Pulmonary Ventilation

Question 1

Muscles involved in Inspiration (and also Forced)

Answer 1

• Diaphragm- creates negative pressure in lungs

- (Diaphragm + External intercostal muscles + SCM and Scalenes)

Question 2

Muscles involved in Expiration (and also Forced)

• passive process

Answer 2

• Relaxtion of the Diaphragm which causes it to flatten out- increases pressure in lungs
• (Abdominal muscles such as Abdominus Rectus)

Question 3

Boyle’s Law

Answer 3

• Pressure is inversely proportional to volume

- Air moves from higher pressure to lower pressure

Question 4

Intrapulmonary pressure

Answer 4

Pressure in the lungs

Question 5

Atmospheric pressure

Answer 5

Pressure outside the lungs

Question 6

Intrapleural pressure

Answer 6

• Pressure in the space between the visceral and parietal pleura.
• Arrises due to surface tension in pleural fluid in the layers
• This pressure creates a suction
• Inspiration: chest wall recoils outwards and parietal pleura is pulled out

Question 7

If the intrapleural pressure is less than or equal to atmospheric pressure

Answer 7

Lung will collapse

Question 8

Physical properties of the lung

Answer 8

• Compliance- can expand up to a certain limit
• Elasticity- Ability of the ling to move back to its original shape
• Surface tension- alveoli are lined by a thin layer of fluid which exerts a force inwards which prevents them from collapsing

Question 9

Mechanoreceptors/ Stretch receptors

Answer 9

Where? - present on alveolar/bronchial walls and visceral pleura

• Prevents over-expansion of the lungs
• When activation they send signals (vagus) to respiratory centre to inhibit inspiration
  Hering-Breuer reflex

Question 10

Peripheral Chemoreceptors

Answer 10

Where? - Found in aortic arch and carotid bodies

• Sensitive to ph, pCO2, pO2 of arterial blood (mainly O2)
• When stimulated, signals are sent via vagus and glossopharyngeal nerves to respiratory centre in medulla

Question 11

Central Chemoreceptors

Answer 11

Where? - found in the ventral-lateral medulla

• Detect CO2 increase by CSF and monitoring H+

Question 12

NOTE on CO2

Answer 12

• Small increase or decrease in CO2 will greatly affect breathing patterns and rhythms

Question 13

Pneumotaxic center of Pons

Answer 13

• Fine tuning and decreases inhalation (inhibits Apneustic centre and DRG)

Question 14

Apneustic Centre

Answer 14

• Causes inhalation and signals DRG and inhibits Pnemotaxic Centre

Question 15

Dorsal respiratory group

Answer 15

• receives signals from receptors

- Has control over diaphragm and active normal inspiration

Question 16

Ventral respiratory group

Answer 16

• Forced inspiration and forced expiration

Question 17

Buffering when there’s too much CO2 (Hamburger effect)

Answer 17

• Bicarbonate ions from blood are swapped with Chloride ions from RBC cytosol
• Allows formation of CO2 and take excess protons away

Question 18

Buffering when there’s too much O2 (Haldane effect)

Answer 18

• Increase in pO2 forces CO2 to be released from Hb at the lungs
• More H+ binds to HCO3- in order to recreate stored Co2

Question 19

Bohr Effect

Answer 19

• More protons at tissues due to increase in CO2

- Protons decrease Hb’s affinity to oxygen so cause it to be released.

Question 20

Role of kidneys in O2/pH balance

Answer 20

• Produce erythropoietin whihc increases no. of Rbc
• H+ and HCO3- are selectively excreted in the urine
• Increase in CO2, more bicarbonate is retained.