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► Med - Year 1 > Circulation to Special Regions > Flashcards

Circulation to Special Regions Flashcards

1
Q

The “special circulation” with the highest percent

A

pulmonary (100%)

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2
Q

What are the primary resistance vessels of the circulatory system?

A

Small arteries and arterioles

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3
Q

These are the three main extrinsic factors that regulate smooth muscle tone

A
  1. Autonomic Nervous System
  2. Hormones
  3. Cytokines
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4
Q

Cytokines have this BIG effect

A

significant vasodilation —opens up vessels BIG TIME

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5
Q

These are the three main intrinsic/local factors that regulate smooth muscle tone

A
  1. Myogenic mechanisms
  2. Endothelial cell-mediated factors
  3. Metabolic factors
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6
Q

In the sympathetic nervous system, what controls the outflow?

A

The medullary vasomotor center

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7
Q

In the sympathetic nervous system, vasoconstriction is controlled by which adrenoceptor?

A

alpha1

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8
Q

In the sympathetic nervous system, vasodilation is controlled by which adrenoceptor?

A

beta2

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9
Q

What controls the outflow in the parasympathetic nervous system?

A

medullary vasomotor center

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10
Q

Which nervous system sets basal tone of some vascular beds by tonic activation?

A

Sympathetic nervous system

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11
Q

The parasympathetic nervous system generally has little effect in most vascular beds. What are the two exceptions?

A
  1. GI tract (indirect)
  2. Genitalia
    - vasodilation of erectile tissue due to NO release–>activates guanylyl cylcase –> increases cyclic GMP vasodilation
    - sildenafil (viagra): inhibits PDE which is responsible for cGMP hydrolysis
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12
Q

State how these hormonal factors affect vascular tone (i.e dilation or constriction):

  • NO
  • Vasopressin
  • Epinephrine
  • Cytokines
  • Atrial Natriuretic Peptide
  • Angiotensin II
  • Endothelin
  • Bradykinin
A
  • NO = dilation
  • Vasopressin = constriction
  • Epinephrine = high [alpha] (constriction); low [beta1] (dilation)
  • Cytokines = dilation
  • Atrial Natriuretic Peptide (stimulated by atrial stress) = dilation
  • Angiotensin II = constriction
  • Endothelin = constriction
  • Bradykinin = dilation
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13
Q

Two important cytokines. How do they decrease BP?

A

Tumor Necrosis Factor (TNF) and Interleukin 5

-plummet BP by decreasing R (pressure = flow x resistance

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14
Q

When a patient has low cardiac output, these two major players (hormonal factors) are very important for promoting vasoconstriction:

A
  • angiotensin II

- alpha receptors

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15
Q 
Dilation is caused by an increase or decrease in the following metabolic (intrinsic) factors:
\_\_\_ adenosine
\_\_\_ pH
\_\_\_ P(CO2)
\_\_\_ P(O2)
A

dilation caused by:

  • increased adenosine
  • decreased pH (acidic)
  • increased P(CO2)
  • decreased P(O2)
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16
Q

Where is the only place where a decrease in P(O2) causes vasoconstriction instead of dilation?

A

Alveolar P(O2) / lungs.

Paradoxical phenomenon: pulmonary arteries CONSTRICT in presence of hypoxia (low oxygen, such as during pneumonia) without hypercapnia (increased CO2 levels).

  • Constriction leads to redistribution of blood flow to better-ventilated areas of the lung –> increases total area involves in gaseous exchange
  • improves ventilation/perfusion ratio and arterial oxygenation, but less helpful for long-term whole-body hypoxia.
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17
Q

Definition of perfusion and ventilation

A 
perfusion = blood that reaches alveoli
ventilation = air that reaches the alveoli
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18
Q

Overall, how do myogenic mechanisms play a major role in autoregulation?

A

Under various pressures, it attempts to maintain the same flow (called a compensatory response)

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19
Q

Describe the myogenic mechanism for increased pressure:

increased pressure –> (increase/decrease) stretch of vascular smooth muscle cells –> (vasoconstriction/vasodilation)

A

increased pressure will increase the stretch of VSM cells.

Since Pressure = Flow x Resistance, or
Flow = P/R,

the increase in pressure (indicated by increase of stretch) will stimulate vasoconstriction (which will cause an increase in resistance)

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20
Q

When blood vessels constrict, the flow of blood is (increased/decreased), thus (increasing/decreasing) resistance

A

Decreased, increasing

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21
Q

What type of control is most important for cerebral circulation (very sensitive to changes in blood flow)?

A

Intrinsic control–metabolic factors especially important

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22
Q

In the regulation of cerebral blood flow, what range of mean arterial pressure gives you constant flow?

A

Constant from 65-140 mmHg

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23
Q

Name of doctrine that states: The sum intracerebral blood volume + CSF volume + volume taken up by central nervous tissue MUST remain constant because of space limitations imposed by carnium

A

Monro-Kellie Doctrine

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24
Q

Equation for cerebral perfusion pressure:

A

Mean Arterial Pressure - Intracranial Venous Pressure

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25
Q

The systematic circulation is a circuit in (series/parallel). What does this allow?

A

Parallel circuit. Allows variable amount of flow to organs which are not regulated

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26
Q

What can override systemic factors and allow increased flow (i.e. muscle)?

A

Local factors

27
Q

What is extremely important to maintain constant flow over a wide range of pressures? Where is this particularly important?

A

Autoregulation. Very important in the cerebral cortex

28
Q

What are the consequences of increased intracranial pressure?

A

The intracranial pressure compresses the brain vasculature, which will decrease flow DESPITE autoregulatory vasodilation (F = P/R)

29
Q

If there is an increased intracranial pressure, the ischemia (narrowing of vessel/restriction in blood supply to tissue) stimulates the vasomotor center to increase what? What effect will this have?

A

Ischemia calls vasomotor center to tell it to increase systemic resistance! Why? It will increase blood pressure and maintain flow. Known as Cushing’s Reflex

30
Q

Describe Cushing reflex mechanism

A

Increased ICP –> sympathetic response activates alpha1 receptors –> arterial constriction –> increases total resistance of blood flow –> elevates blood pressure (hypertension) –> attempt to restore blood flow

31
Q

In addition to capillaries, what other vessels are involves in heat exchange for apical skin?

A

Arteriovenous anastomoses

32
Q

Are arterioles under the control of local metabolites?

A

No-only sympathetic fibers

33
Q

Sympathetic stimulation can (reduce/increase) blood flow

A

both!
reduce–cold weather, stress
increase–blushing

34
Q

The major function of non-apical skin

A

thermoregulation

35
Q

Changes in skin blood flow are mediated by these two branches of the sympathetic nervous system

A
  1. noradrenergic vasoconstrictors

2. cholinergic active vasodilators

36
Q

Cold exposure causes (vasodilation/vasoconstriction)

A

vasoconstriction

37
Q

How does exercise or heat exposure promote heat loss?

A
  • By activating cholinergic sympathetic vasodilator fibers

- By activating sympathetic cholinergic fibers that innervate sweat glands–promotes sweating and evaporative heat loss

38
Q

If you have someone on a beta blocker, what is one sympathetic symptom that will not be muted?

A

Sweating is not inhibited by the beta receptor blocker–sweat glands contain muscarinic receptors (mAChRs). Sweating can be sign that you’re hypoglycemic

39
Q

A diabetic that is hypoglycemic will activate what response? Effect?

A

Will trigger sympathetic response, heart rate goes up, might get anxious, BP may increase, start sweating.

40
Q

During exercise, what factors dominate, causing what?

A

Intrinsic factors can override extrinsic, leading to vasodilation

41
Q

During exercise, vessels in muscles are vasodilating due to what factors?

A

Local intrinsic factors (metabolic–decrease PO2, increased PCO2, decreased pH, increased adenosine)

42
Q

During exercise, there is a (decreased/increased) venous return. Explain why

A

Increased. Due to muscle contraction and activation of sympathetic nervous system –want to maximize flow to skeletal muscle by increasing CO and also recruitment of capillaries (thus decreasing SVR)

MAP = CO x SVR

43
Q

What is the change in BRAIN blood flow during exercise?

A

There is none due to autoregulation

44
Q

What happens to ejection fraction during exercise? Why?

A

It goes up. LV pumping harder, beta1 increases contractility

45
Q

Why does pulse pressure go up during exercise?

A

Increased stroke volume

46
Q

Why does stroke volume go up during exercise (thus increasing pulse pressure)?

A

Increased filling of ventricles (increased end diastolic volume) and increased contractility

47
Q

Why are arterioles considered the primary vessels involved in regulation of arterial blood pressure and blood flow within the organ?

A

Most highly innervated with autonomic nerves–specifically sympathetic adrenergic. Responds to changes in nerve activity and circulating hormones by constricting or dilating

48
Q

Which vessels have the highest pressure?

A

Aorta and arteries

49
Q

Formal definition of blood pressure

A

measure of force exerted by blood against the walls

50
Q

Poiseuille’s law states that flow decreases when resistance (decreases/increases)

A

Flow decreases when resistance increases

51
Q

As a form of autoregulation, distal prearterioles undergo myogenic (dilation/constriction) if increased pressure

A

constriction. need to keep flow constant! flow = P / R. If P increases, need to increase R to keep flow constant. Increase R by constricting

this maintains constant pressure at the arterioles

52
Q

tachycardia (increases/decreases) time in diastole

A

decreases

53
Q

What are subendocardial coronary vessels?

A

vessels that enter the myocardium

54
Q

When are subendocardial vessels compressed?

A

During systole (contraction of ventricular myocardium) due to high intraventricular pressure

(blood flow in the subendocardium thus stops)

55
Q

When does most myocardial perfusion occur?

A

During diastole (heart relaxation) when the subendocardial coronary vessels are under low pressure

56
Q

Does flow ever come to zero in the right coronary artery? Why or why not?

A

No, since the RV pressure is less than the LV pressure

57
Q

Equation for coronary perfusion pressure to the subendocardium of the LV

A

aortic diastole pressure - any pressure drop across a stenosis - LV end diastolic pressure

58
Q

decrease alveolar P(O2) –> (increase/decrease vasoconstriction

A

increase. shunts blood to better ventilated areas, ventilation/perfusion ratio

59
Q

Splanchnic circulation goes to these 5 main areas

A
  1. stomach
  2. small and large intestines
  3. pancreas
  4. liver
  5. spleen
60
Q

In pulmonary circulation, it is important to match ventilation with _____

A

perfusion

61
Q

In pulmonary circulation, are extrinsic factors more important than intrinsic factors?

A

Intrinsic are more important

  • autoregulation does not occur
  • endothelial cell-mediated factors are important i.e. for inflammation
  • metabolic factors are most important (PO2)
62
Q

After a meal, blood flow (increases/decreases). Explain 2 mechanisms

A

increases (because of nutrition)

  1. increased mucosal activity produces vasodilator substances (adenosine and CO2)
  2. food ingestion causes release of GI hormones (eg cholecystokinin) increases blood flow
63
Q

Increased sympathetic nervous system activity directly (constricts/dilates) splanchnic blood vessels

A

constricts

64
Q

If a patient who exercises a lot has a noted iron deficiency anemia, what could be the cause?

A

The iron deficiency could come from intestinal loss of iron
-GI bleed–when pt exercises, sympathetic levels are so high, causing ischemia to the intestine and thus an iron deficiency

► Med - Year 1 (48 decks)

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