Respiration 3+4 Flashcards
What is the shape of a flow-volume loop?
Exhalation- curve increases rapidly Reaches peak expiratory flow Slowly decreases Decrease is effort independant Inhalation is negative
What is the shape of a volume-time curve?
Most air expired at the start (rapid rise)
About 80% expired in the first 1
Curve extends horizontally (no more air can be expired)
What is FEV1%?
FEV1/VC
What is it a sign of if the FEV1% decreases below 80%
Obstructive lung disease
What is obstructive lung disease?
Narrowing of the airways causing a restriction of flow
What are 4 types of obstructive lung disease?
Chronic bronchitis - persistant cough and excess mucus (3 consecutive months in 2 years)
Asthma - Hypersensitivity of the bronchial smooth muscle
COPD - swelling in the LOWER airways
Emphysema - loss of elasticity in alveoli
Change in spirometry in obstructive lung disease?
VC is normal
FEV1 is less than 80%
Flow-volume:
Sharper decrease but similar initial raise
Volume-time:
Endpoint volume is the same
What is the atopic causes of asthma and what does this cause?
Allergies
Increases IgE
Increases inflammation
What are the non-atopic causes of asthma?
Respiratory infections Cold air Stress Exercise Ibuprofen
NO IgE increase involved
What is the response to triggers of asthma?
Inflammatory cells move into the airways
Release of inflammatory mediators (histamine)
BRONCHOCONSTRICTION
How does salbutamol treat asthma?
SHORT-ACTING B2 adrenoreceptor agonist
Acts through Gs pathway
Blue inhaler
How does glucocorticoids treat asthma?
LONG-ACTING B2 adrenoreceptor agonist
Brown inhaler
What are the 2 causes of restrictive lung disease?
1) Loss of compliance (fibrosis - increase in collagen)
2) Reduced chest expansion due to chest wall abnormalities or muscle contraction deficiency
What is vital capacity based upon?
Age, height, gender, weight
What happens to the spirometry in restrictive lung disease?
Flow-volume
Shape is normal
Reduction in volume (look smaller)
MAY be decrease in peak flow
Volume-time
VC decreases
FEV1% remains unaltered or even increase
Where is the basic rhythm generated and where is the pattern of breathing modified?
Generated in the medulla
Modified in the pons
If cut above medulla what happens to breathing?
If cut below medulla what happens?
BASIC rhythm maintained
Breathing is ceased
What are the two centres in the medulla which lead to relaxation and contraction of the brochi muscles and how?
1) Dorsal respiratory group
- Basic INSPIRATION pattern (not expiration)
- Sends signals to inspiratory muscles
- Spontaneously active
- Periods of activity during INSPIRATION
- Increase in firing
- Contraction
- Shut down signalling when expire
2) Ventral respiratory group
- Linked to FORCED inspiration and expiration
- Inactive during quiet inspiration
- (Hering-Breur reflex) - negative feedback loop
- Stretch receptors in the lung send signals back to the medulla via the Vagus nerve
- INHIBITS respiratory system
What two centres in the pons adjust respiratory patterning?
1) Pneuomtaxic centre
- INHIBITORY EFFECT on INSPIRATORY centre
- increases respiration RATE by REDUCING FIRING
- Shorter inspirations
2) Apneustic centre
- STIMULATES inspiratory centre
- Increases respiration DEPTH by INCREASING FIRING
- Prolonging inspirations
What do central chemoreceptors do?
Monitor conditions of the CSF
Sense changes in pH and CO2
What do the peripheral chemoreceptors respond to and where are they located?
Located in the carotid sinus and aortic arch
Respond to pH and CO2 and decrease O2
What 5 things is CO2 carried as in the blood?
Dissolved CO2 gas Carbonic acid Bicarbonate acid Carbonate Carbamino compounds
What are the fates of CO2 in the capillary?
Dissolved in plasma by binding to carbamino compounds or as bicarbonate
- Most enters the RBC by the ‘Rhesus pathway’ or by the ‘protein pathway’
What are the fates of CO2 in the RBC?
- Dissolves into cytoplasm
- Combines with Hb but not at the Fe binding site
- Majority is converted into H+ and HCO3- by CARBONIC ANHYDRASE 2
- In respiring tissues HCO3- goes out of the RBC via band3 and Cl- comes in
What causes O2 to dissociate from the RBC?
Local acidification due to CO2
Difference between lung ventilation at the apex and the base of the lungs?
Apex:
- Larger starting volume of alveoli
- Gas exchange greater
Base:
- Smaller starting volume of alveoli
- Higher ventilation (more room for expansion)
- Greater lung perfusion
What is lung perfusion?
The passage of fluid from the circulatory system to the organ
Linked to posture and gravity
What is the Ventillation/perfusion ratio?
Ventilation/Perfusion
Use to get an idea of gas exchange
If miss-matched it can highlight a problem with ventilation or circulation
What is Dalton’s law?
The total pressure of a MIXTURE of gases is the SUM of all of their individual pressures
- Adding water to air (in the lungs) increases the partial pressure of water and decreases the pp of the other gases
- But overall the total pressure remains the same
What is Henry’s law and what does it calculate?
Calculate the amount of gas dissolved in solution using partial pressures
[gas]dis = s x Pgas
s is the solubility coefficient which changes with gases
What is the structure of heamoglobin?
- Tetramer
- Each subunit has: Heam unit and globin chain
- Globin chains differ depending upon Hb type.
Structure of the Haem unit in Hb?
Porphorin ring- containing a single Fe2+ (must be +2 to bind)
2 states of haemoglobin?
What causes the switch from the two states?
Tense- low affinity for O2
Relaxed - high affinity for O2
Binding of one O2 to one heam group switches all four subunits to the relaxed state
What happens to the O2 carrying capacity of haemoglobin when the dissociation curve shifts to the:
Right?
Left?
To the right: carry LESS oxygen (more dissociation)
To the left: carry MORE oxygen (less dissociation)
What causes the dissociation curve to shift to the right?
Increase pp Co2
Increase of temperature
Increase in 2,3-diphosphoglycerate
Decrease in pH
What does 2,3-diphosphoglycerate do to Hb?
Binds to B chain. Binds better in a deoxygenated state
How is the structure of Hb different in the fetal to in the adult?
Adult:
2 alpha chains
2 beta chains
Fetal:
Left shifted (higher afinity for )2)
2 beta chains replaced gamma chains
Lose affinity for 2,3-diphosphoglycerate
