k1. Respiratory System

7/30/2019 k1. Respiratory System

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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

k1. Respiratory System

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