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CR2 > 37 - Nitric Oxide in the Vascular System > Flashcards

37 - Nitric Oxide in the Vascular System Flashcards

1
Q

What releases nitric oxide

A

GTN (Nitroglygerin)

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2
Q

Function of NO

A

Smooth muscle relaxation –> vasodilateion

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3
Q

What is EDRF

A

Nitric oxide

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4
Q

What can nitrous oxide be used for

A

Laughing gas

medication

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5
Q

What is entonox

A

Nitrous oxide 50%
Oxygen 50%
N20

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6
Q

What is entonox used for

A

Medical anaesthesia gas used in childbirth and emergency medicine

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7
Q

What does nitric oxide synthase od

A

NOS converts L-arginine —-> citrulline + NO using oxygen

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8
Q

isoforms of NOS

A

1) Brain
2) Macrophages
3) Vascular endothelium

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9
Q

What controls brain isoform of NOS

A

Intracellular calcium

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10
Q

What controls Macrophage isoform of NOS

A
  • cytokines
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11
Q

What controls vascular endothelim isoform of NOS

A

Calcium

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12
Q

What causes synthesis of NO

A

Shear stress on wall caused by friction opens calcium channels –> calcium enters endothelial cells –> calmodulin activated by calcium –> activates eNOS

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13
Q

Co-factors required for NO synthesis

A

Biopterin H4
FMN
FAD
ACh, bradykinin, substance P - causes calcium to enter

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14
Q

What occurs when NO diffuses from endothelium to SM

A

NO activates guanylate cyclase

Converts GTP to cGMP

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15
Q

What does cGMP d

A

Makes smooth muscle relax - vasodilation to increase local blood flow

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16
Q

What do drugs inhibiting eNOS cause

A

Increase in resting BP

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17
Q

What does NO maintain

A

Normal BP

Low peripheral resistance

18
Q

Function of NO in vascular system

A

Relaxes and dilates arteriolar smooth muscle

Prevents unwanted intravascular coagulation - Nitroglycerin –> NO

19
Q

NO function in hypoxia

A

Aids in gas exchange between Hb and cells
into RBC –> reacts with oxyhaemoglobin –> nitroxyhaemoglobin which displaces oxygen from Hb and improves the delivery of oxygen to the hypoxic tissue

20
Q

How does blood flow during exercise change to muscle, heart, kidnet, skin and brain

A 
o	Muscle x10
o	Heart x3 
o	Kidney /2
o	Skin x4 
o	Brain blood flow does not change
21
Q

Cause of muscle blood flow changes during exercise

A

1) Vasoconstricion inactive muscle

2) Vasodilation in active muscle

22
Q

What mediates vasoconstriction of arterioles

A

Alpha-1 receptors

23
Q

Local vasodilators

A

NO

Adenosine

24
Q

How is oxygen produced for NO synthesis in hypoxia (exercising)

A

Anaerobic resp –> lactate produced –> low pH converts nitrite –> HNO2 (nitrous acid) –> converted to NO using electron from ascorbic acid a reducing agent –> provides oxygen for later synthesis

25
Q

eNOS activity in angina

A

Angina endothelium damaged –> eNOS reduced –> less dilation during exercise –> hypoxia –> Acidosis

26
Q

What is persistant pulmonary hypertension of the Newborn

A

No reduction in pulmonary arterial resistance after first breath
Hypoxia - lungs not perfused
NO can be given to save

27
Q

What causes decrease in pulmonary resistance with the first breath

A

Raises po2 in lungs –> NO synthesis –> relaxation of pulmonary vsmc –> dec PAR

28
Q

Link between ventilation and perfusion

A 
Low ventilation (PO2)
Hypoxic constriction due to lack of NO (cannot be synthesised)
29
Q

How much does cardiac output and pulmonary arterial pressure increase in exercise

A

CO - 3X
PAP - slightly
Resistance decreases (Diameter increases)

30
Q

Why does diameter of arteries increase in exercise

A

Sympathetic activation of B2 receptors on bronchial smooth muscles
greater tidal volume - inc o2 conc

31
Q

What affects brain blood flow

A

pH

Hypertension –> Low pCO2 –> alkaline blood –> reduces cerebral blood flow –> confusion and dizziness

32
Q

What does acidity in the brain cause

A

Increase in blood flow to the brain

33
Q

Resting brain blood flow

A

50ml/min/100gm

34
Q

When reversible brain damage due to low blood flow

A

25ml/min/100g

35
Q

When permanent brain damage

A

1/4 of resting brain blood flow

36
Q

How does nitric oxide cause anticoagulation

A

Prevents leukocytes and platelets from adhering to the endothelium

37
Q

What does low blood flow in veins cause

A

AFIB

DVT

38
Q

Function of iNOS

A

Inducible NOS
- Induced by bacteria/toxins
Triggers toxic free radicals in the bacteria

39
Q

Overproduction of iNOS

A

Uncontrolled local vasodilation - septic shock (organ failure and death)

40
Q

Characteristics of SIR (Systemic inflammatory Response)

A 
Fever
Tachycardia
Tachypnea
Increased WBC
(sepsis is SIR caused by infection)
41
Q

Why is NO janus molecule

A

Good and bad points

CR2 (34 decks)

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