22 - modulation of breathing

Question 1

what 3 things do chemoreceptors respond to?

Answer 1

PO2, PCO2, and pH

Question 2

Where are the carotid bodies located?

Answer 2

in the bifurcation of the common carotid artery into the external and internal carotid arteries

Question 3

What are the aortic and carotid bodies innervated by?

Answer 3

aortic - Vagus nerve

carotid - glossopharyngeal

Question 4

Where are aortic bodies located?

Answer 4

in the aortic arch?

Question 5

What are the similarities between aortic and carotid bodies?

Answer 5

they share the same afferents and are near their respective sinuses

Question 6

What are in the carotid and aortic sinuses?

Answer 6

baroreceptors, they share heir innervation with the respective chemoreceptors

Question 7

What is the carotid body made of?

Answer 7

glomus cells

Question 8

What happens when there is a fall in oxygen?

Answer 8

AP’s go haywaire

there is a graded response of hypoxia

Question 9

What does the carotid body contribute to ventilatory responses?

Answer 9

all ventialtory response to PO2 changes

it is also stimulated by metabolic acidosis

contributes 20% of the response to CO2

Question 10

What is the relationship between PaO2 and chemoafferent discharde frequency?

Answer 10

higher PaO2, lower chemoafferent discharge frequency, this relationshiip is a hyperbolic function

Question 11

What effect does metabolic acidosis have on the stimulus response curve of the carotid body?

Answer 11

shifts it up and right

basically increases the amount of discharge for any given level of oxygen

Question 12

How does hypoxia lead to neurosecretion?

Answer 12

reduces ATP production
AMP increases
activation of AMPK
inhibits BK / TASK K+, inhibiting K+ efflux
membrane depolarisation
Ca2+ influx through opened VGC's
neurosecretion

Question 13

What happens to the carotid body in its’ response to hypoxia?

Answer 13

gets bigger, hyperplasia, hypertrophy

this can be useful at altitude
but it can cause a benign carotid body tumour

Question 14

Which areas of the brain are associated with central chemoreceptors?

Answer 14

ventral medulla:

rostral zone, intermmediate zone, caudal zone, all around the basilar artery

Question 15

What proportion of the ventilatory response to CO2 is provided for by central chemoreceptors?

Do they respond to Hypoxia?

Answer 15

80%

No, but they are inhibited by it

Question 16

What lies between the neurones of central chemoreceptors and the blood?

How can central chemoreceptors still be stimulated?

Answer 16

BBB

stops H+ from crossing, so CO2 crosses and then forms H+ instead

Question 17

How do central chemoreceptors acclimatise?

Answer 17

in extended periods of adverse alkalosis / acidosis, the pH is gradually attenuated by active transport of HCO3- from blood to ECF / CSF or other way round

Question 18

Is CCR acclimatisation fast?

Why?

Answer 18

the BB makes it a slow response

Question 19

What happens to patients with chronic lung disease and their attentuation?

Answer 19

they have an attenuated ability to increase ventilation in a high CO2

Question 20

What is the relationship between arterial blood pH and CSF steady state pH?

Answer 20

linear relationship, an increase in arterial pH will see an increase in CSF steady state pH

Question 21

Which of variations in PaCO2 and H+ changes unrelated to ventilation, have a greater effect on CSF steady state pH over a given arterial pH change?

Answer 21

acid-base changes due to variations in PaCO2

Question 22

What effect will CSF pH have on ventilation?

Answer 22

an increase in CSF pH will decrease ventilation

Question 23

What is the relationship betweenPaCO2 and alveolar ventilation?

Answer 23

linear response curve (but steep!!!! so big increases in ventilation for small PaCO2 increments)

Question 24

How does the relationship between PaCO2 and alveolar ventilation change with:
low PaO2
High PaO2 or anaesthesia?

Answer 24

low - steeper line shifted left

high / A - smaller gradient shifted right

Question 25

what is dyspoea?

Answer 25

shortness of breath

Question 26

What is the common afferent between all 3 of pulmonary mechanical receptor?

Answer 26

Vagus nerve to DRG

Question 27

What are the 3 types of pulmonary mechanical receptors?

Answer 27

rapidly adapting irritant receptors
slowly adapting stretch receptors
J type (Juxtacapillary) or C-type fibres

Question 28

Where are rapidly adapting irritant receptors, what are they activated by, and what do they stimulate?

Answer 28

between airway epithelia (large airway)
activated by sudden lung distension and certain irritants
cause cough, bronchoconstriction, and hyperpnea

Question 29

What is the character of the signal sent by RAIR’s?

Answer 29

rapidly adapting within 1s of response, decrease in discharge over time

Question 30

Where are slowly adapting stretch receptors located, what are they activated by, and what do they stimulate?

Answer 30

between smooth muscle cells in trachea and lower airway
activated by lung distention
Hering Breuer reflex, bronchodilation and tachycardia

Question 31

What is the Hering breuer reflex?

What significance does it have for humas?

Answer 31

inhibtion of inspiration and promotion of expiration

if you rapidly inspire it’s terminated quite quickly by this reflex
younger humans have a greater reflex, implying it’s a defence mechanism (cortical development may take over)

Question 32

What is the character of the signal sent by SASR’s?

Answer 32

slowly adapting, so the firing rate is sustained during the stretch

Question 33

Where are J type fibres, what to the sense, and what do they stimulate?

Answer 33

terminals on alveoli and pulmonary capillaries

activated by interstitial fluid, pulmonary congestion, oedema

they cause apnoea, bronchocontriction, increases mucus secretion, hypotension, bradycardia

Question 34

What is the characteristic of the signal sent by J-type fibres?

Answer 34

rapidly adapting (to change), but slowly conducting as they are C-type