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BBS1002 > CASE 5 > Flashcards

CASE 5 Flashcards

1
Q

Hemoglobin

A
  • globular heme protein
  • heme binds oxygen and carbon dioxide
  • gives red blood cells their color
  • has 4 heme groups which surround globon group
  • when bound to oxygen it is called oxyhemoglobin
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2
Q

Hb binding to O2

A

(H)Hb + O2 –> HbO2 (+ H+) (the H+ is coming from the carbonate buffer; oxygen swaps
places

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3
Q

law of mass action

A
  • concentration of free O2 increases –> more O2 binds to Hb and equation shifts to right
  • in pulmonary capillaries, oxygen from alveoli diffuses into RBC where it can bind to Hb until it reaches equilibrium
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4
Q

releasing O2 in tissue

A
  • PO2 of cells determines how much oxygen is unloaded from Hb.
  • cells increase metabolic activity –> PO2 decreases –> Hb releases more oxygen
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5
Q

binding of O2 to Hb

A
  • first one binds difficult, after the first one, the protein changes shape and it is easier for the rest.
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6
Q

amount of O2 that binds to Hb

A

depends on 2 factors:

  1. the PO2 in the plasma surrounding the RBC’s
  2. the number of potential Hb binding sites available in RBC’s
    - Plasma Po2 is primary factor determining what % of the available binding sites are occupied by oxygen, known as percent saturation of Hb.
    - when PO2 decreases –> less oxygen is bound to Hb and transported
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7
Q

establishment PO2

A
  1. the composition of inspired air
  2. the alveolar ventilation rate
  3. the efficiency of gas exchange from alveoli to blood
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8
Q

mean corpuscular hemoglobin

A
  • total number of oxygen-binding sites depends on number of Hb molecules in RBC’s.
  • can be estimated by counting the RBC’s and quantifying the amount of Hb.
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9
Q

percent saturation of Hb

A

amount of oxygen bound to Hb at any given PO2:

(amount of O2 bound / maximum that could be bound) x 100

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10
Q

Oxyhemoglobin saturation curves

A
  • reflects Hb and its affinity for oxygen.;
  • normal alveolar and arterial PO2 (100 mmHg), 98% of Hb is bound to O2.
  • as the PO2 stays above 60 mmHG, Hb is more than 90% saturated and is fine
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11
Q

Physiological significance shape of curve

A
  • average value venous blood at rest (PO2 = 40 mmHg), Hb is still 75% saturated.
  • remaining oxygen is reserve that cells can draw on in metabolism increase.
  • metabolic activity increases –> more O2 is used –> PO2 drops –> more O2 will release from Hb
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12
Q

Factors that affect oxygen-Hb binding

A

Decrease affinity:
1. higher temperature
2. higher PCO2
shift saturation curve to the right

Increase affinity:
1. lower temperature
2. lower PCO2
shift saturation curve to the left.

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13
Q

Bohr effect

A

a shift in the saturation curve caused by a change in pH

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14
Q

2,3-diphosphateglycerate (2,3-DPG)

A
  • compound in glycolysis pathway
  • affects oxygen-Hb binding
  • extended periods of low oxygen triggers an increase in 2,3DPG production in RBC’s -> lowers affinity of Hb -> shifts curve to the right
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15
Q

pH effect on affinity

A

low pH –> more CO2 –> more CO2 binds to Hb –> Hb less affinity to oxygen because some space is occupied

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16
Q

hypercapnia

A
  • elevated pCO2
  • it is important that CO2 is removed from the body because hypercapnia causes pH disturbance –> acidosis.
  • can also depress CNS function
17
Q

CO2 and bicarbonate ions

A

conversion of CO2 to HCO3- has purpose:

  1. can transport more CO2 from cells to lungs
  2. HCO3- can act as a buffer and helps stabilize the body’s pH
18
Q

Carbonate buffer

A
  • CO2 + H2O –> H2CO3 –> H+ + HCO3-
  • continues until equilibrium
  • to keep the reaction going end products must be removed from cytoplasm of RBC
19
Q

Two mechanisms to remove free H+ and HCO3-

A
  1. chloride shift

2. respiratory acidosis

20
Q

Chloride shift

A
  • exchanges HCO3- for Cl-
  • makes the cell electrical neutral
  • bicarbonate is an extracellular buffer
21
Q

Respiratory acidosis

A
  • removes free H+ from RBC cytoplasm.
  • Hb in RBC acts as a buffer and binds H+ + Hb –> HbH
  • prevents large changes in body pH
  • if PCO2 is elevated much above normal, the buffer does not work. H+ accumulates in plasma
22
Q

Acidosis/alkalosis

A

Metabolic: respiratory system will help maintain homeostasis:

  • Alkalosis: vomiting a lot, HCL out of body
  • Acidosis: renal system does not remove a lot of acid

Respiratory: the metabolic system will help maintain homeostasis:

  • alkalosis: high breath rate
  • acidosis: low breath rate
23
Q

Co2 removal at lungs

A
  • PCO2 of alveoli is lower than that of venous blood in pulmonary capillaries –> Co2 diffuses into alveoli –> plasma PCO2 begins to fall
  • allows dissolved CO2 to diffuse out of RBC’s
  • removal of CO2 causes the H+ to leave Hb
24
Q

hyperpnea, increase of breathing depth and rate

A
  • more altitude is thinner air = less oxygen/L
  • lower Po2 meand lower saturation of Hb –> sensed in carotid bodies, which cause hyperpnea
  • inhibits the respiratory center from enhancing the respiratory rate as much as would be required
25
Q

High altitude

A
  • heart beats faster –> stroke volume is decreased (because afterload goes up)
26
Q

full acclimatization high altitude

A
  • renal excretion of bicarbonate –> adequate respiration to provide oxygen
27
Q

acclimatization leads to:

A
  1. increased pulmonary ventilation
  2. increase of RBC’s
  3. increased diffusing capacity
  4. increased tissue capillarity
  5. cellular acclimatization; cells become more efficient in using oxygen
28
Q

full adaptation to high altitude

A
  • is reached when the increase of RBC’s stopt

- EPO, secreted by kidney in response to cellular hypoxia: stimulates red blood cell production in bone marrow

29
Q

Medullary inspiratory center

A
  • generates rythmic action potentials that stimulate rhythmic contraction of muscles
30
Q

pneumotaxic area

A

stop the lungs from inflating

31
Q

apneustic area

A

prolonging contraction, slows breathing

BBS1002 (10 decks)

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