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Respiratory Physiology > Breathing > Flashcards

Breathing Flashcards

1
Q

What is the volume of air inhaled/exhaled per minute?

A

5 litres

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2
Q

Define transpulmonary pressure.

A

Difference in pressure between the inside and outside of the lung

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3
Q

How do you calculate transpulmonary pressure?

A

Alveolar pressure - intrapleural pressure

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4
Q

Define intrapleural pressure.

A

The pressure in the pleural space

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5
Q

Define alveolar pressure.

A

Air pressure in the alveoli

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6
Q

Describe the steps of inspiration.

A
  1. Diaphragm contracts, moves down and causes thorax volume to increase
  2. External intercostal muscles contract, causing the ribs to move upward and outward. This further increases thoracic volume
  3. As the thorax expands, the intrapleural pressure is lowered and transpulmonary pressure increases - causing lung expansion
  4. Lung expansion causes alveolar pressure to become negative. This results in inward airflow.
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7
Q

Describe the steps of passive expiration.

A
  1. Motor neurones to diaphragm and external intercostal muscles reduce their firing so the muscles relax. Diaphragm ascends, decreasing thoracic volume.
  2. Lungs and chest walls passively collapse due to elastic recoil. Transpulmonary pressure decreases due to increased intrapleural pressure
  3. As the lungs become smaller, the alveolar pressure exceeds atmospheric pressure. This results in the outflow of air
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8
Q

Describe the steps of forced expiration.

A
  1. Internal intercostal muscles contract
  2. Causes ribs to move downwards and inwards. This actively decreases thoracic volume
  3. Abdominal muscles contract, forcing the diaphragm up further and decreasing thoracic volume even more
  4. Results in more air being expired
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9
Q

When does forced expiration occur?

A

During exercise

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10
Q

Which airway provides the greatest resistance to air being breathed in or out?

A

Trachea. Although bronchioles are the smallest, there are many of them and they provide a much larger surface area so have less resistance.

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11
Q

What is dead space?

A

The volume of air not contributing to ventilation.

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12
Q

How much total dead space is there?

A

175ml

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13
Q

Which part of the brain controls breathing?

A

Respiratory centre in the medulla

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14
Q

Name the two groups of neurones in the respiratory centre.

A

Dorsal respiratory group

Ventral respiratory group

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15
Q

Describe the role of neurones in the dorsal respiratory group.

A
  • Primarily fire during inspiration.

- Fire impulses to spinal motor neurones that activate cause contraction of diaphragm and external intercostal muscles

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16
Q

Describe the role of neurones in the ventral respiratory group.

A
  • Neurones fire during active expiration and quiet inspiration
  • Send impulses to cause contraction of expiratory muscles
  • Houses respiratory rhythm generator in pre-Botzinger complex
  • Respiratory rhythm generator is composed of pacemaker cells that set the basal respiratory rate
17
Q

Where do medullary inspiratory neurones receive synaptic input from?

A

Pons

18
Q

Which area of the pons fine tunes the output of inspiratory neurones in the medulla?

A

Apneustic centre

19
Q

Which area can override the apneustic centre?

A

Pneumotaxic centre

20
Q

Which area acts to smooth the transition between inspiration and expiration? It also switches off inspiratory neurones to prevent hyperinflation.

A

Pneumotaxic centre. Also known as pontine respiratory group.

21
Q

Name the pulmonary stretch receptors.

A
  1. Slowly adapting stretch receptors
  2. Rapidly adapting stretch receptors
  3. C fibre J receptors
22
Q

Describe the role of slowly adapting stretch receptors.

A
  • activated by lung distension
  • high activity inhibits further inspiration, begins expiration
  • if inflation is maintained, they slowly adapt to low frequency firing
23
Q

Where are slowly adapting stretch receptors found?

A

Smooth muscle of airway

24
Q

Describe the role of rapidly adapting stretch receptors.

A
  • activated by lung distension and irritants
  • produce brief burst of activity
  • high activity causes bronchoconstriction
  • respond at the onset of stimulus but very quickly cease responding
25
Q

Where are rapidly adapting stretch receptors found?

A

Between airway epithelial cells

26
Q

Describe the role of C fibre J receptors.

A
  • stimulated by an increase in lung interstitial pressure (caused by fluid e.g. pulmonary embolism)
  • activity results in rapid breathing (tachypena), bronchoconstriction, dry cough
  • gives rise to the sensation of pressure in the chest - makes breathing feel difficult
27
Q

Where are C fibre J receptors found?

A

Capillary walls or interstitium

28
Q

Which pulmonary stretch receptors are myelinated?

A
  1. Slowly adapting stretch receptors

2. Rapidly adapting stretch receptors

29
Q

Which pulmonary stretch receptors are non-myelinated?

A

C fibre J receptors

30
Q

Where are peripheral chemoreceptors found?

A
  1. At the bifurcation of the common carotid arteries. They are called carotid bodies
  2. On the arch of the aorta. They are called aortic bodies here.
31
Q

What are the peripheral chemoreceptors stimulated by?

A
  1. Decrease in PaO2

2. Increase in arterial H+

32
Q

Name the predominant peripheral chemoreceptor involved in the control of respiration.

A

Carotid body

33
Q

How do the peripheral chemoreceptors respond to reductions in PaO2?

A

Fire impulses to Type II cells > Type II cells release neurotransmitters that stimulate the carotid sinus nerve > This nerve provides excitatory synaptic input to medullary inspiratory neurones

34
Q

At what value of PaO2 stimulates the peripheral chemoreceptors to fire?

A

60mmHg or less

35
Q

Where are central chemoreceptors located?

A

Medulla

36
Q

What stimulates central chemoreceptors?

A

Increase in H+ concentration (via PaCO2) in CSF

37
Q

How do the central chemoreceptors respond to increased H+?

A

Provide excitatory synaptic input to the medullary inspiratory neurones. A very small increase in PaCO2 causes a reflex increase in ventilation.

38
Q

Which nerve supplies the diaphragm?

A

Phrenic nerve

39
Q

Name accessory inspiratory muscles.

A

Sternocleidomastoid

Pectoralis major and minor

Respiratory Physiology (11 decks)

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