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BIOM20002 - HSF > Lecture 57 - Control of Respiration > Flashcards

Lecture 57 - Control of Respiration Flashcards

1
Q

What organisms do we study to learn about respiratory control?

A

Brain damaged patients
Animals
Imaging techniques

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2
Q

What is the main function of the respiratory system?

A

Gas exchange (primary function)

Immune function
Reservoir for blood

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3
Q

What are the components of the respiratory system?

A

Lungs
Airways
Respiratory muscles

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4
Q

What are the groups of respiratory muscles?

A

Inspiration
Expiration
Accessory (not normally engaged)

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5
Q

What are the branches of control of the respiratory system?

A

1/ Chemical (pH, CO2, O2)

2/ Neural
controls muscle

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6
Q

Describe the path of oxygen

A
  1. Inhaled through airways down into alveoli
  2. Moves into blood at the alveoli
  3. Transport in blood back to heart, then pumped to the rest of the body
  4. Transport into target cells for cellular respiration
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7
Q

Why do we need control of the respiratory system?

A
  • Coordination
  • Adaption to give constant level
  • Adaption to increase supply when necessary
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8
Q

What is the pH of the blood?

A

7.4

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9
Q

Describe pressure of oxygen in the arteries and veins

A

Arteries: 95 mmHg
Veins: 40

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10
Q

Describe pressure of CO2 in the arteries and veins

A

Arteries: 40
Veins: 46

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11
Q

What are the muscles of inspiration?

A
  • Diaphragm
  • External intercostals

Accessory:

  • Sternocleido-mastoids
  • Scalenes
  • Alae nasi
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12
Q

What is the nerve supply of the diaphragm?

A

Phrenic nerves

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13
Q

What is the nerve supply of the intercostals?

A

Intercostal nerves

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14
Q

Describe expiration during quiet breathing

A

Passive

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15
Q

Describe how expiration occurs

A

Elastic recoil of inspiratory muscles and lung tissue

Some motor neuron activity: keeps intercostals contracted to keep flow slow and smooth

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16
Q

What happens during forced expiration?

A

Active process

Accessory muscles

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17
Q

What is happening during obstructive sleep apnoea

A

Cause:
Abnormal airway anatomy or obesity

When they sleep, they obstruct their airway
Hypoxia
Hypercapnia
Hypersomnolence

Treatment:
Use a mask that provides positive airway pressure

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18
Q

Which areas in the brain are involved in respiration?

A

Brain stem:
1/ Pons
2/ Medulla oblongata

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19
Q

Where are the dorsal and ventral respiratory groups?

A

Medulla oblongata

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20
Q

Describe the function of DRG?

A

Supplies muscles of inspiration
(diaphragm and intercostals)

Phrenic nerve and intercostal nerves

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21
Q

What is the function of the VRG?

A
  • Rhythmic pattern of breathing
  • Active expiration
  • Forced inspiration
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22
Q

How long does inspiration take?

A

2 seconds

Shorter than expiration

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23
Q

How long does passive expiration last?

24
Q

Describe the neural activity during inspiration and expiration

A

Inspiration:

  • much neural activity
  • positive feedback (aka rumping)
  • -> More and more neurons activated

Expiration:
- low neural activity

25
Q

What is the function of the pons?

A

Fine-tuning of respiration
(by integrating information from DRG)

Influence start and finish of ventilation

26
Q

Describe chemical control of ventilation

A

CO2, pH and O2 effect breathing

27
Q

What is minute ventilation?

A

Respiratory rate x tidal volume

28
Q

What is the effect of CO2 on respiration?

A

When CO2 becomes too high, minute ventilation increases

29
Q

Describe the relationship between pH and minute ventilation

A

As pH decreases, breathing rate increase

30
Q

What is the effect of oxygen on minute ventilation?

A

As O2 decreases, minute ventilation increases

less than 70 mmHg, it is stimulated

31
Q

Where are the chemoreceptors?

A

Peripheral chemoreceptors:

  • Carotid bodies
  • aortic arch

Central:
- ventral surface of medulla
(CO2, H+)

32
Q

What do the chemoreceptors detect?

A

Central:

  • CO2
  • H+

Peripheral:
- O2

33
Q

Describe what happens to CO2 in the blood

A
  1. High CO2 in blood
  2. Carbonic anhydrase action
  3. HCO3 and H+ produced
  4. H+ act on chemoreceptors
34
Q

Describe the response of the peripheral chemoreceptors to low O2

A
  1. Low O2 in blood and thus cells
  2. K+ channels close
  3. Cell depolarisation
  4. Calcium entry
  5. Release of neurotransmitters in vesicles
  6. Action potential in sensory nerve
  7. Integration in respiratory control centres
35
Q

What conditions will have very low O2?

A

Respiratory conditions

High altitude

36
Q

What are the cells of the carotid bodies?

A

Glomus cells

37
Q

What is COPD?

A

Chronic Obstructive Pulmonary Disease

  • Caused by smoking
  • Chemoreceptors adapt to chronic hypercapnia

Only peripheral chemoreceptors (which respond to low O2) are functional

38
Q

Which chemoreceptors respond to low O2 levels?

A

Only peripheral chemoreceptors

39
Q

When are higher centres of the brain engaged?

A

Voluntary control of ventilation

Fear
Excitement

40
Q

Which higher brain centres can control breathing?

A 
Cerebral cortex
Limbic system (hypothalamus, hippocampus, amygdala)
41
Q

Which receptors activate the Hering-Breuer reflex?

A

Pulmonary stretch receptors

42
Q

What are the protective reflexes?

A 
Bronconstriction reflex
Coughing, sneezing
Hering-Breuer reflex
Pain and temperature
Joint and muscle
43
Q

Describe the H-B reflex

A

Inflation reflex:
the longer inspiration takes, the longer expiration takes

Deflation reflex:
shorter period of expiration in response to shorter inhalation time

44
Q

Once information is sent to the medulla oblongata what happens?

A

Somatic motor neurons activated:

  • diaphragm
  • intercostals
  • abdominal muscles
  • scalene
  • steromastoids
45
Q

Which stimuli are integrated by higher centres?

A 
Pain
Body temp
Hormones
Pressure receptors
Mechanoreceptors
46
Q

What happens during exercise?

A
  1. Motor cortical activation
  2. Muscle afferents send information to brain –> increased breathing
  3. CO2 increase –> chemoreceptors
  4. K+ and H+ increase
  5. increased catecholamines and temperature

NB no role for O2

47
Q

What controls respiratory rhythm?

A

pre-Bötzinger complex in VRG of medulla

These are pacemaker cells

48
Q

How is respiration controlled in hospital?

A

There is a machine
Patient intubated and put to sleep
Gases administered
Breathing rate, ventilation, concentration of gases all controlled by this machine

Drugs administered for anaesthesia override the central control of breathing

49
Q

What are the muscles of expiration?

A

Internal intercostals

Abdominal muscles

50
Q

What is the role of the accessory muscles of inspiration?

A
  • Scalanes & Sternomastoids
    Raise sternum
  • Alae nasi
    Flaring of nostrils
51
Q

Describe the function of the PRG

A

Pontine respiratory group

Coordination of smooth muscle rhythm

52
Q

Describe the detection of CO2 by the central chemoreceptors

A
  1. H+ in CSF
  2. Bind to chemoreceptors on surface of cells
  3. Integration in respiratory control centres
  4. Increase in vetilation
53
Q

Describe the action of peripheral chemoreceptors in response to high CO2

A
  1. H+ in blood
  2. Acts on receptor on cell
  3. Sensory nerve to respiratory centres
  4. Increase in ventilation
54
Q

What is the name for increased depth of breathing?

A

Hyperpnoea

55
Q

We are at high altitude.
What happens to PO2 in the blood?
What does this trigger?

A

PO2 in the blood drops
Peripheral chemoreceptors activated

NB Central chemoreceptors only activated if PO2 drops below 60 mmHg

56
Q

Can central chemoreceptors detect PO2?

A

Not normally

In rare cases, PO2 drops below 60 mmHg they can

57
Q

We are at high altitude.

What happens to PCO2?

A

Decreases

Initially producing the same amount of CO2 by metabolism, but we are increasing ventilation, thus, PCO2 decreases

BIOM20002 - HSF (60 decks)

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