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Human Epithelial Biology > Chemical Control of Breathing > Flashcards

Chemical Control of Breathing Flashcards

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1
Q

What are the sensors involved in the regulation of involuntary breathing rhythm?

A

central chemoreceptors
peripheral chemoreceptors
stretch receptors

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2
Q

What do the central chemoreceptors measure?

A

pCO2 in the CSF via HCO3 at the medula

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3
Q

What do the peripheral chemoreceptors measure?

A

the PO2, PCO2 and pH in the blood and mixed lung gases

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4
Q

What sensors are the peripheral chemoreceptors?

A

carotid body

neuroepithelial bodies

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5
Q

What do the stretch receptors do?

A

Hering-Breuer reflex
inhibit lung over-inflation
increase breathing frequency following rapid lung deflation

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6
Q

Which breathing response can be altered by training?

A

the central chemoreceptors

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7
Q

What has the biggest contribution to normal control of breathing?

A

central chemoreceptors - 80%

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8
Q

What do the central chemoreceptors primarily detect?

A

pH changes caused by increase PaCO2

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9
Q

What do the peripheral chemoreceptors primarily detect?

A

decrease in PaO2 in blood and airway

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10
Q

Which breathing response is fastest?

A

the peripheral chemoreceptors

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11
Q

What cannot cross the blood brain barrier?

A

HCO3 and H

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12
Q

What does high HCO3 cause?

A

reaction reversal

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13
Q

What does the reaction reversal of HCO3 do?

A

creates CO2 which can diffuse in to the CSF where HCO3 is made again

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14
Q

Why is the reaction to HCO3 slower in the brain?

A

there is no carbonic anhydrase

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15
Q

What allows small changes in pH to be detected?

A

there is no pH buffering system in the brain

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16
Q

Where does the signal go from the medulla?

A

increased firing to DRG

17
Q

What change in pACO2 doubles total ventilation?

A

40-45mmHg

18
Q

Why does hypoxia make the response steeper?

A

hypoxia may bring central chemoreceptors closer to firing threshold

19
Q

What causes yawning?

A

relaxation gives pCO2 time to build up slowly overtime…yawn is a reboot through the CCR

20
Q

What may be used to overide the CCR response?

A

narcotics

21
Q

What is the adaptive ability of CCRs relevant to?

A

disease
high altitude
free diving
drug action

22
Q

How do free divers end up in shallow water black out?

A

hyperventilation drives initial pACO2 down
O2 consumed during dive
low CCR sensitivity due to training
fails to trigger breathing response in time to prevent severe hypoaemia
loss of conciousness

23
Q

What are the peripheral chemoreceptors?

A

the carotid body - carotid sinus
aortic body - aortic arch
neuroepithelial bodies

24
Q

What is the issue with peripheral CRs?

A

they are only located in the arterial system and so cannot detect metabolic perturbations during exercise

25
Q

What is likely to have the biggest influence on breathing patterns during exercise?

A

conscious control

26
Q

When will peripheral chemoreceptors influence breathing?

A

only if arterial pO2 falls such as exercise with hypoxia or hypoxic respiratory diseases

27
Q

What do PCRs do at altitude?

A

act to maintain alveolar pO2 closer to inspired pO2

28
Q

What do PCRs respond to?

A

primarily hypoxia but because of the Bohr-Haldane effects also the pH and PaCO2

29
Q

Why are PCRs not in the venous vasculature?

A

they are an emergency response

30
Q

How can you get the rate of ventilation per litre of oxygen consumed?

A

Dividing ventilation rate per minute by oxygen consumption

31
Q

Why is breathing at altitude exhausting?

A

there are more breaths per ml of O2 consumed

32
Q

What happens to the work of breathing at altitude?

A

it utilises almost all the O2 consumed hence need suplementary oxygen

33
Q

How does the cell transmit hypoxia signals?

A

depolarises the cell through O2 or pH sensor
Opens VGCC
NT release
Glossopharyngeal nerve goes to DRG and RRG

34
Q

What are the responses of the brain stem?

A

hypoxic ventilatory response

hypoxic pulmonary vasoconstrictor response

35
Q

What channels sense O2 and pH levels?

A

TASK 3 K+ channels

36
Q

What is the effect of O2 and hypoxia on the TASK channel?

A

closes the channel - both proton and hypoxia create a larger effect

37
Q

How does acidosis cause closure ?

A

acidifcation of the cytosol stimulates closure of a hinge-like loop across the pore of the channel

38
Q

How does hypoxia stimulate closure?

A

suppressing the rate at which IC superoxide is made by NADPH oxidase - which normally prevents hinge loop from closing

Human Epithelial Biology (20 decks)

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