pk 9 - Sensory Modulation of Respiration

Question 1

What are the major chemoreceptors in the body?
What do they respond to?
Where are they located?

Answer 1

carotid bodies
changes in arterial blood gas tensions and pH
located at bifurcation of common carotid artery (C4)

Question 2

The carotid bodies can detect changes in ………, play a major role in detecting ……… acid-base disturbances and are the site of the body’s major receptors for detecting systemic ………….

Answer 2

PaCO2
metabolic
hypoxia

Question 3

Where are the other chemoreceptors located?

Answer 3

aortic bodies

arch of the aorta

Question 4

What is the afferent innervation of the carotid and aortic bodies?

Answer 4

carotid = glossopharyngeal
aortic = vagus

Question 5

What are the aortic and carotid sinuses?

Answer 5

location of baroreceptors
not distinct organ
share same afferent nerves as the bodies

Question 6

What cells make up the carotid body?

Answer 6

Type 1 carotid body cell - glomus cells

Question 7

The carotid bodies show a …… and ……. response to hypoxia

Answer 7

rapid

graded

Question 8

Describe the hypoxia sensing mechanism that takes place in the gloms cells of the carotid body x7

Answer 8

1. hypoxia inhibts oxidative phosphorylation
2. This increases AMP/ATP ratio
3. This activates AMPK
4. This inhibits BK/TASK K+ channels
5. This leads to membrane depolarisation
6. This opens voltage-gated calcium channels
7. Neurosecretion

Question 9

The carotid body accounts for of the ………… response to a change in ……..
The carotid body fires at normal PaO2. Without the carotid body Ve would ……… by 15%

Answer 9

ventilatory
PO2
fall

Question 10

What shape is a graph showing the carotid bodies response to hypoxia?
How does the curve shift in acidosis? Why?

Answer 10

hyperbolic

shifts right and upwards as discharge is higher when blood is more acidic or PaCO2 is raised

Question 11

What is a carotid tumour a response to?

Answer 11

low O2

Question 12

The precise location of central chemoreceptors is not yet fully elucidated, but they are known to be located near the ……… ………. of the ……….

Answer 12

ventral surface of the medulla

Question 13

Central chemoreceptors respond relatively …….. to change in ……. …. which can be altered primarily by changes in ………. . The …….. prevents significant changes in CSF pH due to ………….. changes in acid-base status

Answer 13

slowly
CSF pH
PaCO2
BBB
metabolic

Question 14

Acclimatisation to chronic changes in CSF pH will ……. the stimulus and hence the response - and could occur via an as yet undefined mechanism, which could be a ………… transporter

Answer 14

reduce

bicarbonate

Question 15

The ventilatory response to changes in PaCO2 and PaO2 are …………. and can also be affected by …………… and …………..

Answer 15

multiplicative
anaesthesia
exercise

Question 16

What are the 3 pulmonary mechanical receptors?
Describe what each detects and the response generated.
What are they are innervated by?

Answer 16

1. Rapidly adapting irritant receptors, detect sudden lung distention and certain irritants, cause cough, bronchoconstriction, hyperpnea
2. Slowly adapting stretch receptors, activated by lung distention, inhibit inspiration and promote expiration, bronchodilation and tachycardia
3. J-type (Juxtacapillary) or C Fibre Receptors
   all innervated by the vagus, activated by interstitial fluid, cause apnoea, bronchoconstriction, increased mucus, hypotension, bradycardia, contribute to breathlessness in left heart failure