Flashcards in Option D.6 Transport and Respiratory Gases (AHL) Deck (39)
What is the pressure of a gaseous mixture equivalent to?
sum of pressure of the component gases
What is the pressure of a specific gas in a mixture called?
What is partial pressure defined as?
fraction of total gas pressure exerted by particular gas
What is a hemeoglobin composed of
interlocking subunits like:
- globular proteins
- non protein heme group
What is measured on an oxygen dissociation curve?
affinity of haemoglobin for oxygen (measured through percentage saturation with oxygen)
Why is the oxygen dissociation curve s-shaped?
- first oxygen molecule attaches with difficulty
- second combines easy
all becomes saturated
Why does an oxygen dissociating curve S-line showed me?
the amount of oxygen held by hemeoglobin depend on partial pressure of oxygen
How does partial pressure affect our lungs?
- air saturated; partial pressure of component gases is different from outside
What is the effect of CO2 on oxygen transport?
- increased CO2 shifts oxygen curve to right
- oxygen released more easily
- useful for tissues
Give another example (except from indo) of a reverse of oxygen
- found in skeleton muscles
- reserve/store used during intense muscle contraction
- higher affinity for oxygen (not hemoglobin)
- acts as oxygen store
What happens when oxygen concentration in muscle falls?
oxymyglobin dissociates to supply oxygen;
allows aerobic respiration;
if reserve is used up by extended muscle contraction;
How does a fetus obtain oxygen?
mother's blood through placenta;
maternal and fetus characteristics are not similar, they do not touch;
Do fetal and maternal blood circulation ever mix?
No. come very close but never mix
Why do fetal and maternal blood circulation never mix?
Hemoglobins are different. Fetal hemoglobin combines with oxygen more readily at same partial pressure
How can CO2 be transported in blood plasma?
- dissolved as CO2
- reversibly converted to biocarbonate ions that are dissolved; by red blood cell enzyme carbonic anhydrase
- bound to plasma proteins
What property does blood have to keep it from being acidic?
hydrogen ions are buffered by plasma proteins and hemoglobins
How is CO2 converted into hydrogen carbonate ions?
red blood cells and catalysed by carbonic anhydrase (enzyme); lowers pH of blood
When is the reaction of CO2 conversion to HCO3 used?
in tissues, CO2 is generated; so need to be trnasported to lungs via dissolving as HCO3;
When is the conversion of HCO3 into CO2 used?
In lungs, CO2 needs to leave blood; CO2 is stored as HCO3 in blood and must be converted
What controls the rate of our ventilation?
respiratory control centre in medulla oblongata; two nerve cells bring about ventilation movement by reflexive action; involuntary action
What are the two sets of nerves in our medulla oblongata?
intercostal nerves: rate and depth of breathing;
expiratory nerves: inhibit inspiratory centre, stimulate expiration
Outline how breathing is controlled in body?
- intercostal nerves stimulate intercostal muscles of the thorax;
- phrenic nerves stimulate diaphragm;
- lungs expand, stretch receptors in chest and lung send signal to respiratory centre
- triggers cessation leading to inspiration until exhalation;
- new signal
What is the main stimulus that affects breathing?
concentration of blood carbon dioxide (drop in blood pH);
What detects changes in blood pH?
chemoreceptors are sensitive to pH changes and concentration of blood CO2
What occurs when blood pH is low?
chemoreceptors in artery/aorta detet this;
send message to medulla oblongata (centre);
medulla sends imulse to diaphragm and intercostal muscles;
ventilation rate increased
more gas exchange
Why is regulation of blood pH important?
pH of blood must stay within NARROW range of 7.35 to 7.45
How does blood regulate pH so narrowly?
has buffers that help keep blood resistant to small changes of pH, include HCO3 and amino acids/proteins
What ways can blood over come pH changes quickly?
Hyperventilation (removed CO2);
in kidney H+ secreted into urine bound;
tubules reabsorb HCO3 to neutralize;
HCO3 secreted into distal convulated tubule of kidney
buffers cannot remove acid/base, but minimize effect
What are 3 major components of cigarettes?
Carcinogen, Nicotine and carbon monoxide