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Physiology > Blood Gas Transport & Blood Gases > Flashcards

Blood Gas Transport & Blood Gases Flashcards

1
Q

What are the forms that gases are carried in?

A

-Dissolved in plasma
-Chemically combined with haemoglobin
-Converted into a different molecule

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2
Q

Flow of oxygenated blood from heart?

A

Supplies tissues - back to heart - the to lungs

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3
Q

What are the 2 types of respiration?

A

-External
-Internal

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4
Q

Where does external respiration occur?

A

At lungs (alveoli)
(At level of lungs - alveoli)

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5
Q

Where does internal respiration occur?

A

At body tissues - from systemic capillaries into cells of body for O2 and from cells to capillaries for CO2
(At level of rest of the body)

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6
Q

What allows external respiration to occur?

A

Partial pressure gradients of O2 & CO2 - so diffusion occurs
-O2 from high PO2 in alveoli to lower PO2 in blood
-CO2 from high PCO2 in blood to lower PCO2 in lungs (alveoli)

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7
Q

Where are partial pressure gradients found?

A

Throughout respiratory system & tissues!

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8
Q

Describe external respiration - O2 diffusion?

A

O2 diffuses along its partial pressure gradient from alveolus to blood (pulmonary cap) –> until equilibrium is reached
(Facilitated by thin simple squam ep of alveoli - thin 1 cell thick - short diff pathway)

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9
Q

Describe external respiration - CO2 diffusion?

A

CO2 diffuses along its partial pressure gradient from blood (pulmonary cap) to alveolus –> until equilibrium is reached (so can exhale CO2)

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10
Q

What factors influence external respiration?

A

-SA & structure of resp membrane
-Partial pressure gradients (O2 & CO2) - throughout resp system
-Matching alveolar airflow to pulmonary blood capillary flow (matching ventilation w/ rate blood flows through caps)

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11
Q

What occurs in internal respiration?

A

-O2 diffuses from systemic capillaries into cells
-CO2 – cells to capillaries
(Delivering of O2 to cells & removal of CO2 - biproduct of cellular resp)

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12
Q

What is internal respiration dependent on?

A

-Available surface area
-Partial pressure gradients (O2 & CO2) - throughout resp system
-Rate of blood flow (metabolic rate of tissue)

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13
Q

What cells are involved in internal respiration?

A

-Myofibers
-Adipocytes
-Epithelial cells
-Immune cells

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14
Q

Why does O2 diffuse into the tissues as blood arrives at the capillaries?

A

-Due to PO2 gradient
-And due to affinity of haemoglobin for O2 - lowered (so unloads)

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15
Q

Overview of internal & external respiration & the partial pressure gradients that occur throughout?

A
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16
Q

How is O2 transported once they reach the blood (pulmonary capillary)?

A

1.5% 02 dissolves in the plasma
98.5% combines with haemoglobin (MOST)

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17
Q

What is haemoglobin, & what does it do?

A

-4 polypeptide chains - x2 alpha & x2 beta
-Transports O2 - O2 binds to the haem/iron groups (X4)
-So 1 haemoglobin can transport up to 4 O2 molecules

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18
Q

When is haemoglobin said fully saturated?

A

When 4 O2s are bound

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19
Q

When is haemoglobin said partially saturated?

A

When fewer than 4 O2s are bound

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20
Q

What is the key important factor around the binding of O2 to haemoglobin?

A

It is a reversible reaction

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21
Q

What is oxyhaemoglobin?

A

HbO2 - when O2 is bound to haemoglobin

22
Q

Where is oxyhaemoglobin found?

A

-‘Made’ in lungs
-‘Used’ in tissues

23
Q

What is deoxyhaemoglobin?

A

Hb - when NO O2 is bound to haemoglobin

24
Q

Where is deoxyhaemoglobin found?

A

-‘Formed’ at tissues
-‘Re-oxy’ at lungs

25
Q

What is high affinity, & where is it found?

A

-Readily binds/associates with O2
-Doesn’t readily dissociate from O2
–> haemoglobin = high affinity @ lungs (external)

26
Q

What is low affinity, & where is it found?

A

-Doesn’t readily bind/associate with O2
-Readily dissociates from O2
–> haemoglobin = low affinity @ body tissues (internal)

27
Q

When will oxyhaemoglobin form?

A

At high O2 concs/partial pressures - lungs (as association of oxygen occurs)

28
Q

When will deoxyhaemoglobin form?

A

At low O2 concs/partial pressures - body tissues (as dissociation of oxygen occurs)

29
Q

Describe the oxyhaemoglobin dissociation curve?

A

-Venous blood entering pulmonary caps = low PO2 - 40 mmHg
*= bottom of curve (at tissues) - curve reduces moving away from alveoli - as O2 is removed
-Alveoli = high PO2 - 100 mmHg
*= top of curve
–> so is a partial pressure gradient for O2 = diffusion occurs - giving 97% saturated haemoglobin

30
Q

Why might the oxyhaemoglobin dissociation curve be less steep as ‘tails’ off?

A

Small dec. in PO2 as moves into tissues - as get unloading of O2 into tissues

31
Q

Compare PO2 & haemoglobin saturation at sea level and at high altitudes (elevations)?

A

-Lungs at sea level: PO2 =100mmHg & haemoglobin = 98% saturated
-Lungs at high elevations: PO2 = 80mmHg (lower), haemoglobin = 95% saturated (slightly lower)

–>When PO2 in lung declines below typical sea level values – Hb still has high affinity for O2 so remains almost fully saturated

32
Q

Why else might haemoglobin saturation be low?

A

During vigorous exercise - actively contracting muscles use more O2 - so has lower PO2 in body (20 mmHg) so haem = only 35% saturated
-When PO2 = 40 mmHg, haemoglobin has lower affinity for O2 – 75% saturated
-Think on a scale as PO2 in body decreases (as exercise more & more) - the saturation of haemoglobin w/ O2 decreases too

33
Q

What is 2,3-Bisphosphoglyceric acid (BPG)?

A

-Present in RBCs……………………………….

34
Q

What factors can cause shift of the oxyhaemoglobin dissociation curve to the right?

A

-Decrease in pH (as muscle cells get more acidic)
-Increase in temp (from muscle contraction)
-Increased PCO2 (from muscles)
-Increase of a by-product of glycolysis = 2,3-BPG

35
Q

Why is the Bohr effect helpful for aerobic exercise?

A

When the curve shifts to the RIGHT in the Bohr effect - blood is RELEASING MORE OXYGEN to tissues (i.e. muscles) for Aerobic Exercise!

36
Q

What factors can cause shift of the oxyhaemoglobin dissociation curve to the left?

A

-Increased pH (dec H+)
-Decreased PCO2
-Decreased BPG (2,3-Bisphosphoglyceric acid)
-Decreased temp

37
Q

How does decreased PCO2 affect affinity?

A

= Higher affinity - as curve shifts to left - so O2 readily loaded

38
Q

How does increased PCO2 affect affinity?

A

= Lower affinity - as curve shifts right - so O2 is more readily unloaded into tissues

39
Q

Which - inc/dec is the Bohr shift/effect?

A

Increased PCO2 - due to action of H+ con/gradients

40
Q

Summarise what the Bohr effect/shift is?

A

-When PCO2 increases - when exercise
-Causes curve to shift to right
–> lower affinity - O2 readily dissociates into tissues (muscles) for aerobic exercise

41
Q

How does carbon monoxide (CO) affect O2 transport?

A

-Will bind to haemoglobin much more readily than O2 –> Hb has higher affinity for CO than O2
-Competitive inhibition - CO blocks O2 binding to haem groups on haemoglobin
-When CO bound to Hb = carboxyhaemoglobin
-Curve shifts left = higher affinity (binds more readily but not dissociate readily) - no O2 delivered to tissues = hypoxia & even death

42
Q

CO2 transported in blood vs O2?

A

-Transported more readily than O2
—> as CO2 = more soluble in plasma

43
Q

Amounts of CO2 in arteries & veins?

A

–In blood = ml CO2 100ml blood)
-Arterial blood (= CaCO2) – 48% vol
– Venous blood (CvCO2) – 52% vol

44
Q

How does CO2 get transported in arterial blood?

A

-Physically dissolved in plasma (5%)
-Physically dissolved/converted to bicarbonate ion (90%) —> MOST
-Combined with Hb 23% = carbaminohaemoglobin

45
Q

What does CO2 bind to in haemoglobin to form carboxyhaemoglobin?

A

-Globin portion of the haemoglobin molecule -Carbamohaemoglobin
-Forms where is high PCO2

46
Q

Is the combination of CO2 with haemoglobin reversible or irreversible?

A

Reversible - as carboxyhaemoglobin will reform haemoglobin in lungs (CO2 dissociates) to then form oxyhaemoglobin

47
Q

Reaction to show how CO2 decreases pH of blood?

A

H2CO3 can exchange w/ Cl- at cell memb

48
Q

What is the enzyme that converts CO2 and H2O to form H2CO3?

A

Carbonic anhydrase

49
Q

What is the reaction to show the conversion between oxyhemoglobin & deoxyhaemoglobin?

A
50
Q

Summarise the factors that affect O2 saturation of haemoglobin?

A

-PO2
-pH
-Temp
-BPG
-PCO2

51
Q

What is the Haldane effect?

A

O2 loading facilitates CO2 unloading from Haemoglobin
= Increased capacity of blood to carry CO2 under conditions of decreased haemoglobin saturation
-Ability of deoxygenated Hb to carry more CO2 than in oxygenated state

Physiology (10 decks)

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