West Chapter 8 - Control of ventilation Flashcards
Where does the normal automatic process of breathing originates?
From the brainstem
What are the 3 groups of neurons that are part of the respiratory centers? What is the global role of the respiratory centers?
- Medullary respiratory center
- Apneustic center
- Pneumotaxic center
Responsible for generating the rhythmic pattern of inspiration and expiration
What is the other part of the brain that can partially override the function of the brainstem?
Cortex
What is a crucial point for efficacy of the different groups of muscle respiration? What are the 4 different groups of muscles?
Coordination
diaphragm, intercostal muscles, abdominal muscles, accessory muscles
What are the 3 basic elements of the respiratory control system?
Central controller (brainstem: pons and medulla ; cortex; others)
Effectors (respiratory muscles)
Sensors (chemoreceptors)
To what changes are central chemoreceptors sensitive to? How does it impact ventilation?
- changes in H+ concentration in brain extracellular fluid (CSF mostly + local blood flow, local metabolism)
- increase in H+: stimulates ventilation, and vice-versa
Is the BBB permeable or impermeable to H+ and HCO3- ? To CO2 ?
Impermeable to H+/HCO3-
Permeable to CO2
What happens with thechemoreceptors and ventilation when blood pCO2 rises ?
CO2 diffuses into CSF
=> liberates H+, decreases pH
=> stimulates chemoR
=> stimulates ventilation
Changes in CSF pH for a given change in PCO2 is greater than in blood. Why is that?
Less proteins than in blood => lower buffering capacity
Are the central chemoreceptors sensitive to PO2 of blood?
No. Sensitive to pCO2.
Where are the peripheral chemoreceptors located?
At the bifurcation of the common carotid arteries, an on the aortic arch.
What changes do peripheral chemoreceptors sense?
- decrease in arterial pO2 and pH
- increase in arterial pCO2
What are the 4 types of receptors found in the lungs?
- Pulmonary stretch receptors: discharge in response to distension of the lung, causing increase in expiratory time
- Irritant receptors
- J receptors
- Bronchial C fibers
How much does blood pO2 normally affect ventilation? In which context does it become especially important? What are the receptors involved?
Normal condition: no effect
High altitude / some chronic lung diseases : ventilatory response to hypoxia becomes important
Only the peripheral chemoreceptors are involved
Does exercise affect ventilation? How much? How?
Yes, it causes a large increase in ventilation. The cause is poorly understood.
