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Human Body Systems II (BMSC 208) > Module 2: Respiratory II > Flashcards

Module 2: Respiratory II Flashcards

1
Q

What two factors keep PO2 and PCO2 values relatively constant during quiet respiration?

A
  1. O2 intake = O2 uptake
  2. Fresh air is diluted upon entering the lungs
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2
Q

Hyperventilation causes a _____ in PO2 and a _____ in PCO2.

A

Increase, decrease.

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3
Q

Hypoventilation causes a _____ in PO2 and a _____ in PCO2.

A

Decrease, increase.

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4
Q

Ventilation and perfusion must be matched, why?

A

Blood flow must be high enough to pick up the available O2, otherwise there will be wasted ventilation/perfusion.

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5
Q

What acts as a form of local regional control to ensure ventilation and perfusion are matched? Where is blood flow higher?

A

Gravity. Blood flow is higher at the base of the lung.

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6
Q

What two structures in the lungs act as a form of local control to ensure ventilation and perfusion are matched? What are each primarily influenced by and how?

A
  1. Pulmonary arterioles
    • O2 sensitive primarily
      • Decrease O2: constriction
      • Increase O2: weak dilation
      • Decrease CO2: weak dilation
      • Increase CO2: weak constriction
  2. Bronchioles
    • CO2 sensitive primarily
      • Decrease CO2: constrict
      • Increase CO2: dilate
      • Decrease O2: weak constriction
      • Increase O2: weak dilation
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7
Q

Hypoxia is often paired with what?

A

Hypercapnia.

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8
Q

To avoid hypoxia and hypercapnia, sensors monitor the arterial blood and respond to these three variables:

A
  1. Oxygen
  2. pH
  3. Carbon dioxide
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9
Q

What are the three determinants of alveolar gas exchange? Put the key two first, and describe what each is determined by.

A
  1. O2 reaching the alveoli
    • Composition of inspired air
    • Alveolar ventilation
      • Rate and depth of breathing
      • Airway resistance
      • Lung compliance
  2. Gas diffusion between the alveoli and blood
    • Partial pressure gradient
    • Surface area
    • Diffusion distance
      • Barrier thickness
      • Amount of fluid
  3. Adequate perfusion of alveoli
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10
Q

When hypoxia is caused by inadequate amounts of oxygen reaching the alveoli, what are the two causes (assuming perfusion remains constant)?

A
  1. Inspired air has low oxygen content
    • Altitude
  2. Alveolar ventilation
    • Increased airway resistance
    • Decreased lung compliance
    • CNS issue
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11
Q

If perfusion remains constant and hypoxia is not caused by hypoventilation or alterations in atmospheric PO2, the problem usually lies within what?

A

Gas exchange between the alveoli and blood.

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12
Q

What 4 factors affect the random movement of gas molecules between the alveoli and capillaries?

A
  1. Concentration gradient
  2. Surface area
  3. Barrier permeability (determined by solubility of gas)
  4. Diffusion distance
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13
Q

In a healthy individual, what is the main determinant of diffusion?

A

Concentration gradient.

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14
Q

What effect does emphysema have on alveolar gas diffusion?

A

Decreased surface area.

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15
Q

What effect does fibrotic lung disease have on alveolar gas diffusion?

A

Decreased barrier permeability.

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16
Q

What effect does pulmonary edema have on alveolar gas diffusion?

A

Increased diffusion distance.

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17
Q

The movement of gas molecules from air to liquid is directly proportional to what three factors?

A
  1. Pressure gradient of the gas
  2. Solubility of gas in liquid
  3. Temperature
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18
Q

Which gas is very soluble in liquid? Which is not?

A

CO2 is very soluble, O2 is not very soluble.

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19
Q

The Fick equation explains what? What is the formula for the Fick equation?

A

The O2 consumption by systemic tissues. The equation is:

QO2 = arterial O2 transport - venous O2 transport

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20
Q

Of the oxygen in the blood, what percent is bound to hemoglobin and what percent is dissolved in plasma?

A

98% is bound to hemoglobin and less than 2% is dissolved in plasma.

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21
Q

During oxygen binding, as the concentration of free O2 increases, what happens? Where in the body will this occur? Up until what point will this process occur?

A

More oxygen binds to hemoglobin producing oxyhemoglobin (HbO2). This will occur in the lungs, and will continue until equilibrium between the plasma and Hb.

22
Q

During oxygen binding, as the concentration of free O2 decreases, what happens? Where will this happen in the body?

A

O2 will release from hemoglobin and enter the plasma to enter the cells. This happens at the tissues.

23
Q

Plasma O2 is determined by alveolar PO2, which depends on what 3 factors?

A
  1. Composition of inspired air
  2. Alveolar ventilation rate
  3. Efficiency of gas exchange
24
Q

A lower pH will have what effect on oxygen’s release from hemoglobin?

A

It will increase O2 release.

25
Q

A higher PCO2 will have what effect on oxygen’s release from hemoglobin? Why? What effect does this contribute to?

A

It will increase O2 release. It is readily converted to acid, contributing to the Bohr effect.

26
Q

A lower temperature will have what effect on oxygen’s release from hemoglobin? Why?

A

Decreased O2 release. Temperature causes conformational changes leading to affinity changes.

27
Q

A lower 2,3-BPG level will have what effect on oxygen’s release from hemoglobin?

A

Decreased O2 release.

28
Q

Adult hemoglobin is composed of _____ and _____ subunits, while fetal hemoglobin is composed of _____ and _____ subunits. Of the two _____ hemoglobin has higher oxygen affinity.

A

Alpha, beta, alpha, gamma, fetal.

29
Q

Why is removing carbon dioxide from the body so important? What can this condition lead to?

A

Elevated PCO2 causes acidosis, which when too severe causes CNS depression leading to confusion, coma, or death.

30
Q

Of the CO2 in the blood, what is the breakdown of transport?

A
  • Plasma: 7%
  • Red blood cells: 93%
    • Hemoglobin: 23%
    • Bicarbonate (HCO3): 70%
31
Q

What two purposes does bicarbonate serve?

A
  1. Additional means of CO2 transport from the cells to the lungs
  2. Buffer system
32
Q

Which enzyme catalyzes the change from CO2 to HCO3?

A

Carbonic anhydrase.

33
Q

To prevent equilibriation between CO2, HCO3 and H+, what two mechanisms exist?

A
  1. HCO3/Cl exchanger: can run either direction
  2. Hemoglobin acts as a buffer to bind excess H+ ions
34
Q

When hemoglobin and carbon dioxide bind, what is formed? Where on the hemoglobin does CO2 bind?

A

Carbaminohemoglobin. CO2 binds at exposed amino groups.

35
Q

Starting from HCO3 entering the RBC via HCO3​/Cl exchanger, how will CO2 enter the alveoli? During this process what will happen to the CO2 within the cell and how will it adjust? To what point will this adjustment continue?

A
  1. HCO3 will be converted to H2CO3 and split into H2O and CO2.
  2. CO2 will diffuse from the cell into the plasma.
  3. CO2 will diffuse from plasma to alveoli.

During this process the CO2 - HCO3 equilibrium is disturbed, which will cause the reaction to reverse, reversing the HCO3​/Cl exchanger as well. This will continue until equilibrium.

36
Q

What is the current model for respiration? (4 parts)

A
  1. Respiratory neurons in the medulla: control inspiratory and expiratory muscles.
  2. Neurons in the pons: integrate sensory information and interact with medullary neurons to influence ventilation.
  3. Medullary pacemaker spontaneously discharges signals creating rhythmic pattern of breathing.
  4. Chemoreceptors, mechanoreceptors, and higher brain centers: modulate ventilation
37
Q

Nucleus tractus solitaris (NTS)

  1. Where:
  2. Contains:
  3. Controls (via what):
  4. Recieves input from:
A
  1. In the medulla.
  2. Contains the dorsal respiratory group.
  3. Controls inspiratory muscles via phrenic and intercostal nerve.
  4. Recieves input from peripheral mechanoreceptors and chemoreceptors.
38
Q

Pontine respiratory group (PRG)

  1. Where:
  2. Role:
    • Does it create rhythm?
  3. Recieves input from:
A
  1. Pons.
  2. Provides tonic input to DRG to help medullary networks coordinate a smooth rhythm.
    • Does not create rhythm.
  3. Recieves sensory input from DRG.
39
Q

Ventral respiratory group (VRG)

  1. Where:
  2. Contains (does what):
  3. Controls:
A
  1. Medulla.
  2. Pre-Bötzinger complex: contains pacemaker neurons which may initiate respiration (ramping: shut off by pons).
  3. Muscles of active inspiration and expiration, remain quiet otherwise. Outputs keep airways open.
40
Q

CO2, O2 and pH influence ventilation by acting on these, located on the _____ and _____.

A

Peripheral chemoreceptors. Aorta and carotid artery.

41
Q

What part of the peripheral chemoreceptor is responsible for sensing the changes? What does it typically synapse to? What kind of channel is involved in responding to changes in pH, O2 or CO2?

A

Type I (glomus) cell. Usually synapses on a sensory neuron. K+ channels.

42
Q

What size drop in arterial PO2 will trigger peripheral chemoreceptors? How will the K+ channels act?

A

A large drop. K+ channels will close, leading to depolarization, triggering calcium channels, causing the release of NT’s.

43
Q

What feature of the glomus cell allows it to be exposed to blood?

A

Sinusoidal capillaries.

44
Q

Central chemoreceptors

  1. Location
  2. Provide input to:
  3. Respond to:
    • What feature of the neurons in these regions allow the input?
A
  1. Located in the medulla.
  2. Provide input to respiratory control center.
  3. Respond to pH changes in the CSF.
    • H+ sensitive channels (ASIC) become activated and transmit AP’s to the respiratory control center.
45
Q

Chemoreceptor responses: decreased arterial O2

  1. Primary chemoreceptor
  2. Pressure action (when will it start working)
  3. Mechanism
A
  1. Peripheral chemoreceptor (carotid body important).
  2. 60 mmHg.
  3. Increased contractions, increasing ventilation, return to normal.
46
Q

Chemoreceptor responses: increased arterial H+ (independent of CO2)

  1. Primary chemoreceptor
  2. Mechanism
A
  1. Peripheral chemoreceptor.
  2. Increased contractions, increased ventilation (decreases PCO2 in alveoli and arteries), return to normal.
47
Q

Chemoreceptor responses: increased arterial CO2

  1. Primary chemoreceptor
  2. Mechanism
A
  1. Both central (70%) and peripheral (30%) chemoreceptors.
  2. Both will increase contractions, increasing ventilation, returning to normal.
48
Q

What are the two protective reflexes that protect the lungs?

A
  1. Irritant receptors: respond to particles or gases.
    • Bronchoconstriction leading to rapid shallow breathing.
    • Can induce coughing or sneezing.
  2. Stretch receptors: prevent over inflation of the lungs.
    • Hering-Breuer initiation reflex.
49
Q

Ventilation rate can increase _____ fold during exercise, while PCO2, PO2 and [H+] remain relatively constant.

A

20.

50
Q

Ventilation rate jumps as soon as exercise begins, suggesting a _____ component to the ventilatory response. This could be caused by these:

A

Feedforward. Proprioceptors in the muscles and joints.

Human Body Systems II (BMSC 208) (11 decks)

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