respiration 2 Flashcards
whats Dalton’s Law
-The total pressure of a mixture of gases is the sum of their individual partial pressure
Transport of gases around body: dry - atmospheric
-Gas, Fraction(%), Partial Pressure (mmHg)
N2. 78.09 593.48
O2 20.95 159.22
CO2 0.03 0.23
Ar 0.93 7.07
H2O 0 0
Transport of gases around body: Wet – Trachea
-Gas, Fraction (%), Partial Pressure (mmHg)
N2 73.26 556.78
O2 19.65 149.22
CO2 0.03 0.21
Ar 0.87 6.63
H2O 6.18 47
whats Gases in Solution like
-For Oxygen
[O2]dis = s x PO2
-Where
s is 0.0013 mM/mmHg
-In arterial blood – PO2 is approx 100mmHg
So [O2]dis = 0.13mM
-In mixed venous blood PO2 is approx 40mmHg
So [O2]dis = 0.05mM
how is Oxygen Transport by the Blood
-Oxygen has a relatively low solubility in saline
-0.003 ml O2 per 100mls of blood per mmHg
-So under conditions where partial pressure of O2 is 100mmHg, the plasma can carry -0.3ml O2 per 100mls.
-At rest with a Cardiac Output of approx 5000mls/min the plasma can provide at most-15ml O2/min.
-However the body requires 250ml O2/min
-Clearly the plasma cannot deliver enough oxygen alone. —Overcome by the presence of red blood cells containing Haemoglobin.
Haemoglobin structure
-Haemoglobin has a tetrameric structure with four subunit coming together to give a final molecule with a molecular weight of 68kD
-Each unit consists of a Haem unit and a globin chain.
-Depending on Hb type there are different combinations of globin chains.
-In Adult Hb there are 2α chains and 2β chains.
haem group in hB
-The Haem unit is a porphyrin ring containing a single iron atom.
-For oxygen to bind the iron has to be in the Fe2+ state- The enzyme methaemoglobin reductase helps convert any Fe3+ back to Fe2+.
-Haemoglobin exists in two states, tense and relaxed: In tense state low affinity for O2, In relaxed state high affinity for O2
Implications of shifts in the Oxygen-Haemoglobin dissociation curves
-In tissues undergoing active respiration :
=Increased temperature
=Increased CO2 production
=Decrease in pH
-All these factors cause a right shift in the dissociation curve:
-Upshot is decreased affinity for O2 on Haemoglobin – more O2 released to the tissue
whats the Fetal -Haemoglobin like
-In Fetal-Hb the β-globin chains are replaced by γ-chains. There is a leftwards shift in Hb-O2 curve – higher affinity for O2
whats Carbon Dioxide Transport by the Blood
-The Blood carries CO2 as :Dissolved carbon dioxide, Carbonic acid, Bicarbonate, Carbonate and Carbamino compounds
what are the two categories of lung disease
-Obstructive: Reduction in flow through airways
-Restrictive: Reduction in lung expansion
-Both reduce ventilation
whats the Flow-Volume Relationships
-residual volume- all air breathed out
-breathing out as much as you can and then breathing in as much as you can
whats Obstructive Lung Disease
-The result of a narrowing of the airways- change in diameter- increased resistance and reduction of flow
-Narrowing could be due to:
=Excess secretions
=Bronchoconstriction – Asthma
=Inflammation
-In all cases there is an increased resistance to the flow of air.
how can you tell if someone has obstructive lung disease with spirometry
-FEV1 < 80% of FVC
-decrease in FEV1
-ratio needs to be over 80% to be
-volume-time curves: In many cases FVC is unaltered but there is the decrease in FEV1
-flow-volume loops: The initial flow and peak flow can be similar to normal but there is a sharp fall in flow-rate giving a concave shape to the curve.
examples of obstructive diseases
-Chronic Bronchitis Persistent productive cough and excessive mucus secretion (three consecutive months in last two years)
-Asthma - inflammatory disease
-Chronic obstructive pulmonary disease (COPD) - structural changes
-Emphysema –loss of elastin
asthma
-The sufferer has hyper-active airways.
-Trigger can be either: Atopic (extrinsic) – allergies, contact with inhaled allergens., or Non-Atopic (intrinsic) – Respiratory infections, cold air, stress, exercise, inhaled irritants, drugs.
-Response: Movement of inflammatory cells into the airways, release of inflammatory mediators such as histamine and subsequent bronchoconstriction.
whats the Asthma treatment
-Treatment tend to rapid short acting or longer term.
-Short-acting β2-adrenoreceptor agonists – salbutamol- Causes dilation of airways.
-Longer acting treatments: Inhaled steroids. Glucocorticoids such as beclometasone, act to reduce the inflammatory responses, Long acting β-adrenoreceptor agonists
whats restrictive lung diseases
-Reduced chest expansion:Chest wall abnormalities, Muscle contraction deficiencies
-Loss of compliance (fibrosis): Normal aging process, Increase in collagen, Exposure to environmental factors
how can you tell if someone has restrictive lung disease with spirometry
-decreased VC
-volume-time curves:Reduction in FVC, but FEV1% can remain unaltered or even increase
-flow-volume loops: The shape of the relationship tends to be normal but there is a reduction in the volumes of air moved. Also there can be a reduction in the peak flow.
whats Asbestosis
-Slow build-up of fibrous tissue leading to a loss of compliance.
-example of restrictive lung disease
whats Central Control of Respiration
-Breathing – automatic, rhythmical process. The basic respiratory rhythm is generated by centres in the medulla.
-Inputs from various regions act to modify the respiratory pattern
-Essentially breathing is an involuntary mechanism but it can be altered consciously
-Hyperventilation
-Breath Holding
-However these are temporary controls and will be overridden if required by place in medulla which is responsible for basic breathing pattern
what are the different types of Medullary centres
-Dorsal Respiratory Group (DRG): Controls Inspiration by sending signals to the inspiratory muscles, Spontaneously active – shows period of activity – shuts off – period of activity
-Ventral Respiratory Group (VRG): Controls Inspiration and expiration, Inactive during quiet respiration, During activation helps control forceful inspiration and expiration
what are pons
-Two centres in the Pons sends stimuli to the medulla to regulating rate and depth of breathing
-pneumotaxic centre increases the rate by shortening inspirations.
-inhibitory effect on inspiratory centre
-apneustic centre - increases the depth and reduces the rate by prolonging inspirations.
-stimulates inspiratory centre
negative feedback mechanism of stretch receptors : hearing-breuer reflex
-phrenic nerve-> diaphragm contracts causing lung to inflate-> stretch receptor in lungs sending signals to brain via vagus nerve-> inspiratory centre
chemoreceptors
-Central Chemoreceptors – Monitor conditions in the cerbro-spinal fluid. Sensing carbon dioxide and pH- Indirect response to a rise in CO2 - stimulation leads to an increase in ventilation.
-Peripheral Chemoreceptors – Located in the carotid body and aortic arch- Respond to
=Increase in CO2
=Decrease in pH
=Decrease in O2
-Stimulation leads to an increase in ventilation.
