7- Breathlessness And Control Of Breathing

Question 1

How do you calculate minute ventilation

Answer 1

Tidal volume x60. /Duration of a single respiratory cycle

Question 2

What is the carotid body

Answer 2

It lies at the junction of the internal and external carotid arteries in the neck
•It is a rapid response system for detecting changes in arterial PCO2 and PO2

Question 3

Where does central control of breathing come from

Answer 3

group pacemaker” activity coming from about 10 groups of neurons in the medulla near nuclei of IX and X cranial nerves

Question 4

Describe reflex control of breathing

Answer 4

Vth nerve: afferents from nose and face (irritant)
•IXth nerve: from pharynx and larynx (irritant)
•Xth nerve: from bronchi and bronchioles (irritant and stretch)

Question 5

What are some causes of metabolic acidosis

Answer 5

diabetic ketoacidosis, salicylate overdose, renal tubular defects

Question 6

What are some causes of metabolic alkalosis

Answer 6

vomiting, diuretics, dehydration

Question 7

What 3 factors make up Dyspnoea

Answer 7

Tightness: difficulty in expanding the thorax, generally associated with airway narrowing
Increased work and effort, either the hyperventilation of exercise, or breathing against increased external resistance or at high end–expired volume.
Air hunger describes a powerful urge to breathe such as at the end of a prolonged breath hold.

Question 8

How is breathing with a nose clip different to normal

Answer 8

your breathing becomes deeper and hence VT increases
• Using a nose clip also means that breathing becomes slower (decrease in
frequency) but ventilation remains around the same

Question 9

How is breathing with COPD different to normal

Answer 9

people with COPD breathe much shallower and faster

They have difficulty expiring

Question 10

How does the CNS control breathing

Answer 10

Involuntary or metabolic centre = MEDULLA (bulbo-pontine brain)
• Voluntary or behavioural centre = motor area of CEREBRAL CORTEX
• Metabolic will always override behavioural

Question 11

What are the 2 metabolic controllers in breathing

Answer 11

Central part in the medulla responding to the hydrogen ion concentration in the extracellular fluid
Peripheral part at the carotid bifurcation (carotid sinus) - there are hydrogen ion receptors here as well