Post on 14-Apr-2018
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P U L M O N A R Y V E N T I L A T I O N , G A S E X C H A N G E
& C O N T R O L O F R E S P I R A T I O N
D E P A R T M E N T O F P H Y S I O L O G Y
U N S O E D S C H O O L O F M E D I C I N E
RESPIRATORY SYSTEM
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Referensi
Martini, F.H., Nath J.L.. 2009.Fundamentals ofAnatomy & Physiology 8th Ed. USA; PearsonBenjamin Cummings
Tortora, G.J., Derrickson B.. 2006.Principles ofAnatomy & Physiology 11th Ed. USA; John Wiley &Sons
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LEARNING OBJECTIVE
Describe the event that cause inhalation & exhalation
Explain Daltons Law & Henrys Law
Describe the exchange of oxygen & carbondioxide in
internal & external respiration Describe blood gas transportation
Explain how nervous system controls breathing
Explain role of respiratory system on acid-basebalance
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PULMONARY VENTILATION
Respiration has 3 basic steps
Pulmonary ventilation Mechanical procces that moves air in & out of the lung
Inspiration/inhalation
Expiration/exhalation
Pulmonary respiration (external) Gas exchange between alveoli & lung capillary
By diffusion
Tissue respiration (internal) Gas exchange between systemic capillary & tissue
By diffusion
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Inspiration Air flows from atmosphere to alveoli Air pressure inside lung is less than the atmosphere Active procces
Muscle contraction : m. intercostalis external & diafragma
Expiration Air flows from alveoli to atmosphere Air pressure inside lung is higher than the atmosphere Passive procces
Ventilation Alternating pressure difference Boyles Law
Pressure of gas is inversely proportional to its volume
Laplaces Law Pressure in alveoli is directly proportional to surface tension & inversely
proportional to radius of alveoli
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Factors affecting pulmonary ventilation Compliance of the lungs
Abbility to expand 100 x more distensible than balloon Related to the low surface tension & high elasticity Decreased :
Scar lung tissue Pulmonary oedem Increased surface tension Impede lung expansion (paralysis)
Increased : Emphysematous lung
Airway resistance Increased airway resistance disturb air flows Increased :
Mucus production Bronchoconstriction
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Surface tension of alveolar fluid
Force exerted by fluid in alveoli to resist distension
H20 molecules at the surface are attracted to other H20 moleculesby attractive forces
Force is directed inward, raising pressure in alveoliAlveoli has alveolar type II cells which produce phospholipid
(surfactant) that decrease surface tension
Elasticity
Lung is very elastic & ressist of distension
Abbility to return to initial size after distension
High content of elastin protein
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Component Intrapulmonary pressure
Intrapleural pressure
Transpulmonary pressure
Pressure changes Inspiration
Intrapulmonary pressure changes from 0 to -3 mmHg
Intrapleural changes from -4 to -6 mmHg
Transpulmonary pressure = + 3 mmHg
Ekspiration Intrapulmonary pressure changes from -3 to +3 mmHg
Intrapleural changes from -6 to -3 mmHg
Transpulmonary pressure = + 6 mmHg
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GAS EXCHANGE
Passive diffusion as transport mechanism
Daltons Law Each gas in a mixture of gases exerts its own pressure called
partial pressure
Henrys Law
Quantity of gas that will dissolve is proportional to its partialpressure & solubility in water
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Partial pressure
PATM (760 mm Hg) = PN2+ P02 + PC02 + PH20 + Pother gases
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At normal PO2
arterial blood = 100mm Hg
PO2 level in thesystemic veins is = 40mm Hg; PC02 = 46mm Hg
Provides a good index
of lung function
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Rate of blood flow through the pulmonarycirculation = flow rate through the systemiccirculation
Pulmonary resistance is low Autoregulation Pulmonary arterioles constrict when alveolar PO2 decreases
Bronchioles dilate when alveolar PCO2 decrease
Matches ventilation/perfusion ratio
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Ventilation/perfusionrate
Alveoli at apex areunderperfused(overventilated)
Alveoli at the base areunderventilated
(overperfused)
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The rate of gas exchange depends on Partial pressure difference of the gases
Surface area available for gas exchange
Diffusion distance
Alveolar wall Epithelial basement membrane
Capillary basement membran
Capillary endothelium
Molecular weight and solubility of gases O2 has lower molecular weight than C02 (diffusion rate 1,2 x faster) C02 has greater solubility than O2 (diffusion rate 24 x faster)
C02 diffusion occurs 20 more rapidly than O2
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TRANSPORT OF OXYGEN & CARBONDIOXIDE
Hemoglobin as maintransporter RBC has 280 million Hb Hb has 4 polypeptide
chains & 4 hemes
Heme has 1 atom iron thatcombine 1 molecule oxygen Methemoglobin Lacks of electrons & cant
bind oxygen
Carboxyhemoglobin Bind with CO Stronger affinity to CO than
Oxygen (210x)
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Loading depends on PO2 of environment.
Affinity between hemoglobin and 02
Factors affecting affinity pH
DPG
Temperature
PCO2
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Erithrocyte
1,3 bifosfogliserat
bifosfogliserat mutase
2,3 bifosfogliserat
2,3 bifosfogliserat fosfatase
3 fosfogliserat
2,3 bifosfogliserat (DPG) decrease affinity of Hb to O2 that can be used bycell/tissue
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Bohr Effect
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C02 transportation
Dissolved C02 Carbaminohemoglobin
HCO3-
H20 + C02 H2C03 H+ + HC03
-
At the tissues, C02 diffuses into the RBC; shifts thereaction to the right
At the alveoli, C02 diffuses into the alveoli; reaction shiftsto the left
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RESPIRATION CONTROL
Respiratory center DRG
Control diaphragm &external intercostal
Function in every
respiratory cycle VRG
Control accessoryrespiratory muscle
Function only during
forced breathing Interaction of inspiratory
& expiratory neuron
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Apneustic & Pneumotaxic Center Adjust the output of respiratory center
Regulate depth & rate of respiration
Apneustic
Stimulation to DRG
Promotes inspiration by activating I neuron
Respiration become slow & deep
Pneumotaxic
Inhibit apneustic activity Promote active or passive exhalation
Respiration become fast & shallow
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DRG active
Inspiratory muscle contract
Inspiration occur
DRG inactive
Inspiratory muscle relax
Passive expiration occur
DRG active
DRG & I VRG activeE VRG inhibited
Inspiratory muscle contractExpiratory muscle relax
Inspiration occur
E VRG activeDRG & I VRG inhibited
Inspiratory muscle relaxExpiratory muscle contract
Expiration occur
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CHEMORECEPTOR REFLEX
Chemoreceptor Carotid & aortic bodies
Stimulated by decrease inpH or PO2 & indirectly by
PCO2 Ventrolateral surface of
medulla oblongata
Stimulated by decrease inpH & PCO2
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Hypercapnea
Stimulation chemoreceptor
Stimulation DRG
Increased respiratory rate
Increased elimination CO2
Decrease PCO2
Bact to normal
Hypocapnea
Decreased PCO2Inhibition arterial chemoreceptor
Reduced stimulation of CNSchemoreceptor
Reduced stimulation of DRG
Decrease respiratory rate
Decrease elimination PCO2
Increased arterial PCO2 (normal)
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Regulasi pusat pernafasan Regulasi korteks serebri Stimulasi proprioseptor Refleks Hering-Breuer
InflasiDeflasi
Refleks lainnya Stimulasi sistem limbik Suhu
Nyeri Peregangan otot sfinkter ani Iritasi saluran nafas Tekanan darah
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SELAMAT
BELAJAR