Control of Ventilation Flashcards
What physical structures must be stimulated to cause inspiration?
Skeletal muscles (the diaphragm and external intercostals)
What innervates the thoracic-abdominal diaphragm?
The phrenic nerve
Which nerves innervate the external intercostal muscles?
The intercostal nerves
Where are the respiratory centres located?
In the pons and medulla of the brain
What can be said about the voluntary/involuntary nature of breathing?
It is mostly subconscious but can be subject to voluntary override
Severing of the spinal chord above the ventral rami of spinal nerves C3, 4 and 5 do what?
Kill you
C3, 4 and 5 keep your heart and lungs alive
The respiratory centres set an automatic rhythm of breathing by firing smooth and repetitive bursts of action potentials in which part of the respiratory centre?
The dorsal respiratory group
What four other aspects can modulate ventilation?
- Emotion (limbic system)
- Voluntary override
- Mechano-sensory input from thorax
- Chemical changes
What two types of chemoreceptor modulate ventilation?
Central and peripheral
What chemical route, central or peripheral, is the main control for ventilatory function?
Central
Central chemoreceptors response directly to what?
[H+] in cerebrospinal fluid
What does the [H+] indicate?
PCO2
Where are central chemoreceptors located?
Medulla of the brain
Where are peripheral chemoreceptors located in the body?
Carotid and aortic bodies
What do peripheral chemoreceptors detect?
Changes in arterial PO2 and [H+]
Changes in plasma pH will alter ventilation via what chemoreceptor pathway?
Peripheral
If plasma pH falls, ventilation will be ______
Stimulated (causing acidosis)
If plasma pH increases ventilation will be ______
Inhibited (alkalosis)
List common drugs which depress respiratory activity
Barbituates and opioids
What effect do most anaesthetic agents have on respiratory activity?
Increase respiration rate but decrease tidal volume so decrease alveolar ventilation
What effect does nitrous oxide have on the nervous system?
A common sedative/light anaesthetic - blunts peripheral chemoreceptor pathway to falling PO2
In what kind of patients would the use of nitrous oxide be contraindicated?
Problematic in lung disease cases
What is hypoxic drive?
A scenario seen in many lung disease cases where the body regulates its respiratory activity by monitoring PO2 not PCO2
What common treatment for lung diseases would aggravate a patient demonstrating hypoxic drive?
Administering oxygen
