Control of RespirationControl of Respiration

Week 5Week 5

Dr. Walid DaoudDr. Walid Daoud

A. ProfessorA. Professor

Non-Chemical (Nervous) Non-Chemical (Nervous) Regulation of RespirationRegulation of Respiration

11--Afferents from higher centers Afferents from higher centers (Cerebral cortex)(Cerebral cortex) Voluntary RespirationVoluntary Respiration::

Example:Example: talking, singing are controlled talking, singing are controlled expiratory efforts and expiration occurs at theexpiratory efforts and expiration occurs at the

end of each expiratory effortend of each expiratory effort.. Pathway: Pathway: excitatory and inhibitory afferentsexcitatory and inhibitory afferents

pass from cortex to RC neuron in brain stem orpass from cortex to RC neuron in brain stem or bypass directly to spinal motor neuron ofbypass directly to spinal motor neuron of

respiratory musclesrespiratory muscles..

Forms of Voluntary RespirationForms of Voluntary Respiration

11--Voluntary HyperventilationVoluntary Hyperventilation:: Its duration is limited by CO2 level inIts duration is limited by CO2 level in

blood. When CO2 decreases, respirationblood. When CO2 decreases, respiration stops for a while and is resumed againstops for a while and is resumed again

when CO2 accumulates and reaches itswhen CO2 accumulates and reaches its normal levelnormal level..

Forms of Voluntary RespirationForms of Voluntary Respiration

22 - -Voluntary Apnea (Breath Holding)Voluntary Apnea (Breath Holding)::

Voluntary stop of breathing e.g, swimmingVoluntary stop of breathing e.g, swimming

but after 45-60 sec. the person has desire tobut after 45-60 sec. the person has desire to

breathe (breaking point) due to decrease inbreathe (breaking point) due to decrease in

arterial PO2 and increase in arterial PCO2arterial PO2 and increase in arterial PCO2..

This causes chemical drive of respirationThis causes chemical drive of respiration..

Voluntary breath holding can be Voluntary breath holding can be prolonged byprolonged by::

11--Initial hyperventilation before breath holdingInitial hyperventilation before breath holding..

22--Prior inhalation of pure O2 for 1 minPrior inhalation of pure O2 for 1 min..

33--Hold breath in full inspiratory positionHold breath in full inspiratory position..

44--Viscerel reflexes e.g, swallowingViscerel reflexes e.g, swallowing..

II-Afferent from Respiratory II-Afferent from Respiratory MechanoreceptorsMechanoreceptors

11 - -In upper respiratory passagesIn upper respiratory passages::

Irritant receptors: Irritant receptors: in resp. mucosain resp. mucosa

Stimulus: Stimulus: mechanical (dust, mucus, food)mechanical (dust, mucus, food)

ResponseResponse::

--CoughCough..

- - SneezingSneezing..

- - BronchoconstrictionBronchoconstriction..

Cough ReflexCough Reflex

Stimulus:Stimulus: irritation, congestion, inflammation irritation, congestion, inflammation

Receptors:Receptors: free nerve endings of vagus free nerve endings of vagus..

AfferentsAfferents via vagus via vagus..

Cough center:Cough center: in medulla oblongata in medulla oblongata..

EfferentsEfferents to abdominal muscles which to abdominal muscles which contract increasing intra-abdominal contract increasing intra-abdominal pressurepressure..

Mechanics of CoughMechanics of Cough

11 - -Inspiratory phaseInspiratory phase..

22 - -Compressive phaseCompressive phase..

33 - -Expiratory blast phaseExpiratory blast phase..

Sneezing ReflexSneezing Reflex

Stimulus:Stimulus: irritation of nasal mucosa irritation of nasal mucosa..

AfferentAfferent to medulla via trigeminal nerve to medulla via trigeminal nerve..

Sneezing center in medullaSneezing center in medulla..

EfferentEfferent to expiratory muscles which to expiratory muscles which contract with opened glottiscontract with opened glottis..

II-Afferent from Respiratory II-Afferent from Respiratory MechanoreceptorsMechanoreceptors

22 - -Lung Stretch ReceptorsLung Stretch Receptors:: Lung contains 2 types of receptorsLung contains 2 types of receptors:: . .Slowly adapting receptors (SAR)Slowly adapting receptors (SAR)::

stretch receptorsstretch receptors.. . . Rapidly adapting receptors (RAR)Rapidly adapting receptors (RAR)::

- - Irritant receptorsIrritant receptors.. - - J-receptorsJ-receptors..

Stimulated receptors send afferent impulses toStimulated receptors send afferent impulses to RC in medulla via vagusRC in medulla via vagus . .

Hering-Breuer reflexHering-Breuer reflex

III-Afferent from chest wall receptorsIII-Afferent from chest wall receptors

In chest wall muscle and their tendonsIn chest wall muscle and their tendons

Afferent to RC via vagus to inform about Afferent to RC via vagus to inform about chest wall position and respiratory effortschest wall position and respiratory efforts

Inhibit DRG to stop inspirationInhibit DRG to stop inspiration..

These receptors determine tidal volume in These receptors determine tidal volume in human adultshuman adults..

IV-Afferents from proprioceptorsIV-Afferents from proprioceptors

Afferents from skeletal muscles, tendons Afferents from skeletal muscles, tendons and ligaments during exerciseand ligaments during exercise..

Stimulated by movement of muscles and Stimulated by movement of muscles and jointsjoints..

Causes reflex stimulation of ventilationCauses reflex stimulation of ventilation..

V-Afferents from cardiovascular systemV-Afferents from cardiovascular system

11--Arterial baroreceptors (high pressureArterial baroreceptors (high pressure

receptors):receptors): in aortic arch and carotid sinus in aortic arch and carotid sinus..

22--Atrial receptors (low pressure receptors)Atrial receptors (low pressure receptors)::

In right atrium and big veinsIn right atrium and big veins

VI-Visceral reflexesVI-Visceral reflexes

11 - -SwallowingSwallowing..

22 - -HiccupHiccup..

HypoxiaHypoxia

It is oxygen deficiency at tissue levelIt is oxygen deficiency at tissue level..

TypesTypes::

11 - -Hypoxic hypoxiaHypoxic hypoxia..

22 - -Anemic hypoxiaAnemic hypoxia..

33 - -Stagnant hypoxiaStagnant hypoxia..

44 - -Histotoxic hypoxiaHistotoxic hypoxia..

Hypoxic hypoxiaHypoxic hypoxia

It is caused by inadequate oxygenation It is caused by inadequate oxygenation or decreased PO2 in arterial bloodor decreased PO2 in arterial blood..

CausesCauses::

11 - -Low O2 tension in inspired airLow O2 tension in inspired air..

22 - -Pulmonary disordersPulmonary disorders::

. . Impaired ventilationImpaired ventilation..

. . Impaired perfusionImpaired perfusion..

33 - -Shunting of venous into arterial bloodShunting of venous into arterial blood..

Anemic hypoxiaAnemic hypoxia

It occurs when there is deficiency of Hb It occurs when there is deficiency of Hb capable of carrying O2capable of carrying O2..

CausesCauses::

11 - -Insufficient Hb (anemias)Insufficient Hb (anemias)..

22 - -CO poisoning (carboxy-Hb)CO poisoning (carboxy-Hb)..

Stagnant hypoxiaStagnant hypoxia

It occurs due to inadequate blood flow to It occurs due to inadequate blood flow to tissue or slow circulationtissue or slow circulation..

CausesCauses::

11 - -GeneralizedGeneralized..

22 - -LocalizedLocalized..

Histotoxic hypoxiaHistotoxic hypoxia

It occurs when tissues can not utilize O2It occurs when tissues can not utilize O2..

CausesCauses::

11 - -Cyanide poisoningCyanide poisoning..

22 - -Alcohol or narcotic poisoningAlcohol or narcotic poisoning..

Characteristics of different types of hypoxiaCharacteristics of different types of hypoxia

HypoxicHypoxicAnemicAnemicStagnantStagnantHistotoxicHistotoxicArterial PO2Arterial PO2

O2 contentO2 content

% %saturationsaturation

Venous PO2Venous PO2

O2 contentO2 content

% %saturationsaturation

CyanosisCyanosis

↓↓

↓↓

↓↓

↓↓

↓↓

↓↓

presentpresent

normalnormal

↓↓normalnormal

↓↓

↓↓

↓↓

absentabsent

absentabsent

normalnormal

normalnormal

normalnormal

↓↓

↓↓

↓↓

presentpresent

normalnormal

normalnormal

normalnormal

↑↑

↑↑

↑↑

absentabsent

CyanosisCyanosis

It is bluish coloration of skin and mucous It is bluish coloration of skin and mucous membranes due to presence of membranes due to presence of increased amount of reduced increased amount of reduced hemoglobin more than 5 grams / 100 ml hemoglobin more than 5 grams / 100 ml capillary bloodcapillary blood..

TypesTypes::

11 - -CentralCentral..

22 - -PeripheralPeripheral..

CyanosisCyanosis

CausesCauses::

11 - -hypoxic hypoxiahypoxic hypoxia..

22 - -stagnant hypoxiastagnant hypoxia..

33 - -all causes of asphyxiaall causes of asphyxia..