Normal Physiology Flashcards
What percentage of O2 bound to Hb is used in one pass of the bodies systems
25%
An increase in [H+] causes what shift in the oxygen dissociation curve?
Right
How can low oxygenation of the blood be compensated for?
Greater amounts of Hb
Greater CO
How much CO2 does the body produce at BMR compared to while exercising?
At BMR: 200ml/min During exercise: >4000ml/min
What does PaO2 stand for?
Partial pressure of arterial O2
Why do small airways contribute low resistance?
Because there are a lot of them
What does central cyanosis reflect in the blood?
Arterial blood is not well oxygenated
How much O2 does the body use at BMR compared to while exercising?
At basal metabolic rate: 250ml/min During exercise: >4000ml/min
What is the function of carbonic anhydrase?
It catalyses the reaction of CO2 + H2O > H2CO3
An increase in PCO2 causes what shift in the oxygen dissociation curve?
Right
What are the main functions of the lungs?
- Oxygenate pulmonary arterial blood 2. Removed CO2 from pulmonary arterial blood 3. Maintain acid-base balance
What do central chemoreceptors respond to? Where are they located?
H+ Ventrolateral medullary surface
Why is diffusion of CO2 20x greater than O2 given that the driving pressure is greater for O2?
CO2 is more soluble
What does PiO2 stand for?
Partial pressure of inspired O2
What does PA02 stand for?
Partial pressure of alveolar O2
An elevated PaCO2 is generally due to a ventilation or diffusion problem? Why?
Ventilation, because CO2 diffusion is very fast.
How many branches are there of the lung airways?
23
What drives O2 to bind to Hb?
Its concentration dissolved in plasma (PaO2 or PvO2)
Apart from central and peripheral chemoreceptors, what factors effect respiration?
Stretch receptors in the chest wall
Muscle and joint receptor
Cortical control
What are the main muscles of expiration?
Internal intercostals
Abdominals
What are implications of a right shift in the oxygen dissociation curve during exercise?
O2 is more easily unloaded
An increase in temperature causes what shift in the oxygen dissociation curve?
Right
What type is air flow is seen in the small and large airways?
Laminar and turbulent respectively
Which way will the oxygen dissociation curve shift if Hb’s affinity for O2 is increased?
Left
What is the vital capacity?
The difference between total lung capacity and residual volume
T/F Carbon monoxide has a greater affinity for Hb than O2
True, 240x greater
What is the normal PaO2, PaCO2 and pH of arterial blood?
O2 - 100mmHg
CO2 - 40 mmHg
pH - 7.4
What percentage of CO2 is bound to Hb for transportation?
30%
What do peripheral chemoreceptor respond to? Where are they located?
H+, CO2, O2 Carotid and aortic bodies
What nerves are important in stimulating inspiration?
Phrenic (diaphragm)
Intercostal nerves (external intercostal muscle)
What two factors contribute to the work of breathing?
Resistive - Overcoming airflow resistance
Elastic - Pushing against elastic lungs (imagine blowing up a balloon) and expanding the chest wall
What percentage of CO2 is dissolved in plasma?
10%
True or false, in healthy individuals undergoing exercise, there is not enough time for Hb to be completely oxygenated in alveolar capillaries.
False, the time required is 0.25s which is the time spent by blood in the capillaries during exercise.
What is the difference between residual volume and functional residual volume?
Residual volume is what is left after maximal expiration (1,200ml) while function residual volume is what is left after normal expiration (2,200ml)
What does a low V/Q match indicate?
Ventilation doesn’t match perfusion
What are main muscles of inspiration?
Diaphragm
External intercostals
Sternocleidomastoids
Why are more CO2 bound in the carboamino form in venous blood cf to arterial?
Because there is more reduced Hb (Hb without O2, H+ instead) with has a higher affinity for CO2 than HbO2
What percentage of vital capacity is used at maximum exercise?
50%
In what form is the majority of CO2 transported?
Bicarbonate: 60%
