Control of Respiration

Question 1

What are the central chemoreceptors?

Answer 1

Located inside the brainstem, on the other side of the BBB

Sensitive to fluctuation of CO2

Question 2

What are the peripheral chemoreceptors?

Answer 2

Located in the neck

Respond to Arterial [H+], Arterial PCO2, Arterial PO2

Question 3

What is the principle controller of ventilation?

Answer 3

PaCO2 through central chemoreceptors

Increases respiratory drive when activated

Question 4

How does a change in PaCO2 activate the central chemoreceptors?

Answer 4

CO2 readily crosses the BBB and enters the CSF

In the CSF, undergoes conversion to H2CO3, then readily dissociates to H+ and bicarbonate

The increase in H+ activates the chemoreceptors, however they are also sensitive to very small increases in CO2

Question 5

What occurs in response to the activation of the central chemoreceptors?

Answer 5

Ventilation increases

The increase in ventilation causes PaCO2 to fall, and in turn, a rise in CSF pH back to normal. Central Chemoreceptors decrease firing, and ventilation goes back to normal

Question 6

Where are the peripheral chemoreceptors located and what do they respond to?

Answer 6

Carotid and aortic bodies

Both respond to changes in [H+]

Only the carotid bodies respond to low PO2

Question 7

Describe the shift in main respiratory drive during hypoxia.

Answer 7

In the case of hypoxia, if the PO2 falls below 60mmHg, the main respiratory drive shifts from PCO2 to fluctuation in PO2.

The effect of PCO2 still exists, its just the main drive is shifted to PO2

Response to hypoxia never adapts

Question 8

What is the most powerful stimulus on respiratory drive?

Answer 8

Concentration of hydrogen ions (pH) in arterial blood

Elevation of respiration in response to increase in arterial pH is mediated solely by peripheral chemoreceptors

Question 9

How do the responses to hypoxia and hypercapnia affect each other?

Answer 9

Hypercapnia or acidosis amplify the effects of hypoxia

The increase in ventilation to hypoxia is greater in the case of hypercapnia than when the PCO2 is normal

Question 10

What is the danger of treating a lung disease patient with ventilation?

Answer 10

Patient with a low V/Q mismatch will lead to hypoxemia and hypercapnia

Acidosis will be compensated for through renal compensatory mechanisms, meaning patient is only relying on hypoxic drive for ventilation

Giving oxygen can reduce this drive and cause depressing ventilation, must be monitored closely

Question 11

What is the role of the phrenic nerve in inspiration?

Answer 11

Innervates the diaphragm, exits from C3-C5

Question 12

What nerves control the accessory muscles for respiration?

Answer 12

Internal intercostals - thoacic nerves

Abdominal muscles - lumbar nerves

Trauma that results in damage to these regions can have major impacts on respiration

Question 13

What does the respiratory control center consist of?

Answer 13

Dorsal respiratory groups

Ventral respiratory groups

Located in the medulla

Question 14

What is the role of the dorsal respiratory groups in respiration?

Answer 14

Consists chiefly of inspiratory neurons that control the diaphragm and intercostals

Receives input from peripheral and central chemoreceptors, stretch receptors and higher brain centers

Responsible for the basic rhythm of breathing, triggers inspiration at a rate of 12-15 breaths/minute

Question 15

What is the role of the ventral respiratory groups in respiration?

Answer 15

Contains both inspiratory and expiratory neurons

Controls the constituent muscles of the upper airways that regulate the diameter of the upper airways during breathing

Also controls the muscles of exhalation and accessory muscles of inspiration

Question 16

What is the Apneustic Center?

Answer 16

Located in the Pons, continually sends neural impulses to stimulate inspiratory neurons of DRG and VRG

Question 17

What is Apneustic Breathing?

Answer 17

Respiratory cycle holds in inspiration which is periodically interrupted by expiration

Results from cutting the pons, removing the pneumotaxic center and vagus nerve

Question 18

Where is the pneumotaxic center and what are its major functions?

Answer 18

Located in the Pns

Prevent aneupsis

Enhance and fine-tune the rhythmicity of breathing

Question 19

What is congenital central hypoventilation syndrome (CCHS)?

Answer 19

Central pattern generator is inoperative due to the insensitivity of chemoreceptors to CO2, O2, and pH

Automatic breathing is lost, Voluntary breathing is intact

Danger is sleep and loss of consciousness

Treated with a permanent tracheostomy that is connected to a ventilator during sleep

Question 20

What conditions alter respiratory control in the medulla?

Answer 20

Cerebral edema

Intracerebral Abnormality

Acute Poliomyelitis

CNS depressants and stimulants

Question 21

What is the difference between the effect of mild and severe hypothermia on respiration?

Answer 21

Mild increases ventilation due to sympathetic nervous system as the body works to preserve heat

Severe hypothermia depresses ventilation as a result of general of neural activity

Question 22

What is Cheyne-Stokes breathing?

Answer 22

10-30 seconds of apnea followed by gradual increase in volume and frequency of breathing until another period of apnea occurs

Question 23

What is Biot’s respiration?

Answer 23

Characterized by rhythmic but deep respiration movements which alternate with long respiratory pauses

Occurs in meningitis patients and disorders of cerebral circulation

Also associated trauma and opioid use

Question 24

What is obstructive sleep apnea?

Answer 24

Upper airway is obstructed because there is too much fat around the pharynx

Severity measured by the Apnea/Hypopnea index

Question 25

What is central sleep apnea?

Answer 25

Characterized by a normal deep inspiratory cycle interchanged with complete cessation of breathing

Typically a problem with control of respiration

Different from Cheyne-Stokes because there is no hyperventilation and waning of ventilation

Question 26

What is Kussmaul’s respiration?

Answer 26

Hyperventilation, gasping, deep and labored respiration

Usually seen in DKA, kidney failure, or other states characterized by a high degree of acidosis