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CR 2 > NO in cardiovascular system > Flashcards

NO in cardiovascular system Flashcards

1
Q

What conversion reaction forms nitric oxide

A

L-arginine–> citrulline

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2
Q

What enzyme is used to form nitric oxide

A

Nitric oxide synthase

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3
Q

Apart from the enzyme, what else is required for synthesis of nitric oxide

A

Oxygen

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4
Q

Name 3 relevant isoforms of nitric oxide

A

Type 1= brain NOS= bNOS
Type 2= iNOS
Type 3= endothelialNOS= eNOS

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5
Q

Which 2 isoforms of NO are most closely related

A

bNOS and eNOS

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6
Q

Which 2 isoforms of NO are calcium dependent

A

bNOS and eNOS

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7
Q

What cells use bNOS

A

central and peripheral neuronal cells

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8
Q

What cells use iNOS

A

Most nucleated cells especially macrophages

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9
Q

What cells use eNOS

A

Vascular and endothelial cells

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10
Q

What is the main regulatory factors in NO synthesis

A

flowing blood

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11
Q

How does flowing blood activate NO synthesis

A
  • Shear stress of endothelial wall causes opening of Ca2+ channels allowing calcium into endothelium
  • This activates calmodulin
  • This activates eNOS
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12
Q

What cofactors are required in the synthesis of NO

A

H4, FMN and FAD

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13
Q

How can acetylcholine activate NO

A

Binds to Ach receptor on endothelium

Allows calcium entry

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14
Q

How does NO work to stop cell contractions

A
  • NO diffuses into surrounding smooth muscle
  • Activates guanylate cyclase
  • This converts guanosine triphosphate– cyclic guanosine monophosphate
  • This removes calcium and open potassium channels
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15
Q

Main 2 functions of NO

A
  • Relaxes and dilates anterior smooth muscle lowering vascular resistance
  • Prevents unwanted intravascular coagulation opposes effect of noradrenaline and angiotensin
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16
Q

How does eNOS aid in gas exchange between haemoglobin and cells

A

NO released from vascular endothelium during period of local hypoxia, diffuses into blood as well as smooth muscle
In red cells, reacts with oxyhaemoglobin to form nitrosohaemoglobin
Displaces oxygen from haemoglobin improving delivery of o2 to hypoxic tissues

17
Q

How is blood redistribution achieved during exercise

A

Sympathetic nervous system causes systemic vasoconstriction
Exercising muscles release local dilators which can overcome constriction
Therefore exercising muscles dilated and inactive ones constricted

18
Q

What local vasodilators are used by exercising muscles during exercise

A

NO and adenosine

19
Q

What triggers vasodilation during exercise

A

Lactic acid causes acidosis

20
Q

What is the effect of acidosis on coronary circulation

A

Diameter of coronary arteries and number of open arterioles (collaterals)

21
Q

Can NO be synthesised in hypoxic tissues

A

No- requires oxygen

22
Q

In what form is NO stored when not immediately needed

A

Nitrite (NO2)

23
Q

What 2 equations allow storage on NO as nitrite

A

NO+ H20—> HNO2 + H+ + e-

HNO2—» H+ + NO2

24
Q

Where does the first equation that allows conversion of NO to nitrite occur

A

Pulmonary venous blood

25
Q

When is nitrite converted back to NO

A

Hypoxic conditions

26
Q

What is glycerol trinitrate used for? Brief mechanism

A

Drug used for heart attacks

Nitrite to NO

27
Q

What effect does NO have on pulmonary arterial pressure

A

Low

28
Q

What is effect of NO on the lungs during hypoxia

A

Production of NO reduced- constriction

29
Q

How does cardiac output change during exercise

A

3 fold increase

30
Q

How is increase of pulmonary blood flow during exercise achieved

A

Decreasing pulmonary resistance because distension of thin arteriolar walls leads to more NO synthesis
Also relaxation of bronchial smooth muscle by B2 receptors

31
Q

How does NO aid in anticoagulation

A

NO release from vascular endothelium preventing adhesion of leukocytes and platelets

CR 2 (33 decks)

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