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Lungs > control of breathin > Flashcards

control of breathin Flashcards

1
Q

what is the central control of breathing?

A

the brain stem

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2
Q

what occurs in the brainstem?

A

normal automatic control of breathing

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3
Q

what can override this + when?

A

the brain’ cortex when voluntary control is desired

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4
Q

what generates the respiratory rhythm?

A

medulla

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5
Q

what is the brainstem?

A

posterior part of the brain, continuous with the spinal cord

consists of the midbrain, pons and medulla oblongata of the hindbrain

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6
Q

experiment to deduce the various functions

A

sectioning of the brainstem above the respiratory centre of the medulla abolishes voluntary, cortical control of breathing but leaves normal rhythmicity intact

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7
Q

different groups of motor neurone in the brain

A

dorsal respiratory group and ventral respiratory group

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8
Q

explain dorsal respiratory group

A

motor neurones associated with initiating inspiration found in the ventrolateral region of the medulla

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9
Q

explain ventral respiratory group

A

upper motor neurones responsible for inspiration and expiration, found in the dorsomedial region of the medulla

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10
Q

what property do these cells have?

A

intrinsic periodic firing, where repetitive bursts of Abs are exhibited that correspond to the rhythm of the ventilatory cycle

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11
Q

what is the function of the pons?

A

fine tuning of the intrinsic respiratory rhythm created by the medulla

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12
Q

major output of nerves from the brain stem

A

phrenic nerves to the diaphragm

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13
Q

what other parts of the brain can alter breathing + when?

A

limbic system, hypothalamus during moments of rage and high emotional states

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14
Q

what considerations must the body consider when regulating breathing?

A
  1. want to breathe enough to ensure Hb gets close to full saturation
  2. don’t want to breathe more than is necessary, waste of effort
  3. want to regulate carbon dioxide quite carefully since variations in CO2 vary pH and small variations in pH can alter physiological function quite widely
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15
Q

what detects changes of pH in the blood?

A

chemoreceptors

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16
Q

Chemoreceptors definition

A

receptors that respond to a change in the chemical composition of the blood or fluid around it

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17
Q

two types of chemoreceptors

A

central and peripheral

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18
Q

where are the central chemoreceptors found?

A

anteriorly superficial to the medulla surface

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19
Q

what do the central chemoreceptors react to?

A

the composition of blood and the CSF

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20
Q

What is the major determinant of pH in the brain + why?

A

carbon dioxide, as the blood brain barrier is relatively impermeable to HCO3- and H+ whereas CO2 can diffuse easily.

when blood CO2 uses it diffuses into the CSF from cerebral blood vessels and liberates H+ ions that stimulate the chemoreceptors

CSF contains very little protein, so has a lower buffering capacity than the blood, so a change in pH of the CSF for a given PCO2 is much greater

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21
Q

how do central chemoreceptors respond to a fall in pH?

A

increase the frequency of action potentials in their afferent nerves, which regulate the activity of the medullary respiratory centre

this causes an increase in ventilatory rate and subsequent decrease in PCO2

22
Q

what is the respiratory centre + location?

A

three major respiratory groups of neurones, two in the medulla and one in the pons

responsible for generating and maintaining the rhythm of respiration and also adjusting the homeostatic response to physiological changes

23
Q

where are peripheral chemoreceptors located?

A

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

24
Q

what innervates the carotid bodies?

A

sinus nerve, a branch of the glossopharyngeal nerve IX cranial nerve

25
Q

which body has mainly respiratory effects? + what does the other have?

A

carotid, aortic bodies mainly vascular effects

26
Q

structure of the carotid body + functions

A

glomus type 1 cells- peripheral chemoreceptors derived from neural crest cells, release neurotransmitter such as ACh ATP and dopamine that trigger EPSPs in synapsed neurones leading to the respiratory centre

glomus type 2- resemble glial cells and act as supporting cells

responsible for all increases in ventilation that occurs in humans response to arterial hypoxemia

27
Q

what do the carotid bodies detect?

A

sensitive to changes in PO2 in arterial blood, specifically decreases

28
Q

action potential production in carotid bodies

A

decrease in oxygen partial pressure leads to the depolarosation of the cell membrane by blocking potassium currents

reduction in membrane potential opens voltage gated calcium channels which causes a rise in intracellular calcium concentration leading to the release of neurotransmitter containing vesicles

29
Q

explain relay of the AP

A

feedback from the carotid body is sent to the cardiorespiratory centres in the medulla oblongata via afferent branches of the glossopharyngeal nerve

efferent fibres from the aortic body chemoreceptors are relayed by the vagus nerve

30
Q

innervation of aortic bodies

A

vagus nerve X

31
Q

stimuli of aortic bodies

A

decrease in PO2, increase in CO2

do not respond to changes in pH

32
Q

when are the various receptors sensitive to concentrations of oxygen?

A

peripheral cells are relatively insensitive to changes in PO2 above 100mmHg, as shown by limited firing of the afferent nerves

below 100mmHg the firing rate greatly increases

at low CO2, the body does not really recognise the PO2

33
Q

when are the various receptors sensitive to concentrations of carbon dioxide?

A

at high PO2 there is still a good CO2 response through central chemoreceptors

34
Q

different degrees of importance of central vs peripheral chemoreceptors explained

A

less than 20% of the ventilatory response can be attributed to the peripheral chemoreceptors when there is an increase in CO2

however there is a more rapid response and so may be useful in matching ventilation to abrupt changes in PCO2

35
Q

result of removing peripheral chemoreceptors

A

removing carotid bodies was a treatment for asthma

individuals may lose carotid bodies following vascular surgery

PAco2 will settle 0.5 kPa higher than normal

no sensitivity to hypoxia

animals without carotid bodies at altitude often become sick and die

36
Q

effect of increased ventilation on alveolar pressures

A

PaO2 increased, PaCO2 decreased

37
Q

where are pulmonary stretch receptors located?

A

lie within airway smooth muscle and discharge in response to distention of the lung

38
Q

innervation of pulmonary stretch receptors

A

impulses travel in the vagus nerve via large myelinated fibres to the medulla and apneustic centre of the pons, resulting in the inhibition of inhalation

39
Q

what is the main reflex that stimulates these receptors?

A

Herring-Breuer reflex

40
Q

explain the Herring-Breuer reflex

A

describes the inhibition of inspiration as the lungs are stretched, with the receptors slowing respiratory frequency due to an increase in expiratory time

prevents the over inflation of the lung

41
Q

what other functions of pulmonary stretch receptors?

A

determine the rate and depth of breathing where tidal volumes exceed 1L like in exercise

bronchodilation by relaxing smooth muscle

42
Q

2 other receptors in lungs

A

irritant receptors and juxtacapillary receptors

43
Q

explain irritant receptors

A

lie between the airway epithelial cells in the nasal mucosa

small myelinated fibres within vagus

respond to stretch and irritants within airways

reflex effects, cough, bronchoconstriction and tachypnoea

44
Q

explain J receptors

A

they re the endings of non-myelinated C vagus fibres found in the lung interstitium

respond if the lungs become congested- stimulated by oedema, act as a visceral pain receptor

believed to be located in the alveolar walls close to the capillaries

responses include rapid, shallow breathing, apnea

45
Q

innervation of bronchi

A

autonomic, from the pulmonary branches of the vagus nerve

46
Q

upper airway obstruction definition

A

the blockage of any portion of the airway above the thoracic inlet

47
Q

presentation of a patient with upper airway obstruction

A

drooling, swelling of face and tongue, wheezing, choking, unconsciousness,

48
Q

lower airway obstruction definition

A

obstruction at the level of trachea, bronchi and bronchioles

49
Q

consequences of obstruction

A

fatal in a matter of minutes

respiratory failure, arrhythmia and cardiac arrest

inflammation of airway walls or lung abscesses

50
Q

relief of obstruction

A

removing foreign body, intubation below the body, tracheotomy and cricothyrotomy

51
Q

how does foreign body aspiration occur?

A

body too large enters the trachea and becomes lodged

52
Q

how does foreign body aspiration occur?

A

body too large enters the trachea and becomes lodged

body in mouth then strong inhalation makes it move into the trachea not the oesophagus

Lungs (10 decks)

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