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acid base control of respiration Flashcards

1
Q

what is the choroid plexus?

A

specialised tissue in the ventricles of the brain that has capillaries which allow water and ions to pass out to form CSF

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2
Q

where are the central chemoreceptors found?

A

ventral surface of the medulla

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3
Q

how do central chemoreceptors sense pH?

A

use specialised neutrons to detect the pH of the CSF

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4
Q

why is the CSF a good indicator of blood acidity?

A

CO2 from the blood moves across the BBB into the CSF and forms carbonic acid which is then converted into protons and bicarbonate by carbonic anhydrase

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5
Q

how do central chemoreceptors lead to a higher blood pH?

A

detect increased acidity of the CSF
stimulate neurons in the respiratory control centre to increase ventilation
expels CO2
less CO2 in the blood and the CSF

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6
Q

what is the normal pH of the CSF?

A

7.32

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7
Q

why is the change in pH in the CSF for a certain PCO2 greater than in the blood?

A

no plasma proteins are filtered through the choroid plexus so the CSF has no proteins
lack of protein means it has much less pH buffering capacity than the blood

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8
Q

what effect does chronic pulmonary disease have on central chemoreceptors?

A

causes the central chemoreceptors to gradually become less sensitive over time bc there are chronically high CO2 levels
drive for ventilation from CO2 is reduced

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9
Q

what are the type of lung based respiratory stretch receptors?

A

pulmonary stretch receptors
irritant receptors
J receptors

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10
Q

where are pulmonary stretch receptors found?

A

bronchioles and small bronchi

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11
Q

what is the function of pulmonary stretch receptors?

A

carry out the Hering-Breuer inflation reflex

inhibit inspiration when the lungs are fully inflated to prevent damage to the lung tissue from overinflation

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12
Q

how do pulmonary stretch receptors inhibit inhalation?

A

send APs through afferents in the vagus nerve to the respiratory centres in the pons and medulla

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13
Q

what is the Hering-Breuer inflation reflex?

A

inhibition of inspiration

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14
Q

what type of receptors are irritant receptors?

A

mechanoreceptors

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15
Q

where are irritant receptors found?

A

in the lining of the trachea and large bronchi

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16
Q

what do irritant receptors do?

A

detect the presence of objects in the airway that are too large to be carried away by mucus
activate the cough reflex

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17
Q

what type of receptors are J receptors?

A

chemoreceptors

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18
Q

what do J receptors do?

A

stimulate an increase in ventilation and respiration

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19
Q

what do J receptors respond to?

A

events such as pulmonary edema, pulmonary emboli, pneumonia, and barotrauma, which cause a decrease in oxygenation

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20
Q

where are irritant receptors found?

A

in between airway epithelial cells

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21
Q

where are J receptors found?

A

in the alveoli

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22
Q

how do J receptors cause an increase in respiration rate?

A

send afferent signals via the vagus to increase respiration rate

23
Q

describe the relationship between ventilation response and raised arterial pCO2

A

linear relationship

24
Q

what increases sensitivity to CO2?

A

hypoxia

25
Q

what is hypercapnia?

A

increased CO2

26
Q

what is the main chemical drive to ventilation?

A

hypercapnia

27
Q

what is the relationship between hypoxia and hypercapnia?

A

hypoxia increases the sensitivity of the respiratory centres to hypercapnia

28
Q

when does hypoxia on its own stimulate breathing?

A

when the PO2 is less than 60mmHg

29
Q

what are the sensors for hypoxia?

A

peripheral chemoreceptors

30
Q

where are peripheral chemoreceptors found?

A

in or around the carotid bodies at the bifurcation of the common carotid arteries
aortic bodies above and below the aortic arch

31
Q

what is the most heavily vascularised tissue in the human body?

A

the carotid body

32
Q

what do the afferent nerves of peripheral chemoreceptors respond to?

A

hypoxia and plasma pH

lowkey respond to hypercapnia

33
Q

how do afferents from peripheral chemoreceptors travel to the brainstem?

A

in the glossopharyngeal nerve

some may travel in the vagus

34
Q

what cells make up the carotid body?

A

glomus type 1 cells - chief cells

glomus type 2 cells - sustenacular cells

35
Q

where are glomus type 1 cells derived from?

A

neuroectoderm

36
Q

what do glomus type 1 cells do?

A

release neurotransmitters that stimulate the sensory endings of the vagus and glossopharyngeal afferent nerves that project to the medullary respiratory centres

37
Q

what is the function of glomus type 2 cells?

A

resemble glia and act as supporting cells

38
Q

what do type 1 glomus cells detect?

A

hypoxia

39
Q

how do glomus type 1 cells detect hypoxia?

A

Hypoxia inhibits K+ channels
Inward leak of Na+ –> depolarization –> opening of Ca2+ channels –> release of NTS e.g. ACh –> cause action potentials which travel up to the respiratory centres

40
Q

what makes up the respiratory centres?

A

3 main groups of neurons located in the pons and medulla of the brainstem
main one is in the medulla which projects down reticulospinal tract to activate diaphragm

41
Q

where does the reticulospinal tract originate?

A

in the pons and medulla

42
Q

where does the reticulospinal tract descend?

A

down the spinal cord around the margin of the ventral horn

43
Q

what provides the only motor innervation to the diaphragm?

A

the phrenic nerve

44
Q

where does the phrenic nerve arise?

A

in the neck from C3-C5

45
Q

what does the nucleus of the solitary tract receive innervation from?

A

pH receptors,
pulmonary stretch receptors
cough receptors
J receptors

46
Q

where is the NTS found?

A

dorsal surface of the medulla

47
Q

where does the NTS project to?

A

to the dorsal respiratory group which contain cells that fire during inspiration

48
Q

which neurones become active during forced expiration and what do they do?

A

neurons in the ventral respiratory group in the ventral medulla
axons project down the reticulospinal tract and activate the internal intercostals

49
Q

what modulates the intrinsic rhythm of the dorsal respiratory group?

A

Apneustic center (makes inspiration last longer)

Pneumotaxic center (inhibits apneustic center)

50
Q

what does the apneustic centre do?

A

makes inspiration last longer - how we can hold our breath

51
Q

what does the pneumotaxic centre do?

A

inhibits the apneustic centre, thus decreasing tidal volume and respiratory rate

52
Q

how is breathing for vocalisation regulated?

A

cerebral cortex acts via the penumotaxic and apneustic centres

53
Q

what is Cheyne-Stokes breathing?

A

damage to sensory input = gradual increase in depth/rate of breathing, followed by gradual decrease called apnoea

54
Q

when is Cheyne-Stokes breathing seen?

A

strokes

heart failure

c (25 decks)

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