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DPT 6150 Human Physiology > Human Physiology > Flashcards

Human Physiology Flashcards

respiratory physiology

1
Q

What is the shape of the oxyhemoglobin dissociation curve?

A

sigmoidal

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2
Q

why is the oxyhemoglobin dissociation curve sigmoidal in shape

A

due to cooperative binding, where oxygen binding to hemoglobin increases its affinity for more oxygen

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3
Q

at what PaO2 range does hemoglobin remain almost 100% saturated

A

60-100 mmHg

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4
Q

what does sigmoidal shape of the curve indicate about oxygen binding?

A

small changes in PaO2 at high levels (above 60 mmHg) do not significantly affect hemoglobin saturation

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5
Q

Why can the body tolerate a drop in PaO₂ to 60 mmHg without significantly reducing hemoglobin saturation?

A

Because hemoglobin remains nearly fully saturated (~90%) within this range.

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6
Q

What is the significance of the steep portion of the oxyhemoglobin dissociation curve?

A

Small decreases in PaO₂ lead to large oxygen unloading, which is beneficial for tissues needing oxygen.

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7
Q

What happens when the curve shifts to the right?

A

Hemoglobin has a lower affinity for oxygen, promoting oxygen unloading in tissues

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8
Q

What happens when the curve shifts to the left?

A

Hemoglobin has a higher affinity for oxygen, making it harder to release oxygen to tissues.

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9
Q

what happens to the V/Q ratio in pulmonary embolism

A

It becomes infinite (V/Q = ∞) because perfusion (Q) is 0.

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10
Q

What physiological response occurs in response to pulmonary embolism?

A

Compensatory bronchoconstriction to reroute air away from unperfused regions.

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11
Q

What happens to the V/Q ratio in airway obstruction?

A

It becomes 0 (V/Q = 0) because ventilation (V) is absent

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12
Q

What physiological response occurs in response to airway obstruction?

A

Hypoxic vasoconstriction to reroute blood away from poorly oxygenated regions.

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13
Q

Why does hypoxic vasoconstriction occur in airway obstruction?

A

To divert blood flow away from areas without proper ventilation and direct it to better-oxygenated regions

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14
Q

What is the normal V/Q ratio for the entire lung?

A

~0.8

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15
Q

which lung zone has the highest V/Q ratio

A

zone 1

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16
Q

which lung zone has the smallest V/Q ratio

A

zone 3

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17
Q

why is the V/Q ratio highest in lung zone 1

A

Due to relatively lower perfusion compared to ventilation, as gravity limits blood flow to the apex

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18
Q

why is the V/Q ratio lowest in lung zone 3?

A

Because blood flow (perfusion) is highest due to gravity, outweighing the effects of ventilation.

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19
Q

What are the two main centers of the medullary respiratory center?

A

The inspiratory center and the expiratory center

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20
Q

What is the function of the inspiratory center in the medulla?

A

It sends motor output to the diaphragm via the phrenic nerve, initiating inspiration.

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21
Q

When is the expiratory center active?

A

It is quiet at rest but becomes active during exercise to enhance expiration.

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22
Q

What is the function of the apneustic center?

A

It stimulates the medullary inspiratory center to increase inspiration duration and decrease expiration.

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23
Q

What is the primary role of chemoreceptors in respiration?

A

To detect changes in CO₂, O₂, and pH and adjust breathing accordingly

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24
Q

What is the function of lung stretch receptors?

A

They decrease inspiratory drive when stretched, preventing overinflation of the lungs.

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25
What reflex is mediated by lung stretch receptors?
The Hering-Breuer reflex, which inhibits excessive lung expansion.
26
What is the function of juxtacapillary (J) receptors in the lungs?
They detect pulmonary capillary enlargement, such as in heart failure (HF), and increase the rate of inspiration.
26
Where are mechanoreceptors in muscles located, and what do they do?
Located in skeletal muscles and joints, they respond to movement by stimulating inspiration.
27
How do juxtacapillary (J) receptors contribute to dyspnea in heart failure?
They increase the respiratory rate in response to fluid accumulation in the alveoli, causing rapid, shallow breathing.
28
Strong response to changes in pH and control regular minute-to-minute breathing rate
central chemoreceptors (brainstem)
29
Respond to significant decreases in PO2 below 60mmHg (<90% SpO2 )
peripheral chemoreceptors
30
Turns off inspiration to limit tidal volume and respiratory rate
pneumotaxic center
31
epresent blood that passes through a cardiac defect from the right side of the heart to the left, resulting in hypoxemia, and cannot be corrected by inhaling 100% oxygen
right-to-left shunt
32
are more common and represent oxygenated blood that flows from the left side of the heart back to the right side, which does not result in hypoxemia but will result in the right-sided cardiac output being greater than left
left-to-right shunts
33
What is pulmonary blood flow autoregulation?
The body's response to hypoxia by inducing bronchoconstriction educe blood flow to areas that are not adequately oxygenated (<70mmHg).
34
What happens to blood flow in Zone 1 of the lungs?
Minimal perfusion due to blood flow autoregulation. Primarily occurs during diseased states.
35
What happens to blood flow in Zone 2 of the lungs?
Intermittent flow in the middle and upper lungs
36
What happens to blood flow in Zone 3 of the lungs?
Constant flow in the lower area of the lungs
37
How does body position affect lung perfusion?
In a supine position, all lung zones act like Zone 3, since the lungs are at the same level as the heart, ensuring even perfusion
38
↑PCO2 , ↓pH, ↑temperature, ↑2,3 DPG
right ward shift
39
hemoglobin offloading at a given PO 2 is increased or decreased
increased
40
↓ PCO₂, ↑ pH (alkalosis), ↓ temperature, ↓ 2,3-DPG.
leftward shift
41
This chemical transport is primarily transported via hemoglobin (98%); only small amounts are unbound (2%), but the unbound oxygen is the only part that contributes to partial pressures
oxygen
42
This chemical transport is also transported via hemoglobin, making them competitive binding sitesand why CO poisoning occurs
carbon dioxide
43
This chemical transport is primarily transported via transformation to bicarbonate (HCO3- ,90%) with small amounts dissolved or bound to Hg
carbon monoxide
44
What does diffusion-limited gas exchange mean?
will reach equilibrium by the time blood exits the capillary.
45
Which gas is diffusion-limited in healthy individuals at rest
carbon monoxide
46
What does perfusion-limited gas exchange mean?
Gas equilibrates quickly, and the only way to increase exchange is by increasing blood flow.
47
Which gases are normally perfusion-limited?
O₂ and CO₂ in healthy individuals.
48
What is the equation for Fick’s Law of Diffusion?
Diffusion Rate = (Diffusion Coefficient × Membrane Surface Area × Partial Pressure Difference) / Membrane Thickness
49
Which gas has a higher diffusion coefficient, O₂ or CO₂?
CO₂ has a >20x greater diffusion coefficient than O₂.
50
How does the partial pressure gradient affect O₂ diffusion?
High alveolar O₂ pressure promotes O₂ diffusion into mixed venous blood.
51
How does the partial pressure gradient affect CO₂ diffusion?
Higher venous PCO₂ promotes CO₂ diffusion into the alveoli for exhalation.
52
volume of air in the lungs and airways that do not participate in gas exchange
dead space
53
Volume of the conducting airways, ~150 mL
anatomical dead space
54
Total volume of the lungs that does not participate in gas exchange. Includes ventilated alveoli without perfusion
physiologic dead space
55
(tidal volume – dead space) * respiratory rate
alveolar ventilation
56
primary muscles of inspration
Diaphragm: Depresses to increase volume
57
what are the accessory muscles of inspiration
External intercostals, scalene, SCM
58
what is the mechanics of inspiration
bucket handle & water pump
59
Passive expiration normally Muscles: Internal intercostals, abdominal muscles (Rectus abdominus, internal and external oblique, transversus abdominus)
expiration
60
Explain the anatomical structure and function relationships of the upper and lower components of the respiratory system
Branching tree anatomy allows for large volumes at alveoli for diffusion
61
trachea, bronchi, non-respiratory bronchioles
conducting zones
62
respiratory bronchioles, alveolar ducts, alveolar sacs
respiratory zones
63
Normal FEV1 /FVC ratio
0.8
64
stimulates muscarinic receptors, causing bronchoconstriction
PSNS
65
stimulates β2 receptors, causing bronchodilation
SNS
66
as you inhale, the lungs expand, creating increased inward pressure to recoil/collapse
lung
67
naturally inclined to expand
chest wall
68
-5 cmH2 0 normally, which helps counteract the lungs’ elastic recoil and keep it open
intrapleural pressure
69
vary between 8-25 mmHg depending on systole or diastole
pulmonary arteries BP
70
-5 cmH2 0 intrapleural pressure and no significant elastic recoil leads to alveoli wanting to expand
rest
71
the PA decreases to about -1cmH2 O, but the intrapleural pressure decreases to up to -8 cmH2 O, leading to a larger net expansion force on the alveoli than at rest. Once alveoli expand during terminal inspiration and air flows in, the net PA reaches the equilibrium point of 0 cmH2 O.
inspiration
72
passive process driven by the elastic recoil of the lungs and chest wall increasing the pressure in the alveoli to +1 cmH2 O, and air flows out until pressure returns to 0 cmH2 O
expiration
73
positive pressure in the alveoli greatly increases up to +35 cmH2 O, and PI increases to +20 cmH2O
forced expiration
74
leads to a decreased ability to generate positive PA due to decreased compliance, which can lead to airway collapse during forced exhalation
emphysema
75
eleased from type 2 alveolar cells in response to stretch. It reduces surface tension by decreasing the density of water molecules at the air-water interface, thus increasing compliance and preventing collapse. As the alveoli expand, the density of surfactant decreases, providing a brake force to expansion
surfactant
76
Surfactant inactivated by
hypoxia, infection, or edema
77
500mL = volume of a normal breath
tidal volume
78
1.2 L = Lung volume that can be expelled after a normal exhalation
Expiratory reserve capacity
79
2.4 L = Lung volume after a normal exhalation
functional residual capacity
80
3 L = lung volume that remains to fill after a normal. breath in
inspiratory reserve
81
3.5 L = total volume from resting lungs to maximal inhalation
inspiratory capacity
82
1.2 L = volume of the lungs that does not participate in gas exchange
residual volume
83
4.8 L = Maximal amount of air exchange volume; TLC – residual volume
vital capacity
84
6 L = total volume of the lungs
total lung capacity

DPT 6150 Human Physiology (1 decks)

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