Respiratory strand: Lecture 9 - Control of Ventilation

Question 1

Why do we need to breath?

Answer 1

• to take in O2: requirement for generating ATP through oxidative phosphorylation
• to remove CO2

Question 2

What is minute ventilation?

Answer 2

Ve= breathing frequency x tidal volume

Question 3

What are the parts of the respiratory system that participate in gas exchange?

Answer 3

Only respiratory bronchi and alveoli

Question 4

What happens to the air that isn’t used?

Answer 4

Contributes to “dead space” of upper airways

Question 5

What factors cause breathing rate to vary?

Answer 5

1. Activity vs rest
2. Altitude - less O2 in air so need to work harder to maintain supply
3. Disease

Question 6

What diseases effect the amount of breathing?

Answer 6

• pulmonary diseases e.g emphysema
• cardiovascular diseases
• sleep apnoea: periodic cessation during sleep
• opioid depression of breathing
• conditions of chronic hypercapnia (abnormally high CO2 levels)- require oxygen sensing

Question 7

Which 3 factors effect breathing?

Answer 7

Input, output and control

flow chart slide 4

Question 8

What is in the respiratory centre?

Answer 8

Medulla and pons

image slide 5

Question 9

What does input involve?

Answer 9

Receptors sending information to the respiratory centre e.g chemoreceptors detecting CO2, lung receptors, nasal and upper airway receptors etc

Question 10

What does output involve?

Answer 10

Sending impulses from the respiratory centre to target muscles (effectors) controlling ventilation
effectors include diaphragm, intercostal muscles, abdominal muscles and accessory muscles

Question 11

What do the medulla and pons do?

Answer 11

Medulla is the primary centre for respiration as it contains the dorsal respiratory group (DRG) which is all too need to breath

Pons regulates medulla

Question 12

What is the ventral respiratory group (VRG) mostly responsible for?

Answer 12

Expiration

Question 13

What is inside pons?

Answer 13

• pneuomotaxic centre (simulates inspiration)

- apneustic centre (opposite to apneustic - inhibits inspiration)

Question 14

What occurs in the VRG (ventral respiratory group?)

Answer 14

Contains mixed neurones
some fire during inspiration,
some during expiration

Question 15

What happens in the DRG? (dorsal respiratory group)

Answer 15

Contains neurones

which fire during inspiration

Question 16

How is our reciprocal breathing pattern achieved?

Answer 16

DRG inhibits VRG

VRG inhibits DRG

Question 17

How can inspiratory activity be depressed?

Answer 17

• hypoxia
• a wide variety of therapeutic drugs e.g opiates, barbiturates and anaesthetic agents
• inhibition of blood supply

Question 18

What is hypocapnia?

Answer 18

Low CO2 - alkalosis

Question 19

What might influence the higher brain centre?

Answer 19

voluntary hyperventilation, voluntary breath holding, emotions (anger, anxiety), sensory receptors (pain, cold)

Question 20

What are pulmonary stretch receptors?

Answer 20

• mechanoreceptors
• afferent fibres from smooth muscle of bronchi and trachea
• run in vagus nerve to the respiratory centre (medulla)
• cause inspiration

Question 21

What is the hering-breuer lung inflation reflex?

Answer 21

limits minute ventilation (breathing frequency x tidal volume)
prevents over inflation of lungs

Question 22

What are irritant/ cough receptors?

Answer 22

• Receptors throughout the airways initiate an explosive expiration (a cough) when stimulated
• fibres from these receptors run in the vagus to the respiratory centre

Question 23

What do local anaesthetics do to irritant/cough receptor reflexes?

Answer 23

Prevent them when passing tubes into patients

Question 24

Which receptors relay information about activity induced motion which can influence ventilation?

Answer 24

Muscle/joint stretch receptors and proprioreceptors

Question 25

Give two other receptors that can influence ventilation?

Answer 25

• Baroreceptors (which sense blood pressure)
• J-receptors (lie close to capillaries around the alveolar walls - activated by traumas, inflammatory agents, pneumonia)

Question 26

Where are central chemoreceptors? What are they sensitive too?

Answer 26

• Specialised regions close to medulla respiratory centres

- sensitive to CO2 and H+

Question 27

Which out of CO2 and H+ can cross the blood brain barrier?

Answer 27

• H+ cannot cross the blood-brain barrier

- CO2 can, which informs about H+ levels

Question 28

What are the 4 neural regulators of breathing?

Answer 28

1. Pain receptors/ emotional stimuli acting through the hypothalamus
2. Stretch receptors in lungs
3. Cough/irritant receptors
4. Receptors in muscles and joints

Question 29

What is the chemical regulator of breathing?

Answer 29

Chemoreceptors

Question 30

What does a glomus body do?

Answer 30

Primary sensor of hypoxia

-causes signal transduction in afferent nerve into the brain