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Biol 1412 > Topic 13 > Flashcards

Topic 13 Flashcards

1
Q

3 processes involved in exchange of air

A
  • pulmonary ventilation
  • external respiration
  • internal respiration
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2
Q

Pulmonary ventilation

A

result of pressure gradients caused by changed in thoracic cavity volume.

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3
Q

Boyles Law

A

gas volume is inversely proportional to pressure. as volume increase pressure decrease (vice versa) for the same number of molecules of air (gas amount is constant)

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4
Q

3 pressures involved in pulmonary ventilation

A
  • P atm: atmospheric (760 mmHg) sea level
  • P pul: intrapulmonary: air pressure inside lungs (= P atm between breaths)
  • P ip: intrapleural: fluid pressure in pleural cavity
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5
Q

Intrapleural pressure is ..

A
  • always < P pul
  • usually < P atm (just slightly, 756 mmHg)
  • throacic wall recoils, out lungs recoil in but fluid holds them together so P ip decreases slightly
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6
Q

Quiet inspiration

A

active process (muscles contract). at start P atm =P pul (760 mmHg). no air moves then..

  • diaphragm, ext intercostals contract (active) , ⇑ vol. of thoracic cavity
  • lungs resist expansion ∴ Pip ⇓ (756⇒754 mmHg)
  • higher pressure difference between Ppul and Pip pushes lungs out ⇒ lungs expand ∴ Ppul ⇓ (760 ⇒ 758 mmHg)
  • air moves in down P gradient (until Ppul = Patm)
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7
Q

Forced inspiration

A

active process.diaphragm, external intercostals + sternocleidomastoids, pectoralis minors, scalenes contract (∴ active).⇑⇑ vol. of thoracic cavity ∴ pressure gradient ⇑, and
more air moves in

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8
Q

Quiet expiration

A
  • relax diaphragm, ext. intercostals ⇒ lungs to resting size ∴ ⇓ thoracic cavity size (passive process)
  • vol ⇓, Pip ⇑ (754 ⇒756 mmHg) ∴ Ppul ⇑ (760⇒762 mmHg) ⇒ air moves out down pressure gradient
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9
Q

Forced expiration

A
  • laboured or impeded (e.g. asthma) breathing
  • relax diaphragm, ext. intercostals + contract internal intercostals, abdominals (active process)
  • Pip ⇑ ⇒ lung volume ⇓ ∴ Ppul ⇑ and air moves out
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10
Q

Stretch in lungs determined by either..

A
  • compliance

- recoil

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11
Q

Compliance

A

effort needed to stretch lungs; low = much effort

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12
Q

Recoil

A

ability to return to resting size after stretch

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13
Q

Both compliance and recoil =

A

result of elastic CT + surfactant

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14
Q

Lungs collapse prevented by..

A
  • P ip is always below P pul

- Presence of surfactant

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15
Q

Pneumothorax

A

air in pleural cavity. Patm = Pip = Ppul so lungs collapse, thoracic wall expands

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16
Q

Surfactant= Lipoprotein / phospholipid mixture

A
  • in watery film coating alveoli (decrease surface tension)
  • allows easier stretch of lungs (increase compliance)
  • prevents alveolar collapse
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17
Q

Respiratory distress syndrome

A

newborns to 7 months gestation. inadequate surfactant so alveoli tend to collapse (love compliance) so effort is high which leds to death

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18
Q

Air flow and airway resistance equation

A 
F= air flow
P= Patm - Ppul
R= airway resistance
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19
Q

Airway resistance determined by diameter of bronchi and bronchioles so..

A

-inspiratory mechanics open airways/ expiratory close always.

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20
Q

SNS dilates..

A

bronchiolar smooth muscle

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21
Q

PSNS

A

contracts it (bronchocontriction)

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22
Q

Asthma, bronchitis, emphysema increase airway resistance so..

A

more difficult to expire than to inspire

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23
Q

Respiratory volumes used measuring..

A

spirometer

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24
Q

1 respiration =

A

1 inspiration + 1 expiration

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25
Q

Tidal volume (TV)

A

inspired or expired air during quiet respiration (500 ml)

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26
Q

Inspiratory reserve volume (IRV)

A

excess air over TV take in on a max inspiration (3000 ml)

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27
Q

Expiratory reserve volume (ERV)

A

excess air over TV pushed out on max expiration (1200 ml)

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28
Q

Residual volume (RV)

A

volume of air in lungs after maximal expiration (1200 ml)

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29
Q

Minute respiratory volume

A

TV x respiratory rate (ex: 500 ml x 12 breaths/min = 6L/ min)

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30
Q

Forced expiratory volume in 1 second (FEV1)

A

volume expired in 1 sec with max effort, following max inspiration

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31
Q

Lung capacity

A

2 or more volumes

32
Q

Inspiratory capacity (IC)

A

= IC + IRV

33
Q

Vital capacity (VC)

A

= TV + IRV + ERV (largest volume in and out of lungs)

34
Q

Total lung capacity (TLC)

A

= TV + IRV + ERV + RV (= VC + RV) ** max amount of air lungs can hold

35
Q

FEV1 measured while..

A

measuring VC and expressed as %VC (allows correction for body size) usually FEV1 = 80% VC

36
Q

Measurements of lung capacity allows for diagnoses of..

A
  • obstructive disorders

- restrictive disorders

37
Q

Obstructive disorders

A

hard to expire = high R. therefore RV high, VC low, and FEV1 < 80% VC. (ex: emphysema, asthma, cystic fibrosis)

38
Q

Restrictive disorders

A

restrict lung expansion, hard to inspire. therefore IC low, VC low, FEV1 low (but FEV1 = 80% VC) (ex: scoliosis, pneumothorax)

39
Q

External respiration

A

O2 from alveoli to blood and CO2 from blood to alveoli

40
Q

External respiration aided by..

A
  • thin respiratory membrane (2 cells + basement membrane)
  • large surface area: capillaries, alveoli and rbc single file in capillaries ∴ max rbc exposure to gases
  • blood velocity slow compared to gas diffusion (rbc have time to pick up/release gases)
41
Q

Internal respiration

A

O2 from blood to cells and CO2 from cells to blood

42
Q

Partial pressure of gases =

A

the pressure exerted by a single gas in a mixture of gases (ex: O2 = 21% of air). written as P o2, P co2, P n2, etc. pressure gradients promote gas movements from high to low pressure

43
Q

Partial P =

A

0.21 x 760 mm Hg = 160 mmHg

44
Q

O2 carried in 2 ways either.

A
  • dissolved in plasma (1.5%) (=Po2)

- bound to hemoglobin (98.5)

45
Q

O2 dissolved in plasma at lung capillaries (external)

A

O2 moves from high pressure (105 mmHg in the lungs/alveoli) to low pressure (40 mmHg in the capillary)

46
Q

O2 dissolved in plasma at tissue capillaries

A

arterial Po2 = mmHg. resting venous + ISF P o2 = 40 mmHg. ICF Po2 < 40 mmHg. O2 diffuses: capillary to ISF to cell (down P gradient)

47
Q

O2 dissolved bound to hemoglobin

A

each hemoglobin (Hb) can bind to 4 O2 molecules (1 O2/Fe)

48
Q

Plateau on the O2 Hb dissociation curve (between 60 and 100 mmHg Po2)

A

= range of PO2 in lung at which Hb picks up O2 (Hb 97% saturated)

  • if alveolar PO2 ⇓ a little below normal ⇒ little change in Hb saturation
  • e.g. at high altitude ⇒ if alveolar PO2 above 60 mm Hg ⇒ Hb carries normal amount of O2
49
Q

Steep portion on the O2 Hb dissociation curve at rest

A
  • range of PO2 in tissues - O2 unloaded from Hb
  • ISF PO2 = 40 mm Hg ⇒ Hb = 75% saturated (97-75 = 22% unloaded to cells)
  • allows holding of breath
50
Q

Steep portion on the O2 Hb dissociation curve at high metabolism

A

(e.g. exercise): ISF PO2 = 20 mm Hg ⇒ Hb = 40% saturated (97% - 40% = 57% of O2 unloaded): or more

51
Q

Shift to the right on the O2 Hb dissociation curve

A

for a given PO2, get less Hb saturation i.e. O2 unloads more easily/loads less easily

52
Q

Shift to the right on the O2 Hb dissociation curve occurs when..

A

– ⇑ PCO2
– ⇓ pH (related to ⇑ CO2, also lactic acid) = decreased ability of O2 to bind to Hb when H+ is bound to globin (= Bohr effect)
– ⇑ temp.
§ All occur when ⇑ cell metabolism e.g. exercise - Hb releases more O2

53
Q

Shift to the left on the O2 Hb dissociation curve

A

For a given PO2, get more Hb saturation i.e. O2 loads more easily/unloads less easily

54
Q

Shift to the left on the O2 Hb dissociation curve occurs when..

A

– ⇓ PCO2
– higher pH
– ⇓ temp.
§ = conditions at lung (⇓ temp. due to evaporative cooling)

55
Q

CO2 carried in 3 ways

A
  • dissolved in plasma = 8%
  • bound to hemoglobin = 20%
  • as bicarbonate ions = 72%
56
Q

CO2 dissolved in plasma at the lungs (external)

A
  • alveolar PCO2 = 40 mmHg
  • resting venous PCO2 = 45 mmHg
  • arterial PCO2 = 40 mmHg
    § CO2 diffuses: capillary → alveolus
57
Q

CO2 dissolved in the plasma at the tissue (internal)

A
  • arterial PCO2 = 40 mmHg
  • ICF PCO2 > 45 mmHg
  • ISF PCO2 = 45 mmHg
  • resting venous PCO2 = 45 mmHg
    § CO2 diffuses: cell → ISF → capillary
58
Q

CO2 bound to hemoglobin

A

=carbamino Hb (CO2 on global) .CO2 binds to deoxyHb better than to oxyHb ∴ Hb binds CO2 readily at the tissues

59
Q

CO2 carried as a bicarbonate can be either..

A
  • inside RBC at tissues (high CO2)

- inside RBC at lungs

60
Q

Respiratory centres in medulla

A

set rate ad depth of breathing

61
Q

2 groups of neurons in the respiratoy centre of medulla

A
  • ventral (VRG)

- dorsal (DRG)

62
Q

VRG

A

generates rate, expiratory and inspiratory neurons

63
Q

DRG

A

receives chemoreceptor input and modifies VRG output

64
Q

Inspiratory neurons

A

impulses down spinal cord to the phrenic nerve (innervates diaphragm) or the thoracic nerves (innervate intercostals_

65
Q

Expiratory neurons

A

fire to inhibit insp. neurons and expiration occurs passively

66
Q

Quiet breathing VRG

A
  • Insp. neurons active ∼ 2 sec = insp.
  • expir. neurons inhibit inspir. neurons’ output ∼3 sec = expir.
  • VRG also active for forced insp. and expir., to recruit the additional muscles
  • respiration may cease if VRG damaged or suppressed e.g. by alcohol, morphine
67
Q

Pontine respiratory centres

A

work w medullary centres to make breathing smooth, even. damage can cause gasping or irregular

68
Q

Lung stretch receptors

A

in smooth muscle of bronchi and bronchioles. the Hering Breuer reflex

69
Q

Voluntary control of respiration

A
  • 1⁰ motor cortex to skeletal muscle (corticospinal pathway) and bypass medulla
  • if medulla damaged, must remember to breathe
  • hold breath - ⇑ PCO2 - medulla overrides voluntary control ⇒ breathe
70
Q

Peripheral chemoreceptors

A

carotid and aortic bodies. not sensitive to P co2. very sensitive to H+, If blood H+ ⇑ (⇓ pH) ⇒ vent rate ⇑ (+ vice versa). PO2 - stimulates receptors when PO2 reaches ∼ 50-60 mmHg (end of plateau of Hb-O2 curve), emergency situation. PO2 ⇓ due to lung disease, low atm PO2

71
Q

Central chemoreceptors- medullae oblongata (dominant control)

A

respond indirectly to arterial P co2. resting arterial P co2 = 40 mmHg. (set point 37-43) CO2 crosses blood brain barrier easily (H, HCO3 don’t). CSF poorly buffered, small change is stim response

72
Q

Hyperventilation

A

⇓ arterial PCO2 ⇒ cerebral vasocon (intrinsic metabolic response) ∴ ⇓ PO2 to brain ⇒ dizziness

73
Q

Hypoventilation

A

⇑ arterial PCO2, ⇑ H+ = acidosis ⇒ CNS confusion

74
Q

CO poisoning

A

CO binds 210x more strongly to Fe than O2 – forms carboxyHb (HbCO), result: ⇓ total O2. no change in PO2 or PCO2 (dissolved gases) ∴ ventilation rate doesn’t change

75
Q

CO in environment

A

incomplete burning of gas (cars, furnaces), coal, wood, cigarettes

Biol 1412 (15 decks)

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