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Physiology of human organ systems > Respiratory > Flashcards

Respiratory Flashcards

1
Q

What are T1 surfactant cells and what do they do?

A

These are the alveolar cells where the gaseous exchange actually occurs and are largely responsible for the large surface area.

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2
Q

What are T2 surfactant cells and what do they do?

A

These cells are dispersed between the T1 cells and are responsible for secreting the surfactant that covers the inside of the lungs

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3
Q

Which part of the airway has the highest resistance?

A

The bronchi

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4
Q

What is functional reserve volume?

A

The remaining volume of the lungs after a normal breathe has been exhaled.

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5
Q

What is the residual volume?

A

The volume in the lungs after a big breathe- it cannot become smaller even no matter how hard they try.

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6
Q

What is the reserve volume?

A

The difference in volume between a normal breathe and the largest breathe possible.

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7
Q

What is the vital capacity?

A

The maximum volume that can be exhaled.

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8
Q

What is the difference between a volume and a capacity?

A

A capacity is when several volumes are added/subtracted to form one number.

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9
Q

What is the purpose of residual volume?

A

To prevent alveolar collapse

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10
Q

What is the purpose of pleural fluid?

A

To provide lubrication between the two parts of the pleural membrane and to act as a force to keep them stuck together. The latter prevents lung collapse.

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11
Q

What does Henry’s law say about dissolved gases?

A

the amount of gas dissolved in a liquid is determined by the [partial] pressure of the gas and its solubility in the liquid.

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12
Q

Which muscles are involved in inspiration?

A

The diaphragm, rectus abdominis and the internal intercostals

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13
Q

Which muscles are involved in expiration?

A

External intercostal muscles, Sternocleidomastoid and scalene.

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14
Q

In terms or rib movement, how does pump handle action increase the volume?

A

It increases the anterior posterior dimension.

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15
Q

In terms of rib movement, how does the bucket handle action increase the volume?

A

It increases the lateral dimensions.

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16
Q

What is the intrathoracic pressure?

A

Pressure inside the lungs or alveoli

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17
Q

What is the intrapleural pressure?

A

The pressure in the pleural cavity (between the two layers of the pleura)

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18
Q

What is the transpulmonary pressure?

A

The pressure difference between the thoracic and pleural pressures.

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19
Q

What is the purpose of lung surfactant?

A

It acts as a detergent and decreases the surface tension over the lungs. This reduces the likelihood of alveoli collapsing in and sticking to themselves and others.

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20
Q

What is lung compliance?

A

The ability for the lung to expand and distense.

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21
Q

How and why does the surfactant affect the compliance?

A

It increases the compliance as the alveoli aren’t sticking together as much, less force or effort is required to pull them apart and expand the lungs.

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22
Q

At which level is the surfactant most effective?

A

The alveolar level as the surface tension is proportionally greater on smaller surface

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23
Q

What happens when neonates don’t have or have insufficient surfactant?

A

They suffer from infant respiratory distress syndrome (IRDS)

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24
Q

What is IRDS?

A

Air requires more energy to inflate the lungs (as it is compressible) therefore, more effort is required on the babies’ behalf to inflate them. If the baby does not have surfactant, it will seriously struggle to complete this.

25
Q

What can decrease the proportion of dead space?

A

Increasing the usable alveolar volume.

26
Q

How does hypoventilation affect P(A)O2 and P(A)CO2?

A

This slowed breathing means not much ventilation is occurring and the alveolar volume is not expanding and the proportion of dead space is not decreasing. This means less gaseous exchange is occurring and P(A)O2 decreases and P(A)CO2 increases.

27
Q

Why does the base of the lung have slightly higher compliance?

A

Because it is slightly compressed by the diaphragm.

28
Q

What is the bronchial circulation?

A

Systemic circulation to the lungs

29
Q

At which rib level is V/Q precisely matched (ratio 1:1)?

A

Around rib 3.

30
Q

Where is perfusion are ventilation at its highest point?

A

At the base of the lung.

31
Q

Where is the largest V/Q mismatch found?

A

At the apex of the lung?

32
Q

Why is the largest V/Q mismatch found in the apex?

A

Whilst both decrease going from the base superiorly, the perfusion decreases much more rapidly until it is much lower than the ventilation. This is largely due to the effect of gravity increasing perfusion.

33
Q

What happens to P(A)CO2 when perfusion exceeds ventilation?

A

It increases as the pressure forces the CO2 out and the lungs cannot ventilate the CO2 out quickly enough.

34
Q

What happens to P(A)O2 when perfusion exceeds ventilation?

A

It decreases because the lungs cannot ventilate new oxygen into the alveoli quickly enough to replace the oxygen diffused into the arterial blood.

35
Q

What happens when to P(A)CO2 when ventilation exceeds perfusion?

A

It decreases because the lungs ventilate away the CO2 more quickly than it is replaced by perfusion.

36
Q

What happens to P(A)O2 when ventilation exceeds perfusion?

A

It increases because the lungs ventilate oxygen into the alveoli more quickly than it diffuses into and is taken away by the perfusion.

37
Q

What happens when blood passes through the pulmonary circulation without significant gas exchange occuring?

A

Shunting

38
Q

What is the respiratory sinus arrythmia?

A

The synchronous and continually varying respiratory and heart rate.

39
Q

How is oxygen delivery to tissues calculated?

A

Arterial plasma and Hb O2 content x cardiac output

40
Q

When at rest, how much of the oxygen is taken out of Hb into tissues?

A

25%

41
Q

What is co-operative binding?

A

Each time an oxygen molecule binds to Hb, Hb undergoes a conformational change making it harder for the next oxygen molecule to bind to Hb.

42
Q

How does CO2 alter Hb’s affinity for O2?

A

It causes a conformational change meaning it has a lower affinity to O2. This means that it is more likely to offload O2 in high concetrations of CO2.

43
Q

What will happen to the O2-Hb dissociation curve in higher concentrations of CO2/H+?

A

It will move the curve to the right.

44
Q

What does 2,3-DPG do the the O2-Hb dissociation curve?

A

It moves it to the left.

45
Q

When and why is 2,3-DPG secreted?

A

It is secreted in low PO2 situations. Its purpose is to increase Hb affinity to O2 meaning it is more likely to bind at lower partial pressures.

46
Q

How much of an affinity to Hb does CO have?

A

250x greater than O2.

47
Q

What is the innervation of the diaphragm?

A

The phrenic nerves.

48
Q

What is the innervation of the intercostal muscles?

A

Intercostal nerves

49
Q

What sets the intrinsic rhythm for breathing?

A

The pons and medulla.

50
Q

What can modulate the intrinsic respiratory rhythm?

A

Emotional, voluntary and mechanosensory input.

51
Q

What are the dorsal respiratory group neurons responsible for?

A

The main muscles of inspiration.

52
Q

What are the ventral respiratory group neurons responsible for?

A

Innervating the oro-pharynx-larynx and expiratory muscles.

53
Q

What is hypercapnea?

A

Increased blood CO2

54
Q

What effect on respiratory rate and tidal volume do most anaesthetics have?

A

They decrease tidal volume and increase respiratory rate.

55
Q

What is the sequence of events that can occur in response to barbiturate/opioid depression of the respiratory centres?

A

They decrease the sensitivity to CSF [H+] and this reduces the respiratory drive. They also reduce the sensitivity to peripheral PO2 receptors. This lack of control over respiration can result in respiratory failure and death.

56
Q

What happens to PCO2 sensitivity in people with chronic lung disease?

A

It decreases the sensitivity, meaning the person will rely on the peripheral PO2 as their primary respiratory drive.

57
Q

Why is nitrous oxide dangerous for people with chronic lung disease?

A

N2O reduces the sensitivity of peripheral PO2 sensors- this is okay in most people as it is their secondary respiratory drive. However, someone with this disease relys on PO2 sensors as their primary respiratory drive. The lack of respiratory control can result in respiratory failure.

58
Q

What happens when the rate of metabolism and ventilation are not matched?

A

They risk metabolic acidosis or alkalosis. This is because the respiratory system is a key part of plasma pH managment. If the ventilation exceeds metabolism, it will increase the pH and if metabolism exceeds ventilation then pH will increase.

Physiology of human organ systems (5 decks)

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