Respiratory Systems 7 - Control of Breathing (Awake)

Question 1

List the functions of the respiraotyr muscles

Answer 1

• Maintenance of arterial PO2, PCO2, pH
• Defence of the airways
• Exercise
• Speech
• Sing
• Laugh, cry, express emotions
• Control of intrathroacic and intra-abdominal muscles (defecation, belch, vomiting)

Question 2

What is Ttot?

Answer 2

Time for one breath

Question 3

What is VE?

Answer 3

Minute ventillation

Question 4

How does tidal breath change in bronchitis and emphysema?

Answer 4

• Both have a lower Ttot, and a lower tidal volume

- Chronic bronchitis shows the greatest reduction

Question 5

What are the two controllers in the brain for breathing when awake?

Answer 5

• Automatic bulbopontine controller (brain stem)

- Behavioural suprapontine control (cerebral cortex)

Question 6

What is the function of the centres in the brain that control breathing?

Answer 6

• Involuntary centre is in the medulla, also called the metabolic centre
• Voluntary centre in the motor area of the cerebral cortex (allows breath holding)
• Metabolic will override behavioural
• Emotional responses can also influence the metabolic centre
• Metabolic centre responds to changes in pH of the blood, and PO2

Question 7

What is the peripheral chemoreceptor for arterial blood?

Answer 7

• Carotid body
• Lies in the junction of the internal and external carotid arteries in the neck
• Rapidly detects changes in PCO2 and PO2

Question 8

Which part of the medulla generates the respiratory rhythm?

Answer 8

The pre-Botzinger complex, also called the gasping centre

Question 9

Where are the receptors involved in reflex control?

Answer 9

• 5th nerve (nose and face)
• 9th nerve (pharynx and larynx)
• 10th nerve (bronchi and bronchioles

Question 10

What is the Hering-Breur reflex?

Answer 10

Senses lengthening and shortening of stretch receptors and terminates inspiration and expiration

Question 11

What are the two partsof the metabolic centre?

Answer 11

• Central part in the medulla responds to H+ in the ECF
• Peripheral part at the carotid bifurcation, the H+ receptors of the carotid body
• Fast responses in the carotid body, slow responses in the medulla

Question 12

What is controlled by control of ventillation?

Answer 12

• There seems to be little response to PaO2, but a large response to SaO2 (oxygen saturation)
• Falls in PaO2 increase sensitivity of the carotid body to PaCO2

Question 13

List some central causes of hypoventilation.

Answer 13

• Metabolic centre poisoning (acute)
• Disease of metabolic centre
• Congenital central hypoventilation syndrome
• Chronic mountain sickness

Question 14

List some peripheral causes of hypoventilation

Answer 14

• Muscle relaxant drugs, myasthenia gravis

- Neuromuscular with respiratory muscle weakness

Question 15

What causes dyspnea at rest and when exercising?

Answer 15

• At rest there is difficulty with inspiration or expiration

- Upon exercise there is excessive breathing for the task

Question 16

List the three types of breathlessness.

Answer 16

• Tightness (difficulty breathing due to airway narrowing)
• Air hunger (powerful urge to breathe)
• Increased work or effort (hyperventilation or increased resistance)

Question 17

What causes air hunger?

Answer 17

A mismatch between the minute ventilation demanded and the minute ventilation achieved

Question 18

What does breath holding time test for?

Answer 18

• The strength of behavioural vs metabolic controller
• Break point is prolonged by increasing lung volume, lowering PaCO2 or taking a breath near break point
• An expression of air hunger

Question 19

How is minute ventillation determined?

Answer 19

By the metabolic controller programming the mean inspiratory flow rate and inspiratory and expiratory times separately.

Question 20

How can central and peripheral conditions be distinguished?

Answer 20

• Central (cant breathe)
• Peripheral (wont breathe)
• Distinguished by measurement of respiratory muscle activation during CO2 stimulation

Question 21

How is intensity of breathlessness measured?

Answer 21

On a visual analogue scale during exercise or stimulation with CO2