Lect29 - Feb18 - resp IV and renal I - O2 diuses down a PP...

Topic #2 Respiration 26
Some Questions on the Oxyhemoglobin Dissociation Curve
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60 70 80 90 100110120130
Po2 Torr
O2 Content ml O2/100 ml Blood
Decrease O2 content by 2 ml.
Decrease O2
Content by 2 ml.
What are the contributions of
dissolved & Hb bound sources of
oxygen when content decreases
from 20 to 18 ml?
Why is the change in partial
pressure for oxygen so much
greater with a decrease in content
from 20 to 18 compared to 14 to 12
ml?
What are the contributions of
dissolved & Hb bound sources of
oxygen when content decreases
from 14 to 12 ml?
O2 di f٠ uses down a PP gradient. The PP gradient determines how much di f٠ uses. As O2 di f٠ uses from it's dissolved state into the tissues, the PO2
of the blood decreases, thus decreasing the PP gradient for di f٠ usion. The decrease in PO2 is bu f٠ ered by Hb. As the PO2 falls, Hb releases O2,
but Hb releases O2 at di f٠ erent rates depending on the PO2 of the blood = Hb's a ff٠ nity for O2 changes depending on the PO2 of the blood. The
more readily Hb releases O2, the slower the fall in PO2. The time it takes for blood to flow though the capillaries is on the order of 1/2 second, so
di f٠ usion must happen very quickly.
1) there is a 2ml decrease in O2 content from 20ml to 18ml --> PO2 falls from 100 to 60 Torr. As O2 di f٠ uses from the dissolved state out into
the tissues, the amount of O2 dissolved decreases --> Hb bu f٠ ers the drop in PO2 very little because it's a ff٠ nity for O2 is still very high. 2) there
is a 2ml decrease in O2 content from 14ml to 12ml --> PO2 falls from 38 to 33 Torr. Only a 5 Torr di f٠ erence. Hb's a ff٠ nity for O2 is much less at
this PO2, so it more readily gives up O2. the amount dissolved is much less. As O2 leaves the blood, the PO2 < 60 Torr, Hb gives up O2 and this
bu f٠ eres the decrease - slows the fall in dissolved O2 and thus slows the fall in PO2. ENHANCES DIFFUSION OF O2 INTO THE TISSUES.
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Topic #2 Respiration 27
Model Showing Hemoglobin’s Buffering of Dissolved Oxygen and the Partial
Pressure of Oxygen as Oxygen Content Decreases

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Respiration 21
Outline Topic #3
1. Chemical Control of Ventilation – Peripheral and Central Chemoreceptors.
2. Central Neural Control of Ventilation – Medullary, Midbrain, & Cortical Control. Hering-
Breuer (Inspiratoinhibitory) Reflex
You are responsible
for covering this
material on your own.

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Topic #3 Respiration 29
Chemical and Central Neural Control of Respiration
Fig. 13-33 & 13-34
Chemical Control
1. Peripheral Chemoreceptors – Carotid Bodies
& Aortic Bodies
2. Central Chemoreceptors – Two populations in
Brainstem
• Adjacent to the 4 th Ventricle &
influenced by BBB
• Population neurons in Brainstem
adjacent to permeable capillaries
( permeable gases and ions )
3. Effective Stimulus at chemosensitive cells
• Po2
• H+
Central Neural Control – Brain Stem + Higher Areas
• Generation of Basic Breathing Rhythm in
Medullary Respiratory and Expiratory Neuron
Groups.