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Physiology 12Physiology 12

RespirationRespiration

Germann Ch: 15 &16

Respiratory systemRespiratory system

Functions of the Respiratory SystemFunctions of the Respiratory System

Gas ExchangeGas ExchangeO2 inO2 inCO2 outCO2 out

Other FunctionsOther FunctionspH regulationpH regulationBlood clot removalBlood clot removalSpeech etc.Speech etc.

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External External RespirationRespiration

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Internal Internal RespirationRespiration

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The lungs are surrounded by a The lungs are surrounded by a Pleural sacPleural sac

Parietal Pleura Parietal Pleura Visceral PleuraVisceral PleuraIntrapleuralIntrapleural fluidfluid

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VentilationVentilation

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Ventilation of the lungs is achieved Ventilation of the lungs is achieved by bulk flowby bulk flow

RememberF = ∆P/R

Boyle’s LawBoyle’s LawPP11VV11=P=P22VV22

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Mechanics of Abdominal Mechanics of Abdominal ContractionContraction

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Pressure changes at maximal Pressure changes at maximal inspiration and Expirationinspiration and Expiration

IntrapleuralIntrapleural pressure always remains pressure always remains less than atmospheric to keep lungs less than atmospheric to keep lungs

from collapsingfrom collapsing

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Why don’t the lungs collapse during Why don’t the lungs collapse during inspiration when the alveolar inspiration when the alveolar

pressure is much less than pressure is much less than atmospheric?atmospheric?

PneumothoraxPneumothorax

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Lung Compliance is essential to a Lung Compliance is essential to a healthy respiratory systemhealthy respiratory system

Compliance = ∆volume ÷ ∆ Pressure

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Surfactant: Surfactant: A detergent like substance secreted A detergent like substance secreted

by the Type II alveolar cells that by the Type II alveolar cells that helps maintain lung compliancehelps maintain lung compliance

Lung VolumesLung Volumes

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Minute ventilationMinute ventilation

Tidal volume X respiratory rate

500ml X 10 breathes/minute

= 5000ml of air per minute

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Not all inspired air makes it into Not all inspired air makes it into places where it can contact and places where it can contact and exchange gasses with the blood.exchange gasses with the blood.

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AveolarAveolar ventilationventilation

tidal volume – dead spaceX

Respiratory rate

Control of RespirationControl of Respiration

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Brainstem centers involved in Brainstem centers involved in Respiratory ControlRespiratory Control

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An experimentAn experiment

What if you increased the amount of CO2 in the What if you increased the amount of CO2 in the inspired air?inspired air?

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Carbon Dioxide ReceptorsCarbon Dioxide Receptors(Changes in PCO2 produce changes in pH)(Changes in PCO2 produce changes in pH)

Central Central ChemoreceptorsChemoreceptors (listen to [H+])(listen to [H+])Peripheral Peripheral ChemoreptorsChemoreptors (listen to [H+])(listen to [H+])

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Effect of pH on RespirationEffect of pH on Respiration

Changes in Respiration Rate not due Changes in Respiration Rate not due to COto CO22

Metabolic AcidosisMetabolic AcidosisMetabolic AlkalosisMetabolic Alkalosis

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Summary of ventilation controlSummary of ventilation control

Respiration is regulated byRespiration is regulated by

PO2PO2via via chemoreceptorschemoreceptors (carotid bodies in the arteries)(carotid bodies in the arteries)

PCO2PCO2via via chemorecptorschemorecptors for H+ in both the brain and for H+ in both the brain and

body.body.pH pH

via the same via the same chemorecptorschemorecptors in brain and bodyin brain and bodyDirect voluntary controlDirect voluntary control

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Exchange of gassesExchange of gasses

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Respiratory QuotientRespiratory Quotient

Ratio of: CORatio of: CO22 produced ÷ produced ÷ OO22 consumedconsumed

Some Respiratory Quotients for Some Respiratory Quotients for different foodsdifferent foods

Most combined diets = .8Most combined diets = .8Carbohydrate = 1Carbohydrate = 1

Fat = .7Fat = .7Protein = .8Protein = .8

Lets simplify this accounting of Gas Lets simplify this accounting of Gas exchangeexchange

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Daltons LawDaltons Law

In a mixture of gasses each gas behaves In a mixture of gasses each gas behaves as if it is independent of the other as if it is independent of the other

gasses.gasses.

Daltons LawDaltons Law

At sea level air is 760 mmHgOxygen only makes up 21% of

airTherefore the partial pressure

of oxygen =

760 X .21 = 160 mmHg

In air PO2 = 160mmHg

Henry’ s LawHenry’ s Law

The amount of gas The amount of gas dissolved in a solution dissolved in a solution will be directly will be directly proportional to the proportional to the partial pressure of the partial pressure of the gas with which the liquid gas with which the liquid is in equilibrium.is in equilibrium.

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Gas Exchange in partial PressuresGas Exchange in partial Pressures

In Pulmonary In Pulmonary venulesvenulesOxygen POOxygen PO22 = 100mmHg= 100mmHgCarbon dioxide COCarbon dioxide CO22 = 40mmHg= 40mmHg

In Pulmonary ArteriesIn Pulmonary ArteriesOxygen POOxygen PO22 = 40 mmHg= 40 mmHgCarbon dioxide COCarbon dioxide CO22 = 46mmHg= 46mmHg

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Ventilation of lungs should match Ventilation of lungs should match metabolismmetabolism

Hypoventilation = Increase in ratio of COHypoventilation = Increase in ratio of CO22production to ventilationproduction to ventilationHyperventilation = decrease in ratio of COHyperventilation = decrease in ratio of CO22production to ventilationproduction to ventilation

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Pulmonary saturation of OxygenPulmonary saturation of Oxygen

Ventilation PerfusionVentilation Perfusion

In the healthy lungs blood leaves fully saturated In the healthy lungs blood leaves fully saturated with oxygenwith oxygen

Ventilation PerfusionVentilation Perfusion

In the healthy lungs blood leaves fully saturated In the healthy lungs blood leaves fully saturated with oxygenwith oxygenLung capillaries Lung capillaries vasoconstrictvasoconstrict in response to low in response to low OO22

VentilationVentilation-- Perfusion inequalities can lead to reduced Perfusion inequalities can lead to reduced Oxygen levels in bloodOxygen levels in blood

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Transport of Oxygen in bloodTransport of Oxygen in blood

Less than 2% of Oxygen in blood is found freely Less than 2% of Oxygen in blood is found freely dissolved in plasma.dissolved in plasma.

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Carbon Dioxide in BloodCarbon Dioxide in Blood(normal person generates ~ 200ml/min)(normal person generates ~ 200ml/min)

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Carbon Dioxide in BloodCarbon Dioxide in Blood(normal person generates ~ 200ml/min)(normal person generates ~ 200ml/min)

10% dissolved in plasma10% dissolved in plasma30% bound to Hemoglobin30% bound to Hemoglobin60% converted to Bicarbonate60% converted to Bicarbonate

Hydrogen Ion RegulationHydrogen Ion Regulation

CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+

Carbonic Anhydrase

Hydrogen Ion buffer system

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Effect of pH on Hemoglobin Effect of pH on Hemoglobin bindingbinding

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Control of Ventilation during Control of Ventilation during ExerciseExercise

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