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Cardio-respiratory Studies 1 > Scenario 5 - Respiration > Flashcards

Scenario 5 - Respiration Flashcards

1
Q

what are the two types of alveolar cells? what do they do?

A

Type I cells - squamous pulmonary epithelium - form continuous lining of wall - MAIN SITE OF GAS EXCHANGE

Type II (Septal) Cells - between the type I cells - rounded cuboidal epithelium - free surfaces contain microvilli - SECRETE ALVEOLAR FLUID

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2
Q

What is the alveolar fluid?

A

keeps the surface between the cells, and the air, moist

produce surfactant - that maintains airway patency

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3
Q

what are the alveolar macrophages?

A

found within the wall of the alveolus - phagocytose fine dust and other debris

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4
Q

what is the role of fibroblasts in the alveolar wall?

A

production of reticular and elastic cells

under the type I pnuemocytes to produce the elastic basement membrane

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5
Q

What is the respiratory membrane?

A

where gaseous exchange occurs

  1. alveolar wall (type I and II pneumocytes, macrophages)
  2. epithelial basement membrane of the alveoli
  3. capillary basement membrane (usually fused with (2))
  4. capillary endothelium
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6
Q

What is the pore of Kohn?

A

collateral ventilation between the alveoli

inter-alveolar

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7
Q

what is the Channel of martin?

A

interbronchiolar colateral ventilation

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8
Q

what is the channel of Lambert?

A

bronchioalveolar colateral ventilation

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9
Q

what factors effect the rate of gaseous exchange

A 
Concentration gradient determined by:
- partial pressure gradient
- solubility of the gases
Surface area
respiratory membrane thickness
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10
Q

What is the effect of solubility of a gas on rate of exchange?

A

if dissolved in water, diffusion is more efficient

so more soluble = faster diffusion across the respiratory membrane

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11
Q

what is the percentage of nitrogen in:

(i) dry air
(ii) alveolar air

A

(i) 79%

(ii) 75%

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12
Q

what is the percentage of oxygen in:

(i) dry air
(ii) alveolar air

A

(i) 21%

(ii) 14%

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13
Q

what is the percentage of carbon dioxide in:

(i) dry air
(ii) alveolar air

A

(i) 0.04%

(ii) 5.3%

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14
Q

what is the percentage of water vapour in:

(i) dry air
(ii) alveolar air

A

(i) 0

(ii) 6.2%

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15
Q

What is the partial pressure of oxygen in the alveoli?

A

13.3 kPa

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16
Q

what is the partial pressure of carbon dioxide in the alveoli

A

5.3 kPa

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17
Q

how is oxygen transported?

A

mainly through binding to haemoglobin

1.5% disolved in plasma

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18
Q

what effects oxygen binding to haemaglobin

A

partial pressure of oxygen

  • when PO2 is high - in the lungs - O2 binds to Hb
  • when PO2 is low - in the respiring tissues - O2 dissociates from oxyHb
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19
Q

what does haemoglobin saturation mean?

A

the amount of haemoglobin with O2 bount

i.e. when Hb is low saturated - not a lot of O2 is bound to Hb

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20
Q

What is affinity of Hb?

A

the tightness with which Hb binds O2
i.e. high affinity - more tightly bound to O2
low affinity - O2 is released more readily

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21
Q

what does an oxygen dissociation curve show?

A

how saturated Hb is at different partial pressures of O2

so when PO2 is low, such as in deoxygenated blood - Hb is not very saturated

when PO2 is high - eg. oxygenated blood in systemic circulation, saturation of Hb is high

22
Q

what is the effect of acidity on the oxygen dissociation curve?

A

when pH decreases - suggests CO2 in the blood is high

causes Hb affinity for O2 to decrease - so O2 is released more readily

CURVE SHIFTS TO RIGHT

23
Q

what is normal pH?

A

7.4

24
Q

how does the shift caused by acidity help to return pH to normal?

A

oxy-Hb becomes deoxy-Hb - releasing oxygen

in the process, the oxygen binding site is replaced by binding of H+ ions - thus removing them from circulation and increasing pH

25
Q

What is the effect of haemaglobin binding CO2?

A

causes affinity for O2 to decrease - O2 dissociates more readily.

CURVE SHIFTS RIGHT

26
Q

why would there be a high concentration of H+ ions in circulation?

A

when CO2 is high, it reacts with H20 in the RBCs forming H2CO3 - which is unstable and forms H+ and HCO3-

HCO3- remains in RBC

H+ moves out into the blood

27
Q

what is the effect of temperature on oxygen dissosiation?

A

increased temp - faster chemical reactions - more metabolic products - decreased pH - more O2 disossiation

CURVE SHIFTS RIGHT

28
Q

What is the effect of BPG on oxygen dissosiation?

A

BPG formed by RBCs during glycolysis

binds to the beta globin chain go Hb

decreases affinity for O2 - more O2 released

CURVE SHIFTS RIGHT

29
Q

What would cause the oxygen dissosiation curve to shift lefT?

A

high pH, low temperature, low [BPG]

30
Q

what causes the Bohr Shift?

A

O2 dissosiates readily from Hb at higher PO2 due to acidity or high concentration of CO2.

31
Q

what are the main ways that CO2 is transported?

A

Disolved in plasma (7%)
Carboamino compounds (i.e. bound to Hb) - 23%
As bicarbonate ions (70%)

32
Q

how is carbon dioxide transported as carboamino compounds

A

CO2 binds to the terminal alpha and beta chains of Hb

particularly when PCO2 is high

33
Q

How is CO2 transported as bicarbonate ions?

A

CO2 + H2O –> H2CO3 –> H+ and HCO3-

mainly carried in the RBC as HCO3-
some HCO3- diffuses out in exchange with Cl- (THE CHLORIDE SHIFT) to be transported in plasma

34
Q

what is the Haldane effect?

A

the more oxy-Hb in the circulation, the lower the carrying capacity for CO2

if there is high deoxy-Hb, it can:

  • bind more CO2
  • bind more H+ ions

by binding H+, increases the concentration gradient between RBC and blood - so more H+ can be formed from CO2 in the RBC

NET EFFECT - when oxygen levels are low, ability to transport carbon dioxide is higher.

35
Q

what is daltons law?

A

determines partial pressure

a gas exerts its own pressure in a mixture of gases as if no other gases were present

36
Q

what is the rhythm for normal breathing?

A

2 second burst for inspiration and 3 second relaxation for exhilation

37
Q

where is the inspiratory burst initiated?

A

DRG - sends impulses to diaphragm via phrenic nerve
& sends impulses to external intercostals via intercostal nerves

VRG acts as a pacemaker - sending signals to the DRG to initiate inspiration

38
Q

where are the DRG and VRG found

A

in the medullary respiratory centre

39
Q

what is the role of the VRG

A

pacemaker to DRG in quiet breakting
send impulses to accessory muscles in forceful inhalation
and in forced exhalation when DRG is not firing

40
Q

where is the pneumotaxic centre and what is its role?

A

within the Pons

transmit impulses to the DRG in normal breathing

Modifies the basic rhythm formed by the VRG during complex breathing - e.g. exercise, speaking, sleeping

41
Q

what is the role of the apneustic centre

A

increases the length of inspiration when talking by feeding back to DRG - to cause forced inhalation, and VRG to activate accessory muscles.

42
Q

what is the role of chemoreceptors?

A

detect pH of the blood - if low, then CO2 must be high

input to VRG - causing forced exhalation to blow off more CO2

43
Q

where are the central chemoreceptors?

A

within the medulla - CO2 diffuses into CSF - effects pH - central chemoreceptors feed to VRG directly

80% of response to high CO2

44
Q

where are the peripheral chemoreceptors

A

in the carotid and aortic bodies

45
Q

how do the peripheral chemoreceptors respond?

A

monitor pH, O2 and CO2

Carotid body –> glossopharangeal nerve –> DRG
Aortic body –> vagus nerve –> DRG

46
Q

what is the role of stretch mechanoreceptors?

A

found in smooth bronchiole walls

detect stretching to prevent over inflation of the lungs

feed back to DRG via vagus nerve - causing shorter and shallower breathing

47
Q

what is the role of J receptors?

A

found in alveolar and bronchiole walls
respond to lack of movement in the alveoli or bronchi

feed back to DRG via vagus nerve
increase rate and depth of breathing

48
Q

what is the role of proprioceptors?

A

within all respiratory muscles except the diaphragm

detect the position and length of the muscles - feed back to DRG to increase rate of breathing if the muscles are excessively stretched - i.e. in exercise

49
Q

what is the role of cortical control in breathing

A

higher centres detect anxiety, talking exercise etc.

input to the pons to modulate breathing

50
Q

what is VO2?

A

oxygen consumption

the amount of oxygen being used by the tissues per minute

51
Q

what is DO2?

A

oxygen delivery

the amount of oxygen being delivered to the tissues per minute

Cardio-respiratory Studies 1 (5 decks)

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