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IMED3001 > Controls of Ventilation > Flashcards

Controls of Ventilation Flashcards

1
Q

Where is breathing rhythm generated?

A

Medullary respiratory centers

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2
Q

Where do medullary respiratory centers receive their input to control respiration?

A

Chemoreceptors (Centrally in the medulla or peripherally from aortic and carotid chemoreceptors) Proprioceptors (All respiratory muscles have spindles and Golgi tendon organs) Airway receptors (upper and lower) Higher centers (limbic system, hypothalamus and cerebral cortex)

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3
Q

What higher centers cause gasping with certain emotions?

A

Limbic system and hypothalamus

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4
Q

Which part of the brain is responsible for conscious control of ventilation?

A

Cerebral cortex

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5
Q

What aspects of ventilation can be controlled?

A

Depth and Timing can both be controlled.

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6
Q

How is depth of breathing controlled?

A

Different centers control the muscles involved in tidal breathing to the ones involved in forced breathing. So different centers control different muscles. Depth is determined by how actively the respiratory center stimulates the respiratory muscles.

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7
Q

How is timing of breathing controlled?

A

Rate is determined by when and how long the inspiratory center is active

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8
Q

What does the pontine pneumotaxic center control?

A

Pontine respiratory centers controls breathing muscle movement

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9
Q

What does the pontine apneustic center control?

A

Apneustic center stops breathing

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10
Q

What are the medullary respiratory centers?

A

Dorsal and ventral respiratory group [DRG and VRG]

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11
Q

What are the respiratory centers in the pons?

A

Pneumotaxic center Apneustic center

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12
Q

What nerve controls diaphragm?

A

Phrenic nerve

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13
Q

What sets the rhythm of breathing?

A

pre-Botzinger group (spontaneously discharging neurons) this group communicates with Dorsal Respiratory group of medulla. Dorsal Respiratory Group (DRG) controls phrenic nerve action potentials sending repetitive bursts of inspiratory action potentials

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14
Q

What happens when diaphragm receives more action potentials?

A

Diaphragm contracts and inpiration results.

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15
Q

What happens when diaphragm receives less action potentials?

A

Diaphragm relaxes and expiration results.

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16
Q

What does the pre-Botzinger group do?

A

A set of pacemaker cells; only controls pace in certain circumstances

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17
Q

What causes basic inspiration rhythm?

A

pre-Botzinger group is active for a few seconds (~2 sec) causing diaphragm to actively contract and then is inactive for a few more seconds (~3 sec) causing the diaphragm to relax.

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18
Q

Where does Dorsal Respiratory Group get its input for tidal rhythm?

A

Higher centers (conscious control [not certain whether or not pre-botzinger group is involved] or emotional reaction) Pontine centers (apneustic/pneumotaxic) CNS and peripheral chemoreceptors (Blood CO2 and O2 levels) Respiratory muscles (feedback) Integrates all inputs into a basic rhythm

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19
Q

What brain center takes over during forced breathing?

A

Ventral Respiratory Group

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20
Q

Is the Ventral Respiratory Group active during quiet breathing?

A

No

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21
Q

What does VRG do?

A

Takes over from DRG to exert extra respiratory drive when more volume and frequency is required

22
Q

What is the major function of VRG?

A

Most active during exercise Contributes more to expiration than to inspiration because forced expiration requires more changes than forced inspiration

23
Q

What muscles act in forced inspiration?

A

Diaphragm External IC Sternocleidomastoid Pec minor Scalene muscles

24
Q

What muscles act in forced expiration?

A

Internal IC and abdominal muscles

25
Q

What do pontine respiratory centers do?

A

Influence/modify preBotzinger/DRG/VRG activity These groups do not use a switch on / switch off method of control. Instead they prolong or shorten duration of inspiration and expiration thus controlling the rate at which breathing is occuring.

26
Q

What does the pneumotaxic area of the pons control?

A

It limits inspiration. It causes shorter inspiration and thus increases rate of inspiration

27
Q

What does the apneustic area do?

A

It inhibits switching off of inspiration which prolongs inspiration and reduces rate of breathing.

28
Q

What do chemoreceptors measure?

A

O2 (poor ability to measure O2) CO2 (measured more often either directly or through the pH) Decrease in pH reflects CO2 retention, accumulation of lactic acid and excess ketone bodies in patients with diabetes.

29
Q

Where are chemoreceptors found?

A

Central chemoreceptors are located in the medulla which measure concentrations in CSF. Peripheral chemoreceptors in carotid and aortic receptors measure chemical concentrations in arterial blood

30
Q

Where in the medulla are central chemoreceptors located?

A

Beneath ventral surface of the medulla.

31
Q

What is the response of primary chemoreceptors to high H+ or high CO2?

A

They are very sensitive to these changes and respond by increasing the rate/depth of breathing

32
Q

What do primary chemoreceptors primarily pick up?

A

H+ changes; CO2 can diffuse accross BBB and H+ cannot which means changes in pH of the CSF are purely the result of CO2 that was added to the CSF There is Carbonic Anhydrase on the medulla surface which means the changes in CO2 concentration have a delayed effect on the receptors in the medulla.

33
Q

What do peripheral chemoreceptors detect?

A

They sense hypoxia mostly and are mildly sensitive to pH, Pco2 and temperature. Their thresholds are very high compared to those in the medulla.

34
Q

What cells of the carotid arteries and aorta are the peripheral chemoreceptors?

A

They are specialized glomus cells

35
Q

Which cranial nerve do Aortic chemoreceptors send sensory information to medulla through?

A

CNX (vagus nerve)

36
Q

Which cranial nerve do carotid chemoreceptors send sensory information to the medulla through?

A

CNIX (Glossopharyngeal Nerve)

37
Q

Which part of the carotid contains the chemoreceptors?

A

The fork of the common carotid

38
Q

When are peripheral chemoreceptors typically activated?

A

During severe hypoxaemia. Their action is very high threshold.

39
Q

Diagram of the chemoreceptor control of ventilation:

A
40
Q

What is the inflation reflex called?

A

Hering-Breuer Reflex

41
Q

What happens to breathing rate when body temperature is increased?

A

It increases

42
Q

What is the Hering Breuer reflex?

A

Reflex inhibition of inspiration in response to stretching of the lung pleurae.

43
Q

Diagram showing all the factors that can act on breathing:

A
44
Q

How does alveolar ventillation and CO2 change in response to exercise?

A

Alveolar ventillation increases rapidly thus decreasing the amount of CO2 initially in the blood due to it being expelled rapidly.

The green arrow after exercise indicates the point in which negative feedback post exercise catches up with the high rate of CO2 production post exercise.

45
Q

What happens to Alveolar CO2 in response to exercise?

A

Initially it drops dramatically due to increased ventillation rate causing rapid loss of CO2.

46
Q

What happens to arterial CO2 after exercise?

A

Drop in rate of ventillation causes CO2 to build up temporarily

47
Q

What happens to rate of ventillation if intensity of exercise is increased?

A

It increases linearly with the intensity

48
Q

During exercise what is the main drive for the higher intensity of breathing?

A

Most factors are in the brain which override the feedback from the chemoreceptors. (Venous CO2 does not matter)

49
Q

What factors cause increase in ventilation as exercise begins? What happens to these factors when exercise ends?

A

Brain (psychological stimuli and cortical activation of muscles of respiratory system and skeletal muscles)

Proprioceptor impulses which go to the respiratory centers

When exercise ends these factors shut off and feedback takes over

50
Q

Summary diagram:

A

IMED3001 (46 decks)

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