4.6 Homeostatic Control of Respiration Flashcards
Can we consciously influence both parts of respiration?
No. Only ventilation. Gas exchange is entirely passive.
In terms of homeostatic regulation of respiration, what are three substances that are detected by peripheral chemoreceptors in arterial blood?
- Partial pressure of CO2
- Partial pressure of O2
- pH
What is CN X?
Vagus nerve
What is CN IX?
Glossopharyngeal
Where in the brainstem to central and peripheral chemoreceptors deliver information?
Central pattern generator (CPG)
Where does the CPG send information? Why?
The spinal cord, because it innervates skeletal muscles
What is the most vascularised organ in the body?
Carotid body
What are the two types of peripheral chemoreceptors?
- Aortic body
- Carotid body
Describe the basic mechanism of a peripheral chemoreceptor
- Highly vascularised -> can measure blood
- Glomus cells (type 1 and type 2) can measure levels of chemicals
- Information is sent via afferent nerves to the brain
What is hypercapnia?
Increase in the partial pressure of CO2
What can PCRs detect?
- Hypercapnia
- Hpoxia
- Acidosis
Describe the shape of the graphical relationship between CO2 partial pressure and alveolar ventilation
Linear
Describe how acidosis or hypercapnia can lead to generation of an action potential in glomus cells.
- Inhibition of K+ channels (cannot leave cell) due to influx in H+ or breakdown of newly-generated carbonic acid
- Cell becomes depolarised, leading to Ca2+ influx
- Ca2+ influx causes neurotransmitter release and vesicular activity
Describe how hypoxia can lead to generation of an action potential in glomus cells.
Nobody really knows, but it’s a similar mechanism to hypercapnia and acidosis
Which type of chemoreceptors are the dominant driver of increased ventilation in response to hypercapnia?
Central chemoreceptors
