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Physiology I > Exam 2 Part II - All circulation related topics > Flashcards

Exam 2 Part II - All circulation related topics Flashcards

1
Q

Tissue flow is primarily determined by what?

A

“local factors” (that modify

local r4 resistance)

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2
Q

What is the total blood volume?

A

5 liters (5000mL)

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3
Q

What two areas combined receive 50% of the cardiac output (2.5 liters) at rest?

A

Kidneys and GI tract (with liver)

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4
Q

What circulation system is of supreme importance in a healthy systemic circulatory system?

A

Coronary circulation

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5
Q

What happens to flow in the left coronary artery during ventricular systole?

A

Flow decreases

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6
Q

What happens to flow in the left coronary artery during ventricular diastole?

A

Flow increases

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7
Q

What are the two mechanisms involved in control of flow in the coronary circulation and which one is the main mechanism?

A
  • sympathetic fibers cause vasodilation

- local metabolic factors from cardiac myocytes cause vasodilation - this is the main one

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8
Q

How do sympathetic fibers on coronary arteries cause vasodilation?

A

By way of β2 receptors on vascular smooth muscle

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9
Q

How do local metabolic factors from cardiac myocytes cause vasodilation?

A

by the release of CO2 and H+, and particularly adenosine in the heart

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10
Q

Obstruction of any coronary artery can cause intense pain due to what?

A

Myocardial ischemia (inadequate blood supply)

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11
Q

If myocardial ischemia progresses, it can lead to what?

A

Myocardial infarction (AKA heart attack) which is death of cardiac muscle tissue

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12
Q

Total flow to the skeletal muscle is extremely variable depending on exercise/activity. At rest, what is the typical flow per average volume of tissue? What can it rise to during strenuous exercise?

A
  • average flow = 4 ml/min/100g of tissue at rest
  • can rise to 80 ml/min/100g of tissue during strenuous exercise of muscle (a 20 fold difference due to active hyperemia!)
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13
Q

What happens to blood flow to skeletal muscle during contraction?

A

Blood flow decreases during contraction (due to compression of vessels)

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14
Q

What happens to blood flow to skeletal muscle during relaxation?

A

Blood flow increases

Due to release of compression on vessels

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15
Q

There are two mechanisms that control blood flow to skeletal muscle. What are they and which one is primary?

A
  • sympathetic fibers
    cause vasoconstriction OR vasodilation
  • local metabolic factors from skeletal myocytes cause vasodilation - this is the main mechanism
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16
Q

How does nervous innervation of skeletal muscle arteries by sympathetic fibers
causes vasoconstriction OR vasodilation !?!?

A
  • some areas have α1 receptors and produce vasoconstriction
  • some areas have β2 adrenergic receptors for cholinergic
    sympathetic innervation, producing vasodilation
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17
Q

How do local metabolic factors from skeletal myocytes cause vasodilation?

A

by the release of CO2 and H+, and others (such as adenosine and K+)

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18
Q

What is the system wide phenomenon of mass sympathetic discharge and how does it affect flow?

A

↑ cardiac output and wide-spread vasoconstriction causes higher centers or cortical, motor areas to accentuate sympathetic activity which = ↑ heart rate, ↑ arterial BP (and venous pumping for venous return), better delivery of blood

i. e. just THINKING about exercise can ↑ heart rate (thus, can be
anticipatory) !

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19
Q

Which circulatory system is the most crucial for survival and therefore given the highest priority?

A

Cerebral circulation because it is the least tolerant area of ischemia

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20
Q

There is one mechanism that controls flow in the cerebral circulation. What is it?

A

local metabolic factors from neurons cause vasodilation

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21
Q

How do local metabolic factors from neurons in the cerebral circulation cause vasodilation?

A

by the release of CO2 and H+

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22
Q

What is the average volume of CSF?

A

~ 150 ml

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23
Q

What is the average daily turnover of CSF?

A

~500 ml/day

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24
Q

How does CSF chemical composition differ from regular plasma?

A

↑ Na+
↓↓ glucose
↓↓↓ K+

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25
Q

What is included in the splanchnic circulation?

A

G.I. Tract, liver, spleen

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26
Q

What circulation system is given the lowest priority in terms of distribution of cardiac output?

A

Splanchnic circulation

would you rather run away from disaster or stay and digest a meal?

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27
Q

There are tow mechanisms involved in control of flow in the splanchnic circulation. What are they and which one is primary?

A
  • local metabolic factors from G.I. tissues (including various glands)
    cause vasodilation
  • nervous innervation is the primary control mechanism and easily override local metabolic factors.
    *sympathetic stimulation = vasoconstriction
    *parasympathetic stimulation = vasodilation
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28
Q

How do local metabolic factors from G.I. tissues (including various glands)
cause vasodilation?

A

by the release of CO2 and H+, adenosine, and others

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29
Q

How does nervous innervation of the G.I. tract arteries by sympathetic fibers
cause vasoconstriction?

A

By α1 receptors which causes vasoconstriction which is an essential addition during situations where blood would be more appropriately directed to other, more important, areas

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30
Q

How does nervous innervation of the G.I. tract by parasympathetic fibers cause vasodilation?

A

parasympathetic stimulation (especially to stomach and large intestine) promotes glandular activity which causes vasodilation

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31
Q

A manifestation of ischemia to the gut due to competing body of blood flow that does not prioritize the gut is called what?

A

Abdominal cramps

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32
Q

The liver receives blood from two different sources? What are they and what percentage of blood flow to they contribute?

A

~75% of blood from the hepatic portal vein

~25% of blood from the hepatic artery

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33
Q

The spleen can store up to _______ (volume) of concentrated RBCs

A

~ 50ml

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34
Q

The kidneys receive a huge percentage of cardiac output. What percentage is this?

A

~ 22% of cardiac output

35
Q

The blood flow tot eh kidneys is rather steady, but can vary. What causes it to vary?

A

Exercise - it varies to maintain filtration of blood with increased metabolic activity

36
Q

The circulation system that is significantly large area that can call for large amounts of blood, and
given priority for temperature regulation?

A

Skin circulation

37
Q

The flow rate to the skin is extremely variable. What is the range of % of cardiac output that is received by the skin?

A

from 0 to 30% of cardiac output!!!

38
Q

What is meant by stating that the skin circulation is a controlled heat radiator?

A

It is a regulator of core body temperature by bringing blood close to the surface of the body to allow for heat loss by radiation and convection (and provide fluid for sweat glands to add evaporative cooling)

39
Q

When the special sub-region of the hypothalamus is exposed to an increased core temperature, what happens to the vessels in the skin circulation?

A

vasodilation and sweating

40
Q

When the special sub-region of the hypothalamus is exposed to an decreased core temperature, what happens to the vessels in the skin circulation?

A

vasoconstriction and no sweating

41
Q

Control of flow in the skin circulation is regulated by one mechanism. What is it?

A

nervous innervation of the skin arteries by sympathetic fibers
-stimulation causes
vasoconstriction (for cold environments)
- inhibition of sympathetics causes vasodilation (for hot environments)

42
Q

How does nervous innervation of the skin arteries by sympathetic fibers causes
vasoconstriction (for cold environments)?

A

α1 receptors on vascular smooth muscle cells that act like sphincters to
cause by-pass of blood through upper area aspects of the dermis (shunts)

one exception to all this… when cold penetrates deep into the dermis,
the vascular smooth muscle get too cold to maintain their normal metabolism resulting in vasodilation!!!

43
Q

Other than vascular smooth muscle cells creating shunts in response to sympathetic stimulation, how else does the body respond to cold to enhance the sympathetic response?

A

cold also triggers epinephrine release from adrenal gland - further enhancing the sympathetic effect

44
Q

Why are local factors not important in control of flow in the skin circulation?

A

because the integument gets ~10 times more flow than it would generally need for its metabolism due to its prioritization with cardiac output distribution

45
Q

What kind of innervation is responsible for causing sweating?

A

cholinergic sympathetic fibers innervate sweat glands and cause
sweating

46
Q

What kind of pump is the right ventricle?

A

Volume pump, meaning it must pump same volume as left ventricle per unit time (left ventricle was a “pressure pump”)

47
Q

What is the normal SBP of the RIGHT ventricle?

A

22 mmHg (compared to 120 mmHg fo rather LEFT ventricle)

48
Q

What is the normal DBP for the RIGHT ventricle?

A

8 mmHg (compared to 80 mmHg for the LEFT ventricle

49
Q

What is the RIGHT ventricular pulse pressure?

A

14 mmHg (very different from systemic arterial BP!)

50
Q

What is the mean pressure in the arteries of the pulmonary circulation?

A

~ 13 mmHg

51
Q

What is the mean pressure in the capillaries of the pulmonary circulation?

A

~7 mmHg

pulmonary capillary pressure is rather low (perhaps ½ of a typical systemic capillary)

52
Q

What is the mean pressure in the pulmonary vein of the pulmonary circulation?

A

~ 0mmHg

53
Q

There are 3 recognized zones of blood stratification in the lungs. What are they?

A
  • upper 1/3 - under-perfusion
  • middle 1/3 “just right” perfusion
  • lower 1/3 - over-perfusion
54
Q

What is the volume of blood in the pulmonary circuit?

A

~450 ml

55
Q

What volume (out of 450 ml total volume in pulmonary circuit) is found in the pulmonary capillaries?

A

~75 ml

56
Q

what controls blood flow to and through the pulmonary system?

A

local metabolites cause vasoconstriction

NOTE: recall how tissue flow in all other circulation systems is primarily determined by “local factors” that modify local r^4 resistance (vasodilation)… it’s opposite with the pulmonary circulation

57
Q

How does the release of local metabolites in the pulmonary system control blood flow through vasoconstriction?

A

Decreased oxygen levels will stimulate a protective mechanism which vasoconstricts vessels in the area of low oxygen to redirect blood to better oxygenated areas instead

58
Q

What ultimately sets pulmonary flow?

A

VENOUS RETURN to the right ventricle which is set by the collective metabolism of the body tissues

59
Q

What is the tissue in which capillaries travel called?

A

“interstitium” – in histology often termed the “ECM”

60
Q

Molecular/fluid movement in the capillary bed is a function of some basic factors:

A
  • solubility
  • size
  • capillary permeability
  • concentration
  • pressure
61
Q

There are three different types of capillaries that all have different levels of permeability. What are the three types of capillaries - list in order of permeability from least to most?

A
  • Type I (“continuous”) - permeable to small or lipid-soluble molecules
  • Type II (“fenestrated”) - allow for a great deal of fluid leakage and filter as a function of pressure dynamics
  • Type III (“sinusoidal”) - allow for wholesale leakage (even of entire cells)
62
Q

Other than capillary type (which is constant at any one location), what else drives permeation of at capillary bed (that can be modified)?

A

pressure dynamics between blood and interstitium

63
Q

What are the 4 major forces that contribute to pressure dynamics between blood and interstitium and determine net fluid exchange between them?

A
  • capillary pressure (AKA hydrostatic or blood pressure)
  • interstitial free fluid pressure
  • plasma colloidal osmotic pressure (AKA “oncotic” pressure)
  • interstitial fluid colloidal osmotic pressure
64
Q

When capillary pressure, interstitial free fluid pressure, plasma colloidal osmotic pressure and interstitial fluid colloidal osmotic pressure are taken collectively, they produce what?

A

Net driving force

65
Q

What plasma protein has the largest contribution to plasma colloidal osmotic pressure?

A

Albumin

66
Q

What is the formula for calculating net driving force?

A

NDF = [(Pc – Pt) – (πc– πt)]
Net driving force = (capillary pressure - interstitial free pressure) - ( plasma colloidal osmotic pressure - interstitial fluid colloidal osmotic pressure)

67
Q

The capillary pressure (Pc) is variable from arteriole to venous end. What is its range?

A

24 mmHg at arteriole end to 10 mmHg at venous end

68
Q

What is the net driving force at the arteriole end under normal conditions?

A

+7 mmHg

69
Q

What is the net driving force at the venous end under normal conditions?

A

-7 mmHg

70
Q

What happens to net filtration at the capillary bed when net driving force is greater than 0mmHg, as seen at the arteriole end of the capillary bed?

A

Net filtration OUT

71
Q

What happens to net filtration at the capillary bed when net driving force is less than 0mmHg, as seen at the venous end of the capillary bed?

A

Net filtration IN (AKA reabsorption)

72
Q

Of the four forces that determine net fluid exchange between blood and interstitium in the capillaries, which one is the only one that is variable?

A

Capillary pressure (Pc)

73
Q

Of the four forces that determine net fluid exchange between blood and interstitium in the capillaries, which one directs force inward (i.e. resists fluid loss at capillaries)?

A

Plasma colloidal osmotic pressure (πc)

74
Q

The net driving force varies across an entire systemic capillary but an equilibrium point is found at roughly the midpoint of the capillary. What is this point called?

A

Starling equilibrium

75
Q

There is a net fluid loss from the arteriole end to the equilibrium point and a net fluid reabsorption from the equilibrium point to the venule end. However, across the entire capillary system, is there a net fluid loss or reabsorption?

A

Net fluid loss of approximately 2-3 ml/min

76
Q

There is a slight net ______ filtration pressure in

the typical systemic capillary.

A

OUTWARD

NDF (net out) will be 0.3 mmHg which produces a systemic vascular filtered plasma loss of
approximately 2-3 ml/min

77
Q

What happens to the systemic vascular filtered plasma loss of
approximately 2-3 ml/min?

A

Most of the lost cardiovascular plasma filtrate that leaves capillaries are promptly conducted into the lymphatic system

78
Q

every time a skeletal muscle contracts, lymph fluid flows, known as the ________.

A

lymphatic pump

79
Q

What effect does increased interstitial free fluid pressure have on lymphatic fluid flow?

A

↑ interstitial free fluid pressure → ↑ lymphatic fluid flow

80
Q

In regards to capillary circulation, what is the “safety factor”

A

The range on either side of normal interstitial free fluid pressure ( ~ -6mmHg) where fluid will continue to be conducted into the lymphatic system.

81
Q

What happens when the “safety factor” is exceeded?

A

If this range (“safety factor”) is exceeded, fluid will pour into the tissues, creating an excessive increase in interstitial free fluid pressure and resulting in edema

82
Q

What is edema?

A

fluid (plasma filtrate) accumulation in tissues

83
Q

What are 4 possible causes of edema?

A
  • increased capillary permeability (due to damage)
  • increased capillary pressure (from altered BP/flow dynamics)
  • decreased colloidal osmotic pressure (due to decreased plasma protein from nephrosis, starvation of loss of albumin)
  • increased interstitial free fluid pressure (due to blockage of the drainage from the lymphatic system - often parasitic or surgically induced)

Physiology I (15 decks)

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