Control of Ventilation

Question 1

What part of the CNS contains the central pattern generator for breathing?

Answer 1

Brainstem (medulla)

Question 2

Control of Ventilation/Respiration is regulated through

Answer 2

negative feedback system in three basic elements:

1. Central Controller (medulla, pons)
2. Effectors (respiratory muscles)
3. Sensors (chemoreceptors)

Question 3

Emotional status and voluntary input can affect breathing rate (True or False)

Answer 3

True

Question 4

Basic principles of respiration were first established by who?

Answer 4

Galen of Pergamon (2nd century) while studying gladiator injuries

Question 5

The neurons in the medulla are mainly divided into what two groups?

Answer 5

1. Dorsal Respiratory Group (DRG)

2. Ventral Respiratory Group (VRG)

Question 6

Which respiratory group contains BOTH inspiratory and expiratory neurons; project to phrenic, intercostals and abdominal neurons?

Answer 6

VRG

Question 7

Which respiratory group contains the Botzinger complex (site where normal breathing rhythm originates)?

Answer 7

VRG

Question 8

Breathing rhythm activity of the pre-Botzinger complex is relayed to the roots of _________ cranial nerve and then finally related to the _______ via that nerve.

Answer 8

• Hypoglossal nerve

- breathing muscles (muscles of the tongue, nares, and pharynx)

Question 9

Hypoglossal nerve is ___th cranial nerve

Answer 9

12

Question 10

Respiratory group that has the Nucleus Tractus Solitarius

Answer 10

Dorsal Respiratory Group

Question 11

Respiratory group that contains mainly INSPIRATORY neurons; main SENSORY nucleus (receives inputs from peripheral receptors); some neurons project directly to motor neurons that control respiratory muscles

Answer 11

Dorsal Respiratory Group

Question 12

located in the pons (PRG); center that can cause gasping (apnuestic breathing); NOT essential for normal respiratory rhythm, but can modulate

Answer 12

Apneustic Center

Question 13

located in the pons (PRG); center that promotes rhythmic breathing; NOT essential for normal respiratory rhythm, but can modulate

Answer 13

Pneumotaxic Center

Question 14

Prolonged inspiration and short expiration; gasping

Answer 14

Apneustic breathing

Question 15

What are the major effector (motor) neurons that innervate the respiratory muscles?

Answer 15

1. Phrenic Motor Neurons: located in C2-C5 and project to diaphragm
2. Thoracic Motor Neurons: located in T1-T12 and project to intercostals
3. Lumbar Motor Neurons: located in lumbar region and project to abdominals

Question 16

Injury above or at ______ requires permanent mechanical ventilator

Answer 16

C2-C5

Question 17

What are the major sensors of respiration?

Answer 17

1. Peripheral Chemoreceptors
2. The carotid body
3. Central Chemoreceptors
4. Pulmonary Stretch Receptors
5. Pulmonary Irritant Receptors
6. J Receptors
7. Others (PMP)

Question 18

What picks up changes in blood oxygen, carbon dioxide and pH?

Answer 18

Peripheral Chemoreceptors (located in carotid body and aortic arch)

Question 19

Afferent (sensory) fibers of the carotid body join with what cranial nerve to carry signals to the brain

Answer 19

Glossopharyngeal (IX)

Question 20

Main stimulus for peripheral chemoreceptors to increase firing in order to increase ventilation

Answer 20

PaO2 <60mmHg

Question 21

What would happen to the ventilatory response to low oxygen if nerve IX was damaged?

Answer 21

Glossopharyngeal nerve cannot carry signals to the brain, requiring mechanical ventilator

Question 22

chemoreceptor located at common carotid; has large and fenestrated blood supply; communicates with glossopharyngeal nerve (IX) to stimulate medullary centers and ventilation; mechanism of action may involve glomus cell

Answer 22

Carotid body

Question 23

Highly metabolic cells that require large amount of oxygen; low oxygen triggers secretion of neurotransmitters that activate glossopharyngeal nerve to stimulate medullary centers to increase ventilation

Answer 23

Glomus cell

Question 24

Acute exposure to low O2 results in

Answer 24

1. Rapid Hyperventilation (Increased amplitude and frequency of ventilation)
2. Decreased end tidal CO2 (enhanced ventilation eliminated excess CO2)
3. Sudden period of apnea (cessation of ventilation) when high O2 is administered.

Question 25

Decreasing percent O2 leads to

Answer 25

increased respiratory rate

Question 26

________ chemoreceptors mainly sense oxygen

Answer 26

Peripheral

Question 27

________ chemoreceptors mainly sense CO2 and H+ (pH)

Answer 27

Central

Question 28

When peripheral chemoreceptors are denervated, the response to CO2 and low pH remains intact thanks to central chemoreceptors (True or False)

Answer 28

True

Question 29

Chemoreceptors that are located in the ventrolateral medulla and in the raphe; sensitive to CO2 and pH; monitors via CSF status (Central or Peripheral)

Answer 29

Central Chemoreceptors

Question 30

CSF is made by and enters via _______ and drains via ______

Answer 30

choroid plexus; arachnoid villi

Question 31

What makes CSF sensitive to changes in CO2 (and therefore pH)?

Answer 31

The composition of CSF is controlled by the blood brain barrier, making CSF low protein content. This decreases buffering power of CSF and therefore changes in PaCO2 (and therefore pH as well) are readily reflected in the CSF.

Question 32

CSF pH is regulated by

Answer 32

PaCO2

Question 33

Increased _______ (shifts CO2 into making H+ and HCO3- by the kidneys) decreases pH, stimulating central chemoreceptors to drive ventilation

Answer 33

PaCO2

Question 34

CO2 at high levels has a _____ effect and may trigger severe hypoventilation

Answer 34

narcotic

Question 35

Why is CO2 such a good regulator for ventilation via the central chemoreceptors

Answer 35

Strong, inverse relationship between ventilation and CO2 (halving ventilation doubles CO2)

Question 36

Acute exposure to high CO2 results in

Answer 36

1. GRADUAL hyperventilation (gradual increased amplitude and frequency of ventilation) 2. Removal of high CO2 stimulus does NOT result in sudden apnea.

Question 37

Exposure to high CO2 results in ______ equilibration of CSF pH compared to exposure to low O2.

Answer 37

slower/gradual

Question 38

Why do changes in CO2 conc. have a gradual effect on ventilation?

Answer 38

Due to relatively slow equilibration of CSF pH versus rapid sensation of O2 by highly active carotid body

Question 39

receptors involved in ventilation control; located in airway smooth muscle (bronchioles); afferents via VAGUS nerve; stimulated by stretching and inhibits ventilation; protects lungs from overinflating

Answer 39

Pulmonary Stretch Receptors

Question 40

Reflex seen in pulmonary stretch receptors; stretching/overinflation stimulates receptors, inhibiting ventilation

Answer 40

Hering-Breuer reflex

Question 41

What receptors are "slowly adapting", meaning it maintains firing rate for entire length of stimulus (don't desensitize)?

Answer 41

Stretch Receptors

Question 42

Severing the vagus nerve would increase _____ since afferent input from pulmonary stretch receptors (which prevents over-inflation) is removed.

Answer 42

tidal volume

Question 43

Receptors involved in ventilation control; afferent innervation via myelinated VAGUS nerve; located in airway epithelial cells; stimulated by noxious gases, smoke, dust or cold air; increases ventilation, bronchoconstriction and coughing

Answer 43

Pulmonary Irritant Receptors

Question 44

What receptors are stimulated by histamine in asthma?

Answer 44

Irritant Receptors

Question 45

What receptors are "rapidly adapting", meaning it | desensitizes even while stimulus remains?

Answer 45

Irritant Receptors

Question 46

Receptors involved in ventilation control; via VAGUS nerve; located in pulmonary capillary external wall; rapid response to blood-borne substances (endotoxin), pulmonary congestion or edema; involved in dyspnea

Answer 46

Juxta-capillary "J" Receptors

Question 47

Activation of what receptors causes transient apnea followed by shallow breathing, bronchoconstriction, and mucus secretion?

Answer 47

Juxta-capillary "J" Receptors

Question 48

Receptor involved in dyspnea with pulmonary vascular congestion or edema, seen in Left sided HF and interstitial lung disease (ILD)

Answer 48

Juxta-capillary "J" Receptors

Question 49

Other receptors that play a role in coordination and regulation of ventilation, helping match ventilation to metabolic demands.

Answer 49

1. Thoracic wall and skeletal muscle spindles 2. Joint mechanoreceptors 3. Pain and temperature receptors

Question 50

the sensation of changes in body position and effort expended

Answer 50

proprioception

Question 51

Inputs from many of the peripheral and central receptors terminated in

Answer 51

DRG

Question 52

When PACO2 is increased at low PAO2, higher rates of ventilation are seen than at regular levels of PAO2 (True or False)

Answer 52

True

Question 53

When PAO2 becomes lower at high PACO2, higher rates of ventilation are seen than at normal levels of PACO2 (True or False)

Answer 53

True

Question 54

At normal levels of CO2, the response to hypoxia does not become profound until PAO2 is _______

Answer 54

less than 60 mmHg

Question 55

Significant increase in ventilation during exercise is not due to low O2, high CO2, or low pH (True or False)

Answer 55

True (still not well understood)

Question 56

Increased ventilation during exercise is initially driven by ___________, but during strenuous levels of exercise, ventilation is driven by ____________

Answer 56

- Anticipation from higher cortical centers and exercising muscles - low pH (due to lactic acid) when anaerobic threshold is reached

Question 57

______ cause alveolar and arterial PCO2 to rise and PO2 to decrease and arterial pH to decrease

Answer 57

Hypoventilation

Question 58

Causes of hypoventilation

Answer 58

- Drugs/anesthesia - CNS damage/disease (infection, ALS, trauma) - Muscular (myasthenia gravis, dystrophy) - Upper airway obstruction

Question 59

Where is the normal rhythm for ventilation believed to originate?

Answer 59

Pre-Botzinger Complex