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Flashcards in Control of respiration Deck (13):
1

Describe the function of the main respiratory center in the brain (the medulla).

The medulla can generate a rhythm spontaneously, without input from the lungs or anywhere else in the body. Rhythm generator is the rostral ventrolateral medulla, and specifically an area called the preBotzinger complex. The breathing rhythm drives the respiratory motoneurons and interneurons in the spinal cord, which then drive the respiratory muscles, both inspiratory and expiratory.

2

Describe the locations and functions of peripheral chemoreceptors.

Divided into two groups, the carotid and aortic chemoreceptors. Both groups are stimulated by decreases in arterial PO2 or increases in PCO2

Carotid: located in the carotid bodies, which are small nodules of tissue found bilaterally at the bifurcation of the common carotid arteries into the internal and external carotids. Stimulated by decreases in arterial pH. Sense the level of O2.

Aortic: located in the aortic bodies, found around the arch of the aorta and between the arch of the aorta and the pulmonary artery.

3

Describe the location and functions of central chemoreceptors.

Situated close to the ventral surface of the medulla. They
bind to protons in the brain, but they are not sensitive to the level of protons in arterial blood, but instead arterial PCO2.

4

Understand the relative importance of peripheral or central chemoreceptors under different conditions

Carotid: Important during metabolic acid-base disturbances, as they are the sole detectors of arterial pH in the body that can mediate ventilatory changes.

Central: Since the CSF contains much less protein than blood, it has a much lower buffering capacity. As a result, the change in CSF pH for a given change in PCO2 is greater than in blood. The recovery of the CSF pH through the compensatory change in bicarbonate is of primary importance for the initial acclimatization to high altitude

5

Describe the role of the blood-brain barrier in determining the function of central chemoreceptors.

The blood-brain barrier membrane greatly restricts diffusion of ions such as H+ between blood and CSF, while it allows free diffusion of fat-soluble substances like CO2.

CO2 first crosses the blood-brain barrier into the CSF, where it combines with water and dissociates into protons and bicarbonate. The chemoreceptors then bind the protons and stimulate breathing (increase ventilation (VA ).

There are no central chemoreceptors for oxygen

6

Describe the integrated response to changes in altitude in terms of the control of respiration.

Exposure to high altitude entails a lower inspired PO2.
The resulting hypoxia stimulates breathing through the peripheral chemoreceptors. The increase in ventilation leads to a reduction in blood PCO2 and an increase in blood and CSF pH, which opposes the initial stimulation of
breathing. After a few days, the pH of the CSF recovers through compensatory changes in CSF bicarbonate and the major opposition to the hypoxic stimulation of breathing is eliminated. The blood pH also recovers through the excretion of bicarbonate by the kidneys, eliminating the
suppression of peripheral chemoreceptor activity. These changes allow ventilation to increase above the initial value, allowing blood O2 to rise above initial levels

7

Describe the integrated response to exercise in terms of the control of respiration.

The increase in arterial PCO2 and the resulting decrease in pH lead to activation of chemoreceptors, which in turn send signals to the respiratory center in the brain to increase ventilation. The increase in ventilation is accomplished by both increases in breathing frequency and tidal volume.

8

Describe the locations and functions of peripheral chemoreceptors.

Divided into two groups, the carotid and aortic chemoreceptors. Both groups are stimulated by decreases in arterial PO2 or increases in PCO2

Carotid: located in the carotid bodies, which are small nodules of tissue found bilaterally at the bifurcation of the common carotid arteries into the internal and external carotids. Stimulated by decreases in arterial pH. Sense the level of O2. Important during metabolic acid-base disturbances, as they are the sole detectors of arterial pH in the body that can mediate ventilatory changes.

Aortic: located in the aortic bodies, found around the arch of the aorta and between the arch of the aorta and the pulmonary artery.

9

Describe the location and functions of central chemoreceptors.

Situated close to the ventral surface of the medulla. They
bind to protons in the brain, but they are not sensitive to the level of protons in arterial blood, but instead arterial PCO2. CO2 first crosses the blood-brain barrier into the CSF, where it combines with water and dissociates into protons and bicarbonate. The chemoreceptors then bind the protons and stimulate breathing (increase ventilation (VA ).
There are no central chemoreceptors for oxygen

10

Understand the relative importance of peripheral or central chemoreceptors under different conditions

x

11

Describe the role of the blood-brain barrier in determining the function of central chemoreceptors.

x

12

Describe the integrated response to changes in altitude in terms of the control of respiration.

x

13

Describe the integrated response to exercise in terms of the control of respiration.

x