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Physiology Winter 2012 > Physiology 12.13.12 Circulation through Individual Tissue Beds > Flashcards

Physiology 12.13.12 Circulation through Individual Tissue Beds Flashcards

1
Q

Is sympathetic tone always present in coronary circulatino

A

yes

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2
Q

What changes the flow to heart

A

local metabolites produced by working msucle

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3
Q

Blood flow is proportional to what

A

Rate of work

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4
Q

Is flow slowed or increased during contraction of heart

A

slowed

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5
Q

What is ht mL/min of coronary blood flow at rest

A

250 mL/min

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6
Q

What % of coronary blood flow supplies left heart? right heart?

A

80% left heart

remainder ot right heart

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7
Q

What % of CO is coronary blood flow at rest

A

5%

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8
Q

Where do the major coronary arteries arise form?

A

Aorta distal to aortic valve

and provide virtually all the arterial blood supply

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8
Q

Describe the venous drainage of the myocardium

A

Coronary capillary blood flows via venules to veins that reach epicardial surface of heart and parallel teh arterial supply back to Coronary sinus

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9
Q

How do most of hte left ventricular capillary blood reach the right atrium

A

by wa of coronary sinus

small portion (of right ventricle capillaries) reaches right atirum by way ANTERIOR CARDIAC VEIN

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10
Q

What are thesbian veins

A

how inconsequential amt of blodo reaches cardiac ventricels direclty

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11
Q

What are factors that influence coronary blood flow

A

Aortic Pressure during Diastole

Extravascular Compression (squeezing of vessels during systole)

Sympathetic effects

Metabolic Factors

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12
Q

Coronary BF and Aortic P

A

Aortic P provides DF for BF through coronary arteries

During Diastole, flow is direclty proportional to aortic pressure

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13
Q

Severe hypothension (shock) and Coronary BF

A

Low aortic P may limit coronary BF

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14
Q

Increase in mean aortic P during exercise

A

increased ocronary BF

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15
Q

Extravascualr compression (squeezing) of myocardial vessels

A

occurs during cardiac systole

Compression reduces vascular diameter –> Increase vascular resistance –> decreases flow

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16
Q

What can happen during isovolumentric contraction of left ventricle

A

Extravascular compression is so great that flow in the left coronary artery may reverse momentarily

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17
Q

When is extravascular compression a problem

A

with sustained hypertension

Elevated afterload on LV increases ventriuclar work and O2 demand while also increasing extravascular compression

Combo increses the need for blood flow and restricts it as well

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18
Q

During conditions with reduced BF to heart (coronary occlusion or hypotension) is damage more likely to the inner (endocardial) wall of ventricle or outer (epicardial) wall

A

Inner Endocardial Wall

b/c extravascular compression is more significant

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19
Q

Does extravascular copression disturb coronary flow in right ventricle

A

not as much bc myocardial pressure is not nearly as reat

Total flow in right coronary artery is actually greater during systole than diastole b/c of greater driving pressure during systole

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20
Q

Sympathetic effect on coronary blood flow

A

Stimulation of sympathetic nerves to heart increases BF indirectly

In normal circumstances, sympathetic stimulation increases coronary BF by increasing HR and contractility whih increases Cardiac worka nd Myocardial O2 consumption

The resuling decerase in tissue O2 increases coronary BF by METABOLIC REGULATION

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21
Q

What happens if inotropic and chornotorpic effects of smpahteric stimulation are inhibited by beta adrenergi blocker

A

symp stimu decreases BF suggestion that alpha adrenergic vasoconstriction of cornoary vessels has occurred

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22
Q

What metabolites are implicated in metabolic mechainism which O2 demands triggers coronary vasodilation

A 
H+
lactic acid
Co2
Adenosine
Endothelial derived relaxing factor (NO)
K+

The more oxygen consumed, the more coronary blood flow

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23
Q

What happens during progressive ischemia (causing hypoxia) of myocardial tissue

A

stiualtes growth of colalteral vessels allowign more blood (O2) to reach ischemic area

Severe ischemia of cardiac tissue gives rise to chest pain (angina pectorsi)

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24
Q

What can releive angina

A

adminitstration of nitrites (nitroglycerin or ayl nitrite)

Gives rise to NO, acts as systemic vasodialtors, esp dilating coronary arterioles – .decreaseing afterload against whcih LV works

THis decreases myocardial O2 deman ,relieves myocardial ypoxia and angina

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25
Q

What is the O2 consumption in the non-exercising invididual

A

8-10 ml/min/100g of heart

Even at rest the herat is owrking

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26
Q

How much does O2 consumption increase during exercise

How does this affect coronary BF

A

It increases 5x during exercise

The increased delivery of O2 during exercise must be met by increasing coronary BF

27
Q

Work formula

A

Work = Pressure x Volume

Aortic Pressure is the P against

28
Q

What is the work of the heart when SV is 120 mL agasint MEP of 90 mm Hg, or a SV of 60 mL agasints MAP of 180 mmHG

A

Same!

29
Q

Does icreasing Aortic Pressure or SV demand more O2 ?

A

but Elevating aortic P increases O2 demand more than increasing SV

30
Q

How much O2 does Right heart require vs left heart. Why

A

Right heart only needs 1/5 O2 supply b/c PULMONARY ARTERY SYSTOLIC P is only 1/5 Aortic Systolic Pressure

Right heart only does 1/5 of the work since same CO

31
Q

What hpapens when heart adapts to increased afterload

A

Ventricular Dialtion! common adaptiation in cardiac failure

32
Q

What are the advantages of cardiac dilation

A

increases resting length (increased preload) which helps maintain SV

D

33
Q

Disadvantage of cardiac dialtion

A

Dilation increases its radius –> will Law of LaPlace, tension in ventricular wall required to generate pressure increases with radisu of the herat

Tension agasint which heart must contract increases with dilation

34
Q

What substrates are utilized by heart (and %) postprandial (after a meal)

A

glucose (40%) and 60% from non-carb (amino acids)

35
Q

As interval after eating …source

A

more from amino acids, less from carbs

36
Q

After prolonged fasting or strenuous exercise , heart sues

A

increases lasma concentration of KETONE BODIEs, whicha re used by heart (

37
Q

When inadequate O2 is delivared to myocardium, heart produces

A

lactic acid from glycogen breakdwn to support aerobic carb metabolism until O2 lack wont allow further metabolism of lactic acid

38
Q

Hypoxic (ischemic) heart

A

dependent on ATP generated from anaerobci metbolism for energy

39
Q

How does blood enter skin

A

skin arterioles can pass through skin capillaries or arteriovenous anastomoses taht direclty connect arteries to veins, byapssign capillaries

40
Q

What is the normal BF rate to skin ? when temp increas?

A

temp is comfortable from 3-5 mL/100g skin

Incresase to 150 mL/100g in hot atomstoshere

41
Q

What controls BF to skin? Which R?

A

sympathetic NS

Adrenergic vasoconsttrictor through alpha-1 receptor

42
Q

Do skin arterioles/BF increases or decreases durign heat?

A

Dilate during heat,

Constrict during cold

43
Q

What happens when extreminiteis expose to severe cole

A

strong vasoconstriction

as hadns and feet reach near freezing, some vasodaltion occurs by relaxation of arteriovenous anastomoses

Vasodilation at expense of lowering core body T

44
Q

Sympathetic cholinergic fibers. What is Bradykinin?

A

induce sweating

Sweat contains Bradykinin- local VASODILATOR

45
Q

What are other vasodilators released during skin injury

A

Histamine, ATP, substance P, bradykinin

46
Q

What receptors are in arterioles of skletal muscle beds

A

mostly Beta-2; respond to epineprhine and dilate

47
Q

How much CO do sk muscle receive at rest?

A

20-25% but b/c large portion of body weight

48
Q

Max exercise, how much CO input

A

90%

49
Q

How much CO does BF to CNS receive

A

cerebral vessels receive nearly 15% of CO although CNS only accts for 2% of body weight

50
Q

Which metabolites creastes increased local production of vasodilators (adenosine, lactic acid, H, CO2 and K) taht reduce cerebral arteriorlar resisteance

A 
Adenosine, 
Lactic Acid
H
CO2 
K
51
Q

Can BF into brain exceed outflow?

A

NO!

52
Q

What happens to BF in brain when flashes of light shined on retinea

A

Increased blood flow to, and metabolism within ,visual cortex

Consequently, flow is decreased in other brain areas

53
Q

Large arteries leading to brain are innervated by

A

SNS but they exhibit myogenic autoregulatio thus brain blood flow is nearly constatn over range of arterial pressures

54
Q

What is “Cushing’s Reflex”

A

Hypothalamic response to cerebral ischemia that consists of and increase in sympathetic tone that increases heart rate, arterial BP, and total periphearl resistance

55
Q

What is the barorR reflex

A

incresing vagal tone and iminishes HR

REsulting combo of hypertensin, bardycardia, and increased pulse pressure seen in response to increased intracranial pressure a rereferred to as Cushing’s reflex

56
Q

How much blood CO (%) does sphlancnic bed receive

A

255

57
Q

What arteries supply splanchnic circuatio

A

celiac,
superior mesenteric
inferior mesenteric arteries to GI tract, spleen ,pancreas, and liver

Portal vein tranpsorts venous blood at low P to the liver

58
Q

What innerveates teh splanchnic circualtion

A

Vagus nerve

predominates during digestion

Can be overcome by sympathetic sysstem whci reduces splanchnic BF`

59
Q

What happens to Instestinal ciculation during hemorrhage or intesnse exercise

A

BF to intensine severely reduced by alpha-mediated vasoconstriction

BF divereted frm Splanchnic bed to central venous system for use by othe rtissues

60
Q

What happens when BF to intestinal mucosa is esp low (hemorrhagic shock)

A

celsl at tipi of villus may become severely hypoxic, even to point of causing necrosis

more permeabl to bacteria and organisms

61
Q

How much CO doe liver receive

A

25%

3/4 deliered by protal vein

1/4 delivered by hepatic artery

Bloodf rom hepatic artery and protal vein mix in liver then flows peripherally between hepatic cells and collects in venules – >coalesce into hepatic veins that feed into inferior vena cava

62
Q

What is pressure in liver vessels compared to inferior vena cava

A

Pressure is only slightly above that of hte inferior vena cava and right atrium

63
Q

What happens to hepatic when cardiac failture

A

Central Venous PRessure may exceed hepatic capilalry pressures

Elevation in hydrostatic P in hepatic interstitium causes exudation of fluid thorgh permeable liver capsule and into bdominal cavity abdominal edema or ascites)

64
Q

What happens to hepatic when cardiac failture

A

Central Venous PRessure may exceed hepatic capilalry pressures

Elevation in hydrostatic P in hepatic interstitium causes exudation of fluid thorgh permeable liver capsule and into bdominal cavity abdominal edema or ascites)

65
Q

How much blood volume in liver. what happens when alpha-adrenergenc innervation

A

15% BV.

Vasoconstriction and reduction in hepatic BF

66
Q

CO of kindey

A

only 1% of body weight ,but receive 20% CO

Physiology Winter 2012 (10 decks)

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