PPoS: ventilation

Question 1

effect of sectioning below pons and medulla

Answer 1

apnoea: falt line

Question 2

effect of sectioning above pons

Answer 2

eupnoea: normal breathing = central pattern generator

Question 3

effect of sectioning between pons and medulla

Answer 3

gasping. short inspiration, long inspiration

Question 4

effet of sectioning mid-pons, middle of 4th ventricle

Answer 4

apeneusis: long inspiration, short expiration

Question 5

what is the pneumotaxic centre, where is it and what are the effects of disconnecting it

Answer 5

inhibits inspiratory phase

upper pons. disconnected leads to more time spent inspiring

Question 6

what are the 4 main respiratory nuclei in medulla

Answer 6

dorsal respiratory group, ventral respiratory group, pre-botzinger complex and botzinger complex

Question 7

what is the significance of PBC

Answer 7

key centre for respiratory rhythmogenesis

pscemaker

Question 8

where are PBC and BC located

Answer 8

near nucleus retrofacialis (RTN)

Question 9

where does DRG receive inputs from

Answer 9

from chemoreceptors and lung mechanoreceptors (relayed by IX and X cranial nerves and spinal cord)

Question 10

what do DRG inspiratory neurones do

Answer 10

• inhibit expiratory neurones in VRG and pontine respiratory group (PRG) = pattern
• neural activity to phrenic nerves
• control depth and rate of breathing
• receptor info: override control

Question 11

what does the cortex do

Answer 11

higher centre:
control ventilation
interrupts breathing pattern generated

Question 12

what is the apneustic centre and what does it do

Answer 12

prolongs inspiration

absebce = gasping

Question 13

where is DRG located

Answer 13

nucleus tractus solitarius NTS

Question 14

what does the DRG do

Answer 14

• control insp
• fire along phrenic nerves to diaphragm: depth and rate of breathing
• insp neurones inhibit exp neurones in VRG and pontine rep group (PRG)

Question 15

where does DRG receive inputs from

Answer 15

• chemoreceptors and lung mechanoreceptors (relayed by IX and X cranial nerves and spinal cord)
• higher brain centres - override

Question 16

what does the VRG contain

Answer 16

nucleus ambiguosis NA

nucleus retroambiguosis RTN

Question 17

site of juxtapulmonary receptors

Answer 17

alveolar, bronchial walls.

close to capillarues

Question 18

what do J receptors cause

Answer 18

• aponea or rapid shallow breathing
• fall in HR and BP
• laryngeal constriction
• relax skeletal muscles

Question 19

what are J receptors stimulated by

Answer 19

• increased alveolar wall fluid
• oedema
• pulmonary congestion
• microembolisms
• inflammatory mediators e.g. histamine

Question 20

what reflexes do stretch receptors stimulate

Answer 20

• hering-breur inflation reflex: inflation inhibits inspiration
• deflation reflex: deflation augments inspiration

Question 21

where are stretch receptors located and what do they do

Answer 21

• smooth bronchial wall muscle
• makes insp shorter and shallower
• delay next insp cycle

Question 22

action of irritant receptors

Answer 22

Receptors in trachea lead to cough
those in lower airways hyperpnoea
Also reflex bronchial and laryngeal constriction

Responsible for deep augmented breaths seen every 5-20 mins at rest

Question 23

location of irritant receptors

Answer 23

through airway between epithelial cells

Question 24

stimulation of irritant receptors

Answer 24

Irritant gases, smoke and dust, inflammation, rapid large inflations and deflations, pulmonary congestion

Question 25

site and stimulation of prorioceotive receptors

Answer 25

-resp muscles
-Stimulated by: shortening and load of
respiratory muscles (but not diaphragm)
- Important for coping with increased load, and achieving optimal tidal volume and frequency.

Question 26

pain receptors

Answer 26

brief apnoea followed by increased breathing

Question 27

receptors in trigemina region and larynx

Answer 27

apnoea or spasm, heart rate

nasal trigeminal nerve endings – sneeze reflex

Question 28

arterial baroreceptors

Answer 28

stimulation inhibits breathing

Question 29

whats the ventilatory response to CO2

equation of PACO2

Answer 29

negative feedback control mechanism
if alveolar vent halves, PACO2 doubles
PACO2 inversely proportional to rate of CO produced/alveolar vent

Question 30

describe the combination hypoxia and hypercapnia

Answer 30

synergistic

combined effect is greater than sum of ind effects

Question 31

where are chemoreceptors located

Answer 31

ventrolateral surface of medulla

near exit of C IX and X

Question 32

describe what central chemoreceptors respond to

Answer 32

pCO2 from blood, [HCO3-] from CSF

Question 33

equation for [H] at chemoreceptor

Answer 33

proportional to PCO2 / [HCO3-]

Question 34

what is an adaptation of central chemoreceptors to prolonged hypercapnia

Answer 34

• CSF pH is normal (but arterial pCO2 is high)
• ventilatory drive decreases (inappropriate)
  e. g. chronic resp disease

not relying on hypercapnic drive to breath, rely on hypoxic drive = DO NOT GIVE PATIENT O2

Question 35

what is an adaptation of central chemoreceptors to altitude

Answer 35

• CSF initially alkaline due to hypoxic drive

- CSF pH will return to normal and drive decreases

Question 36

where are peripheral chemoreceptors located and their innervations

Answer 36

aortic bodies - vagus nerve

carotid body - carotid sinus nerve (a branch of glossopharyngeal nerve)

Question 37

what are the two main types of carotid bodies

Answer 37

• type 1 - gloms cells: many neurotransmitters, content axons which innervate them (carotid sinus nerve fibres)
• type 1 - sheath cells: enclose type 1 cells

Question 38

function of peripheral chemoreceptors

Answer 38

-increase pCO2 and H increases ventilation
-decrease pO2 increases vent
(respond to hypercapnia, hypoxaemia and metabolic acidosis)
-v fast response - to oscillations in blood