Control of Breathing

Question 1

what is breathing modulated by?

Answer 1

reflexes, volitional control, vocalisation, emotional events, physiological challenges

Question 2

what must the neuronal control of breathing do?

Answer 2

establish automatic rhythm, respond to metabolic demands, respond to mechanical changes, range of episodic nonventilatory behaviours

Question 3

what is eupnea?

Answer 3

normal rhythmic breathing

Question 4

what is dyspnea?

Answer 4

being short of breath, unpleasant conscious awareness of difficulty breathing

Question 5

what are the respiratory related neurons and what do they do?

Answer 5

array of interconnected neurons and they fire more action potentials during respiratory cycle

Question 6

where is the central pattern generator and what does it do?

Answer 6

in the brainstem (medulla oblongata) and it independently generates respiratory rhythm

Question 7

what do the respiratory motor neurons do?

Answer 7

innervate respiratory muscles, axons via the phrenic nerve innervate the diaphragm

Question 8

what does the frequency of respiratory central pattern generator changes do?

Answer 8

strength of drive from central and peripheral receptors, change both depth and frequency of ventilation

Question 9

what does the brain receive neural signals from?

Answer 9

chemoreceptors (feedback on blood PO2, PCO2 and pH) and mechanoreceptors (feedback on mechanical status of lungs, chest wall and airways)

Question 10

what does the brain send neural signals to?

Answer 10

respiratory muscles (produce rhythmic breathing movements), upper airway muscles and produce reflexes to keep airways patent

Question 11

what are chemoreceptors?

Answer 11

sensory receptors that detect chemical changes in the surrounding environment

Question 12

what do chemoreceptors detect changes in with the blood?

Answer 12

PO2, PCO2 and pH

Question 13

what are peripheral chemoreceptors?

Answer 13

small, highly vascularised bodies in region of aortic arch and carotid sinuses

Question 14

what is information in the peripheral chemoreceptors sent via to get to the brainstem?

Answer 14

via the glossopharyngeal and vagus nerves to the nucleus in the brainstem called NTS

Question 15

what is the NTS?

Answer 15

nucleus tractus sollitarius

Question 16

what do peripheral chemoreceptors respond to

Answer 16

decreases in PO2 (hyoxia)

Question 17

describe the mechanism of the peripheral chemoreceptors

Answer 17

reduction in arterial PO2 - peripheral chemoreceptors stimulated - neural signals sent from carotid and aortic bodies to the NTS in brainstem - ventilation increases to restore PO2 levels

Question 18

at what level of arterial PO2 does progressive hyperventilation begin?

Answer 18

below 60mmHg

Question 19

where does the hypoxic response originate?

Answer 19

in carotic and aortic bodies

Question 20

what are central chemoreceptors?

Answer 20

clusters of neurons in the brainstem that are activated when PO2 is increased (hypercapnia) or pH decreased

Question 21

describe the mechanism of central chemoreceptors

Answer 21

increase in arterial PCO2 - central chemoreceptors stimulated - signals processed and information passed on to neuronal clusters in brainstem involved in generating breathing - ventilation increases to restore PCO2 levels

Question 22

where does the hypercapnic response originate?

Answer 22

in central chemoreceptors in brainstem

Question 23

what are mechanoreceptors?

Answer 23

sensory receptors that detect changes in pressure, movement and touch

Question 24

what do the mechanoreceptors detect in the respiratory system?

Answer 24

movement of lung and chest wall

Question 25

what do mechanoreceptors detect during inspiration?

Answer 25

inflation of lungs and movement of chest

Question 26

what is the role of the mechanoreceptors during inspiration?

Answer 26

pulmonary stretch receptors, can terminate inspiratory effort/prevent over inflation, adjust ventilation for changes in posture

Question 27

describe the mechanism of mechanoreceptors

Answer 27

inflation of lungs activates mechanreceptors - neural signals sent via vagus nerve to NTS in brainstem - ventilation adjusted accordingly

Question 28

what type of receptor is essential in adapting and adjusting breathing?

Answer 28

mechanoreceptors

Question 29

what is the receptor location of mechanoreceptors?

Answer 29

airway smooth muscle or airway epithelium

Question 30

what is the stimulus of mechanoreceptors in the smooth muscle?

Answer 30

inflation/distension of airway

Question 31

what is the reflex of mechanoreceptors in the smooth muscle?

Answer 31

termination of inspiration

Question 32

what is the stimulus of mechanoreceptors in the epithelium?

Answer 32

rapid lung inflation or deflation

Question 33

what is the reflex of mechanoreceptors in the epithelium?

Answer 33

sigh

Question 34

describe the integration of information in the brainstem

Answer 34

NTS receives information from mechanoreceptors and peripheral chemoreceptors- information processed in brainstem by respiratory neurons - cluster of respiratory neurons in brainstem generate rhythm of breathing (CPG) - rhythmic signal is sent to the respiratory muscles

Question 35

when are the inspiratory neurons active?

Answer 35

during inspiration

Question 36

when are the expiratory neurons active?

Answer 36

during expiration

Question 37

what are respiratory rhythm generating neurons in the brainstem

Answer 37

bilateral cluster of neurons with rhythm generating properties

Question 38

what are the two types of respiratory pattern generating neurons?

Answer 38

inspiratory and expiratory

Question 39

describe the output from brainstem to respiratory muscles

Answer 39

brainstem neurons produce rhythmic output - rhythmic neural signals sent to spinal cord - phrenic nerve exits spinal cord at cervical spinal cord level 3-5 - phrenic nerve innervates diaphragm - nerves exiting thoracic spinal cord innervate intercostal muscles

Question 40

what are the different respiratory groups in the brainstem?

Answer 40

pontine, ventral and dorsal

Question 41

where does the dorsal respiratory group of the brainstem sit?

Answer 41

in around the NTS

Question 42

what is the dorsal respiratory group composed of?

Answer 42

inspiratory neurons

Question 43

what is the function of the dorsal respiratory group?

Answer 43

integration of sensory information from the respiratory system (from chemoreceptors and mechanoreceptors via CNXI and CNX)

Question 44

what does the ventral respiratory group contain?

Answer 44

inspiratory and expiratory neurons, motor neurons (unlike DRG), contains regions which may be respiratory CPG

Question 45

what is the function of the pontine respiratory group?

Answer 45

modulates respiratory output

Question 46

what voluntary actions alter air flow?

Answer 46

breath holding, speaking and singing

Question 47

where do the voluntary breathing actions originate from

Answer 47

the motor cortex in the cerebral cortex

Question 48

what can be said about the control of voluntary breathing actions?

Answer 48

it is precise but not absolute as breath holding is overridden by ventilatory drive from chemoreceptors

Question 49

what are the 2 main mechanisms of motor control?

Answer 49

cortical neurons send axons to the brainstem and cortical premotor neurons send axons to motor neurons which control the muscles of respiration

Question 50

what do respiratory neurons in the brain do?

Answer 50

send neural signals to respiratory muscles to produce rhythmic breathing