Control of Ventilation

Question 1

why do we need O2 and why do we need to remove CO2

Answer 1

O2 - requirement for generating ATP through oxidative phosphorylation
CO2 - by product of respiration - helps produce bicarbonate buffer

Question 2

what is the equation for minute ventilation

Answer 2

Ve = breathing frequency (f) x tidal volume (VT)

5 L/min = 10 breaths per min x 500ml per breath

Question 3

why is the actual minute ventilation 3.5L/min at rest

Answer 3

due to dead space as reduces ml per breath from 500 to 350

Question 4

amount of breathing varies due to what

Answer 4

activity vs rest
altitude
disease

Question 5

how does do exercise affect breathing rate

Answer 5

O2 consumption ca increased 10 fold

Question 6

how does altitude affect breathing rate

Answer 6

less O2 in the air so need to work harder to maintain O2 supply

Question 7

why are smokers better suited for high altitude

Answer 7

bodies already adapted to hypoxic state

Question 8

how / what diseases affect amount of breathing

Answer 8

pulmonary and cardiovascular diseases which compromise gas exchange or delivery
sleep apnoea
opioid depression
chronic hypercapnia

Question 9

what are the three main classes of receptors for respiratory centres

Answer 9

lung
chemo
other

Question 10

what are the types of lung receptors

Answer 10

pulmonary stretch receptors
cough or irritant receptors
J receptors

Question 11

what are the type of chemoreceptors for respiration

Answer 11

central - ventral surface of medulla

peripheral - carotid bodies and aortic arch

Question 12

what are some other respiration receptors

Answer 12

nasal and upper airway
muscle stretch receptors
joint proprioceptors
arterial baroreceptors

Question 13

what are the respiratory centres that control automatic breathing

Answer 13

medulla: inspiratory and expiratory areas
pons: apneustic and pneumotaxic areas
cortical control of voluntary breathing can override respiratory centre control

Question 14

which are the targeted efferents for breathing

Answer 14

diaphragm - phrenic 345
intercostal muscles
abdominal muscles
accessory muscles in neck and shoulder

Question 15

where are the two respiratory centres in the brain

Answer 15

medulla - primary centre

pons - regulates medulla

Question 16

what is the pathway from the pons to the medulla and to output respiratory muscles

Answer 16

Pontine respiratory group - pneumotaxic centres triggers the apneustic centre
both these areas target the DRG
the DRG then stimulates both the VRG (mainly expiration) and respiratory muscles

Question 17

what is the nerve signalling in quiet breathing at rest

Answer 17

inspiratory nerve centre - DRG and some from VRG fire phasicly
but there is no expiratory nerve activity

Question 18

what is the process that occurs between the VRG and the DRG

Answer 18

reciprocal inhibition

Question 19

what can cause inhibition of inspiratory activity

Answer 19

therapeutic drugs = opiates, barbiturates
hypoxia
inhibition of blood supply

Question 20

what factors or sensors provide information to the respiratory sensors

Answer 20

pain/emotional stimuli in the brain 
higher brain cortical voluntary control 
stretch receptors in the lungs
irritant receptors in the lungs 
peripheral chemoreceptors in the carotid artery and aorta 
receptors in muscles and joints 
central receptors in the midbrain

Question 21

what higher brain centres influences breathing

Answer 21

cortical:
voluntary hyperventilation - hypocapnia alkalosis
voluntary breathing holding - hypoxia - unsustainable
hypothalamic:
emotions - anxiety / pain
sensory reflexes - pain/cold

Question 22

how do pulmonary stretch receptors affect breathing

Answer 22

afferent fibres from smooth muscle of bronchi and trachea
run in the vagus nerve to the respiratory centre in the medulla
inspiration inhibits the DRG and activates the VRG
(stop over inflation of the lungs)

Question 23

how do irritant / cough receptors affect breathing

Answer 23

receptors in airways that initiate expiration through cough
afferent fibres run in the vagus to reparatory centre
also found in nose and upper airways
local anaesthetics prevent these being triggered when a tube passes down

Question 24

how do muscle / joint receptors and proprioceptors affect breathing

Answer 24

muscle spindles rich in intercostals - few in diaphragm

activated by stretch associated with contraction of breathing - induced motion which can influence ventilation

Question 25

what are baroreceptors in affecting breathing

Answer 25

sense blood pressure can influence ventilation

increase blood pressure = decrease in ventilation

Question 26

what do J-receptors do

Answer 26

juxtacapillary

close to capillaries around alveolar wall - activated by traumas such as pulmonary oedema - this triggers ventilation

Question 27

how do central chemoreceptors affect breathing

Answer 27

specialised region close to medulla respiratory centres but also close to rice blood supply
sensitive to CO@ and H+
H+ cannot cross the blood brain barrier but CO2 can which informs levels of H+
rise in CO2 stimulates receptors in the medulla from the CSF and increases ventilation

Question 28

what are carotid and aortic bodies sensitive to

Answer 28

hypoxia - low O2
hypercapnia - high CO2
acidosis - high H+

Question 29

what is the primary sensory of hypoxia

Answer 29

glomus cell attached to afferent nerve
hypoxia triggers Ca influx into glomus cell which trigger release of transmitters which innate action potential in afferent nerve
dopamine is one transmitter released bu the excitation is from ATP and ACh