Respiratory control

Question 1

what two variables of breathing does the brain (thru phrenic nerve and medullary center) control?

Answer 1

frequency and tidal volume

(Vt) VE= f*Vt

determines timing (f)—> determines depth (VT)—-> to motorneurons

Question 2

is phrenic firing during inspiration or expiration?

Answer 2

inspiration

Question 3

what is the site in the medulla that tell lungs when to breath? (generating first part of timing/frequency of respiratory rhythm)?

Answer 3

pre-botzinger complex

*fires more at beginning of respiration

Question 4

what is the bart of medulla that controls length of inspiration (second part of timing/frequency of respiratory rhytm)?

Answer 4

PRG

Question 5

what happens when there is a lesion in the PRG?

Answer 5

lose ability to turn off inspiration without help from vagus nerve—> apneusis (stuck in inspration)

Question 6

what part of medulla sends sensory info to lungs to generate its breathing pattern (how fast/deep/etc)?

Answer 6

DRG (responsible for 95% of phrenic motor input)

Question 7

what part of medulla gives a smaller motor input to phrenic nerve and inspiratory muscles to control breathing pattern?

what part sends input to the upper airway and muscles of expiration?

Answer 7

rostral VRG

caudal VRG

Question 8

what is the appearance of inspiration in:

apenuesis?

of apnea?

Answer 8

apneuisis: maintained inspiration
apnea: no inspiration (absence of effort)

Question 9

what are the results of:

apneusis?

apnea?

Answer 9

apneusis: pontine damage
apnea: medulla or spinal cord damage

Question 10

what are the effects of:

apeursis?

apnea?

Answer 10

apneusis: slight delay, but then increase in CO2, decrease O2, death if not treated
apnea: increase in CO2, decrease O2, death if not supported

Question 11

what are chemoreceptors in respiratory system?

what do they respond to?

why are they so important?

Answer 11

neurons that increase firing rate in response to

• increse CO2
• increase O2
• increase H

these condtions normally decrease activity in respiratory neurons (decrease during hypoxia or hypercapnia)–> decrease ventilation and gas exchange–> exacerbates problem–>

chemoreceptors stop this from happening by activating respiratory centers and increasing respiration–> keeping us alive!!

Question 12

what is chemosensitvity?

Answer 12

ability of certain chemicals to change discharge rate of sensitive neurons

Question 13

what are the two set of respiratory chemoreceptors, where are they located, and what are they sensitve to?

Answer 13

1. central

• ventral surface of medulla
• directly to pH of CSF and indirectly to CO2 in blood/plasma

2. peripheral

• aortic arch and (more importantly) carotid body
• decrease in O2, increase in CO2, increase in H+

*carotid body also sensitive to dopamine

Question 14

how do the central chemoreceptors respond indirectly to CO2 in the blood?

Answer 14

CO2 crosses BBB–>

mixes with H2O—>

forms H2CO3 via carbonic anhydrase—>

rapidly breaks down to form H and CO3—>

H then stimulates chemoreceptors

**must happen this way because H+ cannot cross BBB

Question 15

what drives us to breathe?

Answer 15

stimulation of central chemoreceptors by H+

Question 16

how do peripheral chemoreceptors differ from central chemoreceptors?

Answer 16

• more sensitive to O2
• increased frequency of afferents from carotid body/aortic arch
• increased Vt
• quicker than central
• stimulated also by O2, CO2, pH BUT it is directly for both (plus it responds more to O2)

Question 18

what influence does peripheral chemoreceptors have?

Answer 18

acute changes in blood gases

Question 19

what conditions do central chemoreceptors respond to?

what are the effects of?

Answer 19

hypercapnia (slower than peripheral)

increase in respiratory rate, depth of breath

Question 20

what do peripheral chemoreceptors respond to?

what is there effect?

Answer 20

hypercapnia, hypoxia, acidosis

increase in respiratory rate and depth in breath

Question 21

where are slow-adapting pulmonary stretch receptors located?

sensitive to?

where do fibers travel?

what is their effect?

Answer 21

airways

stretch of airways (directly proportional to lung volume)

travel to brain in Vagus nerve

inhibit inspiration and prolong expiration

Question 22

what can bypass medullary centers and send input directly to muscels of respiration?

Answer 22

cortex!

help control breathing when holding your breath and talking

Question 23

who are the slow-adapting pulmonary stretch receptors important for controlling respiration in?

Answer 23

infants- because babies dont use lungs in utero (every breath)

adults who are exercising (so not every breath)

**not crucial in controlling Vt in adults at rest

Question 24

where are rapidly-adapting pulmonary stretch receptors located?

sensitive to?

fibers travel where?

their effect?

Answer 24

airways

irritation, foreign bodies in airways, stretch

to brain in vagus

cough

Question 25

where are the J (juxtacapillary) receptors located?

sensitive to?

fibers travel where?

effects?

Answer 25

near blood vessels of alveoli

pulmonary edema

to brain in vagus

cough, tachypnea

Question 26

what are the J receptors and the rapidly adapting pulmonary stretch receptors main roles?

Answer 26

protecting the gas exchange surfaces by overriding the normal respiratory control systems (obviously not with every breath)

very important for survival!