Control of Ventilation

Question 1

what controls breathing

Answer 1

brainstem

Question 2

what two groups of nuclei in the brainstem control breathing

Answer 2

1. medullary group (rhythmicity centre)
2. pontine group (apneustic, pneumotaxic)

Question 3

what is the input of breathing into the brainstem

Answer 3

vagus and glossopharyngeal nerve

Question 4

what does the dorsal and ventral resp groups control

Answer 4

dorsal resp group: insipratory

ventral resp group: inspiratory/expiratory

Question 5

what is the function of dorsal resp group neurons

Answer 5

inspiratory neurons that discharge during inspiration and stop discharging during expiration

Question 6

how do DRG initiate inspiration

Answer 6

with a weak burst of action potentials which gradually increase then stop (RAMP signal) –> breathing pacemaker

Question 7

what do the DRG signals innervate

Answer 7

phrenic nerve supply of the diaphragm

Question 8

how does DRG communicate with ventral resp grou

Answer 8

relays to VRG which stimulates muscles of expiration (intercostals, abdominal muscles) during heavy exercise

Question 9

what neurons do VRG contain

Answer 9

both inspiratory and expiratory neurons

Question 10

what is the function of VRG

Answer 10

drive neurons innervating intercostal or abdominal muscles (heavy exercise)

inactive during normal quiet respiration

Question 11

what is the function of apneustic centre

Answer 11

sends stimulatory stimuli to inspiratory neurones

Question 12

what is the function of nucleus of the solitary tract (NST)

Answer 12

essential for processing and coordination of resp and sympathetic responses to hypoxia

first synaptic station of cardiorespiratory afferent inputs (including peripheral chemoreceptors, baroreceptors and pulmonary stretch receptors)

Question 13

what is the function of pneumotaxic centre

Answer 13

control cessation of inspiratory ramp signal from DIG

Question 14

what is hypoactivation of pontine resp centres

Answer 14

prolonged deep inspiration

Question 15

what is hyperactivation of pontine resp centres

Answer 15

shallow inspiration

Question 16

what is the function of the pre-botzinger complex

Answer 16

houses pacemaker neurons

responsible for resp rhythm generation –> central pattern generator (CPG)

Question 17

identify the structures in the brainstem

Answer 17

Question 18

what are the neurotransmitters that the NTS respond to

Answer 18

receiving the excitatory drive involes glutamate, ATP and acetylcholine

Question 19

what are the functions of central chemoreceptors

Answer 19

respond to increase in arterial PCO2

signals processed and information passed on to neuronal clusters in brainstem involved in generating breathing

ventilation increases to restore PCO2 levels

Question 20

where are central chemoreceptors located

Answer 20

in brainstem

Question 21

how do changes in PCO2 have changes on ventilation

Answer 21

hypercapnic response increases ventilation

plays major role in moment to moment control of breathing

Question 22

how do central chemoreceptors respond to increase CO2 (hypercapnia)

Answer 22

through increases in H+ concentration

CO2 + H2O <–> H2CO3 <—> HCO3- + H+ <—> H+ + CO3^2-

decreases the pH –> activates central chemoreceptors to stimulate ventilation

Question 23

where is the location of the central chemoreceptors

Answer 23

unclear

the retrotrapezoid nucleus (RTN) may be most critical

it sends signals to central pattern generator (CPG) in medulla

Question 24

what are peripheral chemoreceptors

Answer 24

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

Question 25

how do peripheral chemoreceptors send their info

Answer 25

glossopharyngeal nerve

vagus nerve

Question 26

where do peripheral chemoreceptors send their info to

Answer 26

nucleus tractus solitarius (NTS) in the brainstem

Question 27

what do peripheral chemoreceptors monitor

Answer 27

PO2, PCO2, [H+]

Question 28

what occurs when PO2 decreases

Answer 28

firing rate of peripheral chemoreceptors increases –> goes to the NTS in brainstem –> increases ventilation

Question 29

what do respiratory mechanoreceptors respond to

Answer 29

detect movement of lung and chest wall

are activated when lung inflates

Question 30

what occurs when resp mechanoreceptors are activated

Answer 30

neural signals sent via vagus nerve to NTS in brainstem –> ventilation adjusted

Question 31

summarize this

Answer 31

Question 32

what are the effects of altitude

Answer 32

acute hypoxemia causes hyperventilation by activation of peripheral chemoreceptors

increases PaO2 and decreases PaCO2

Question 33

what are the longer term adjustments to higher altitude (4)

Answer 33

1. production of more erythrocytes
2. decreased affinity of oxygen for Hb due to increase 2,3 - DPG (bohr shift to right)
3. increase in pulmonary surface area
4. increased capillary density in muscle

Question 34

what is brisket disease

Answer 34

high altitude pulmonary hypertension (HAPH)

chronic alveolar hypoxia –> leads to hypoxic vasoconstriction and remodelling of pulmonary circulation

leads to right-sided heart failure

edematous fluid accumulates in ventral portions of chest –> brisket

Question 35

what is the effect of exercise on ventilation

Answer 35

increase after onset is intially rapid but then steady state reached

PO2, PCO2, and pH remain relatively constant