potent in what tissues?

A

skeletal muscle

heart

brain

79
Q

Where is the vasomotor center?

A

bilateral

medulla and lower third pons

80
Q

The vasomotor center transmits parasympathetic impulses through the _______ to the _______, sympathetic impulses through the ______ and _____ to ________

A

vagus nerves to the heart

spinal cord and peripheral sympathetic nerves to virtually all arteries, arterioles, and veins of the body

81
Q

Which portion of the vasomotor center transmits excitatory impules to the heart?

A

Lateral

82
Q

Which portion of the vasomotor center decreases heart rate and contractility?

How?

A

Medial

sends signals to the adjacent dorsal motor nuclei of the vagus nerves

83
Q

What is the reticular substance/formation?

A

complex network of brain and brainstem nuclei that can excite or inhibit the vasomotor center

84
Q

________ is the sympathetic vasoconstrictor.

A

Norepinephrine

85
Q

Norepinephrine acts directly on _______ receptors in vascular smooth muscle.

A

A adrenergic

86
Q

When sympathetic impulses are sent to the blood vessels, they are also sent to the ________

A

adrenal medullae

87
Q

Sympathetic stimulation of the adrenal medullae causes what?

A

medullae secret epinephrine and norepinephrine into the circulating blood

88
Q

When rapid control of arterial pressure is needed, what three things happen in the autonomic nervous system?

A
  1. Arterioles are constricted, increasing SVR
  2. The veins especially are strongly constricted
  3. the heart is directly stimulate by the autonomic nervous system, enhacing pumping
89
Q

Your nervous system can double or halve your BP in as little as ________

A

10 seconds

90
Q

Baroreceptors are extremely abundant in which two areas?

A

wall of each internal carotid artery (carotid sinus)

the wall of the aortic arch

91
Q

Signal from carotid baroreceptors travel to the brain via _______.

Signals from the aortic baroreceptors travel to the brain via _______.

Both pathways lead to the ________

A

Herings nerves to glossopharyngeal nerve

vagus nerves

nucleus tractus solitarius of the medulla

92
Q

Baroreceptors respond much more rapidly to a pressure that is ______ than a pressure that is ________

A

rising

stationary

93
Q

What happens when high pressure baroreceptor signals enter the nucleus tractus solitarius of the medulla?

A

secondary signals inhibit the vasoconstrictor center and excite the vagal parasympathetic center

94
Q

How long does it take for baroreceptors to reset when BP is chronicly increased/decreased?

A

1-2 days

This is due to resetting of the sensors themselves, not the vasomotor center

95
Q

Where are the chemoreceptor organs?

A

2 carotid bodies in the common carotid artery

1-3 aortic bodies adjacent to the aorta

96
Q

What nerves do chemoreceptor excite?

A

Same as baroreceptors:

Hering’s in the carotid

Vagus in the aorta

97
Q

At what blood pressure are chemoreceptors generally excited?

A

80mmHG

has to be really low before they’ll take action, so not a strong arterial pressure controller unless profound hypotension is present

98
Q

What effect does atrial stretch have on renal sympathetic activity?

ADH?

ANP?

A

Decreases renal

Decreases ADH

Increases ANP

99
Q

What are low-pressure receptors?

Why are they important?

A

Stretch receptors in the atria and pulmonary arteries

Helpful in adjusting BP when large changes in volume are present

100
Q

What is the bainbridge reflex?

A

Atrial stretch increases heart rate

101
Q

What is the CNS ischemic response?

A

When decreased blood flow (and therefore elevated CO2) in the vasomotor center are severe, the vasomotor center excites the vasoconstrictor and cardioaccelerator neurons.

SBP and HR skyrocket

102
Q

CNS ischemic response only occurs at severely low BP, so it’s often referred to as _______

A

Last-ditch stand presure control mechanism

103
Q

What is the Cushing Reaction?

A

Special type of CNS ischemic response

triggered by increased CSF pressure

When CSF pressure is higher than SBP, this stimulates and increase in SBP so that the brain can be perfused

104
Q

What is the abdominal compression reflex?

A

When baroreceptors or chemoreceptors are activated, skeletal nerves to the abdomen are stimulated and compress the abdomen

Increases venous return

105
Q

Why is it that people who have been paralyzed are considerably more prone to hypotensive episodes?

A

Unable to mount abdominal compression reflex

106
Q

How does skeletal muscle increase CO and BP during exercise?

A

Increases venous return

Patho 1 (17 decks)

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