Week 4 Oxygen in blood Flashcards
Describe heamoglobin in a tense state?
Low affinity for oxygen making it difficult for oxygen to bind
Describe heamoglobin in the relaxed state?
High affinity for oxygen making it easier for oxygen to bind
When pO2 is low what state will Hb be in?
Tense state so harder to pick O2 up
At what pO2 is Hb usually fully saturated?
10kPa
At what pO2 is Hb usually half saturated and at what pO2 is Hb vertically not saturated at all?
Half- 3.5-4kPa
0-
What is the usual pO2 in the alveoli?
13.3kPa so Hb fully saturated
What is the normal Hb conc in arterial blood and how is this used to calculate oxygen content in arterial blood?
2.2mmol.L-1 Hb in arterial blood
Each Hb can bind 4molecules of O2
4x2.2=8.8mmol.L-1
What is the usual pO2 in tissues?
5kPa
If Hb saturation drops to around 65% in the tissues how much O2 is given up?
Given up 35% so 8.8x0.35= 3mmol.L-1
What is the normal and maximum cardiac output?
Normal- 5L.min-1
Max- 25L.min-1
what is the minimum pO2 that a tissue can have before diffusion stops and how does capillary density affect this?
lower than 3kPa
the higher the capillary density the lower the pO2 can go as the diffusion distance is less
- in metabolically active tissues there will be a much higher capillary density such as in the heart
what is the boar affect, what causes it and what does this mean for Hb?
shifts dissociation curve to the right meaning at a given partial pressure the Hb will be less saturated and therefore will have given more up but is in the T state so picks up less readily ensuring O2 stays in the tissues
caused by increases in temp, falls in pH and increases in 2-3 BPG
what is the pH and temp like in metabolically active tissues and what affect des this have on Hb?
more acidic as producing H due to exercise therefore boar effect results in a shift of curve to the R and more O2 is given up
also increase in temp due to increased metabolism having the same affect
what is the maximum unloading of O2 and where and when does this occur?
in tissues where pO2 can fall very low and in metabolically active tissues where it is more acidic and a higher temp- results in about 70% bound oxygen being given up
how much O2 is usually given up over the whole body from arterial blood?
27% meaning there is a large reserve
what affect does carbon monoxide have on Hb?
reacts with Hb creating COHb,
binding of CO makes the unaffected subunits have a much higher affinity for O2 meaning they pick it up easier but will not give up O2 at the tissues
this is fatal if COHb is >50%
what is cyanosis and what is it caused by?
bluish colouration due to unsaturated Hb- deoxygenated Hb less red than oxygenated
- can be peripheral-hands and feet- due to poor local circulation, or
- central- tongue, lips- due to poorly saturated blood in systemic circulation
what does a pulse oxometer do and what is its downfall?
measures the level of Hb saturation by detecting differences in absorption of light between oxygenated and deoxygenated Hb
DOES NOT SAY HOW MUCH HB PRESENT
