Respiratory Systems 7 - Control of Breathing (Awake) Flashcards
List the functions of the respiraotyr muscles
- 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)
What is Ttot?
Time for one breath
What is VE?
Minute ventillation
How does tidal breath change in bronchitis and emphysema?
- Both have a lower Ttot, and a lower tidal volume
- Chronic bronchitis shows the greatest reduction
What are the two controllers in the brain for breathing when awake?
- Automatic bulbopontine controller (brain stem)
- Behavioural suprapontine control (cerebral cortex)
What is the function of the centres in the brain that control breathing?
- 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
What is the peripheral chemoreceptor for arterial blood?
- Carotid body
- Lies in the junction of the internal and external carotid arteries in the neck
- Rapidly detects changes in PCO2 and PO2
Which part of the medulla generates the respiratory rhythm?
The pre-Botzinger complex, also called the gasping centre
Where are the receptors involved in reflex control?
- 5th nerve (nose and face)
- 9th nerve (pharynx and larynx)
- 10th nerve (bronchi and bronchioles
What is the Hering-Breur reflex?
Senses lengthening and shortening of stretch receptors and terminates inspiration and expiration
What are the two partsof the metabolic centre?
- 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
What is controlled by control of ventillation?
- 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
List some central causes of hypoventilation.
- Metabolic centre poisoning (acute)
- Disease of metabolic centre
- Congenital central hypoventilation syndrome
- Chronic mountain sickness
List some peripheral causes of hypoventilation
- Muscle relaxant drugs, myasthenia gravis
- Neuromuscular with respiratory muscle weakness
What causes dyspnea at rest and when exercising?
- At rest there is difficulty with inspiration or expiration
- Upon exercise there is excessive breathing for the task
List the three types of breathlessness.
- Tightness (difficulty breathing due to airway narrowing)
- Air hunger (powerful urge to breathe)
- Increased work or effort (hyperventilation or increased resistance)
What causes air hunger?
A mismatch between the minute ventilation demanded and the minute ventilation achieved
What does breath holding time test for?
- 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
How is minute ventillation determined?
By the metabolic controller programming the mean inspiratory flow rate and inspiratory and expiratory times separately.
How can central and peripheral conditions be distinguished?
- Central (cant breathe)
- Peripheral (wont breathe)
- Distinguished by measurement of respiratory muscle activation during CO2 stimulation
How is intensity of breathlessness measured?
On a visual analogue scale during exercise or stimulation with CO2
