Lecture 19: Gas Exchange and Respiratory Control Flashcards
Oxygen is carried in the blood in what two forms?
- dissolved O2 in the plasma
- bound to haemoglobin in red blood cells
Why is only a small amount of O2 dissolved in plasma?
Because O2 does not dissolve well, especially in the warmth
Briefly describe the cooperatively of haemoglobin
The most difficult oxygen to bind is the first one; the more O2 binds, the more tightly all the others bind
What is the benefit of having a sigmoidal curve to describe the affinity of haemoglobin for O2?
It means that less O2 can be released to tissues that do not need it and more can be released to tissues do need it
How does pH affect O2 affinity?
lower pH means a reduced O2 affinity which means more O2 can be dropped off at the tissue
How does the temperature affect O2 affinity?
higher temperature means reduced O2 affinity which means more can be dropped off at the tissue
Why is the oxygen binding curve a sigmoidal shape?
Because at low O2 pressure, few haem are occupied so the binding is slow
As O2 begin to bind, the affinity increases so the others bind a lot faster and stronger
The curve slows and plateaus because as more O2 bind, there are less binding sites so the remaining O2 take a while to find the empty sites
During exercise, why is it helpful that skeletal muscles produce lactic acid and heat during exercise?
Because the decrease in pH and increase in heat reduce O2 affinity which means that less O2 binds and more O2 is released into the tissue
What are the three forms that CO2 is transported in?
- dissolved in plasma
- bound to haemoglobin
- converted to bicarbonate
Of the CO2 that is bound to haemoglobin, some of it is bound as carbaminohaemoglobin and the rest is converted to _________ _________ by _______ ________
carbonic acid
carbonic anhydrase
The carbonic acid dissociates into
H+ and bicarbonate ion
The production of H+ by the dissociation of carbonic acid means
the pH is lowered
Describe the system to control breathing
sensors send afferent information regarding gas levels to the central controller in the pons, medulla and other parts of the brain, then efferent signal is sent from the brain to the effectors to administer the change
What are respiratory sensors?
- chemoreceptors
- baroreceptors
- lung stretch receptors
- protective reflexes
What do chemoreceptors control?
CO2 levels
Describe the process the decrease CO2 levels after an increase?
- the chemoreceptors sense the increase
- they activate the effectors (respiratory muscles)
- this increases respiratory rate with increased elimination of CO2 at alveoli
- this decreases the arterial CO2 pressure
Describe how the baroreceptors affect respiratory function by using arterial BP going down as an example
- Arterial BP decreases which reduces the flow
- this is sensed by the baroreceptors
- they increase the respiratory minute volume
- this increases the uptake of air
Describe the role of the lung stretch receptors
- as the lungs inflate or deflate, they send afferent input from stretch receptors
- the brain then send efferent output preventing them stretching too far either way
What are the protective reflexes?
they detect irritation and the brain responds by sending efferent signal that triggers a sneeze or a cough
