Control of ventilation

Question 1

What happens to the PaCO2 when the CO2 stays the same but the ventilation halves?

Answer 1

PaCO2 will double

Question 2

What happens to PaCO2 when CO2 stays the same but ventilation doubles?

Answer 2

PaCO2 will halve.

Question 3

What is the purpose of ventilation?

Answer 3

To maintain blood gas and pH

Question 4

What are features of control of respiration?

Answer 4

Automatic, unconscious, negative feedback system (maintain blood gases and pH for optimum cellular function), override manually.

Question 5

What is Ondine’s curse?

Answer 5

Congenital central hypoventilation syndrome.

Question 6

WHat are the cortical influences that override control of respiration?

Answer 6

Coughing, sneezing, talking, laughing.

Question 7

What are the limbic influences that override control of respiration?

Answer 7

Fear, anxiety, anger and pain.

Question 8

what is the feedback control system?

Answer 8

Sensors (chemoreceptors) are the input to the central controller (pons, medulla) and produce an output to the effectors (resp muscles).

Question 9

What is the function of the central controller?

Answer 9

generates resp rhythm, controls rate and depth and pattern on respiration.

Question 10

What is the medullary centre?

Answer 10

Dorsal for inspiration, ventral for inspiration and expiration and dormant whilst quiet breathing.

Question 11

What is the apneustic area?

Answer 11

Lower pons, excitatory effect on inspiratory area of medulla
Causes prolonges inspiration

Question 12

What is the pneumotaxic area?

Answer 12

Controls transition of inspiration to expiration by inhibiting inspiration, regulate inspiratory volume and rate.

Question 13

What is the dorsal resp group?

Answer 13

Control of resp, generate rate and rhythm.
Located in dorsal medulla- close to sensory termination of vagal and glossopharyngeal nerves that transmit sensory signals to resp centre.

Question 14

What is the inspiratory ramp signal?

Answer 14

Nervous signal to inspiratory muscles that steadily increasing signal increases over 2 seconds. Results in inspiratory muscle contraction, air enters lungs. signal stops for 3 seconds and lungs passively recoil (expiration).

Question 15

What are the 4 nuclei in the ventral resp group?

Answer 15

-Botzinger complex
-pre- botzinger complex
-nucleus ambiguous
-nucleus retroambiguous

Question 16

Function of Botzinger complex?

Answer 16

Expiration

Question 17

Function of pre botzinger complex?

Answer 17

sets pace for respiration

Question 18

function of nucleus ambiguous?

Answer 18

inspiratory neurons

Question 19

function of nucleus retroambiguous?

Answer 19

inspiratory and expiratory neurons

Question 20

function og apneustic centre?

Answer 20

stimulates dorsal resp group, increases inspiration.
feedback from vagal nerves and other resp centres

Question 21

function of pneumotaxic centre?

Answer 21

signals to inspiratory area, controls switch off point for inspiratory ramp (controls filling phase of lung cycle)

Question 22

what happens to ramp time if strong signal from pneumotaxic?

Answer 22

reduces ramp time to 0.5 seconds, reduces duration of expiration (increases RR)

Question 23

what happens to ramp time if weak signal from pneumotaxic?

Answer 23

increases duration of inspiration and expiration (decreases RR)

Question 24

What are the types of resp receptors?

Answer 24

-chemoreceptors (central and peripheral)
-lung receptors (J, irritant, stretch)
-receptors in muscles and joints

Question 25

Where are central chemoreceptors?

Answer 25

Ventral surface of medulla in brain stem

Question 26

function of central chemoreceptors?

Answer 26

respond to H+ conc in CSF (high H+ then increase ventilation vice versa) responsible for 80% response to CO2

Question 27

what causes increase in H+ ions in CSF?

Answer 27

CO2 diffusing across blood brain barrier and therefore stimulate receptors

Question 28

where are peripheral chemoreceptors found?

Answer 28

-carotid bodies at bifurcations of common carotid arteries -aortic bodies above and below aortic arch

Question 29

what is the function of peripheral chemoreceptors?

Answer 29

respond to changes in PCO2, H+ and PO2. 20% response to CO2 (faster response)

Question 30

where are stretch receptors found?

Answer 30

smooth muscle of bronchial walls

Question 31

what is the function of stretch receptors?

Answer 31

-shortening inspiration -shallow inspiration -delay before next breath

Question 32

what is the Hering- Breuer reflex?

Answer 32

vol reflex- lung inflation inhibits inspiratory muscle activity, prevents overinflation of lung. when airways stretched, receptors stimulated and send impulses to dorsal resp group=> switches off insp ramp and stops insp resulting in expiration (reflex weak in normal breathing)

Question 33

what are J receptors?

Answer 33

-juxtaposition receptors or C fibre receptors. -stimulated by pulmonary oedema, micro embolisms, inflam mediators -lower HR, BP and constrict larynx

Question 34

where are J receptors?

Answer 34

on alveolar or bronchial walls (close to capillaries)

Question 35

where are irritant receptors?

Answer 35

located throughout airway in-between epithelial cells

Question 36

what is the function of irritant receptors?

Answer 36

stimulated by irritant gases, smoke, dust, airway deformation -bronchial and laryngeal constriction, sneezing and coughing -responsible for deep sighs taken every 5-20 mins during normal breathing

Question 37

where are proprioceptors?

Answer 37

in Golgi tendon organs, muscle spindles and joints

Question 38

what is the function of proprioceptors?

Answer 38

stimulated by increased load and shortening resp muscles (help achieve optimal VT and frequency)