RESPIRATORY RESPIRATORY PHYSIOLOGYPHYSIOLOGY

Agaton T. Panopio, Jr., MD, MHPEdAgaton T. Panopio, Jr., MD, MHPEd

Respiratory Patterns

EupneaNormal breathing

ApneaTemporary cessation of breathing

SighA larger than normal breath occurring automatically at regular intervals to counteract collapse of alveoli

Respiratory Patterns

Yawning - Pandiculation

An exaggerated sigh

May be due to:

A reflex occurring if there is O2 need

Boredom

A primitive behavior to warn others

Contagious ?

Yawning

Increase in dopamine, serotonin, acetylcholine, nitric oxide, ACTH-related peptides and oxytocin

Decrease in endorphins

Yawning

Expansion of the chest and descent of diaphragm and larynx

Elevation of ala nasi and soft palate

Downward and backward movement of the tongue

Abduction of vocal cords

Wide opening of the mouth

Yawning

Contraction of tensor veli palatini muscle

Closure of the eyes and lacrimation

Pulling of head backwards

Stretching of arms sideward, and forearms upward

Vasoconstriction esp in digits

Cardiac acceleration

Respiratory Patterns

Tachypnea (Polypnea)

An increase in respiratory rate

May be reflex in origin

Hyperpnea

An increase in rate and depth of respiration, which matches an increase in metabolic demand as in exercise

Respiratory Patterns

HyperventilationAn increase in rate and depth of respiration, which exceeds metabolic demand as in high altitudes

HypoventilationA decrease in rate and depth of respiration, which may occur as compensation to metabolic alkalosis

Respiratory Patterns

DyspneaConsciousness of the necessity for increased respiratory efforts, seen in pulmonary congestion of left heart failure

Kussmaul respirationExtremely deep, rapid breathing due to intense stimulation of the respiratory center, seen in metabolic acidosis

Respiratory Patterns

OrthopneaDyspnea in the recumbent position

Cheyne-Stokes respirationCycles of gradual increase followed by gradual decrease in tidal volumes, followed by equal periods of apnea, seen in bilateral cortical disease, congestive heart failure, or during sleep at high altitudes

Respiratory Patterns

Biot’s respirationBreaths of equal volume separated by unequal periods of apnea, seen in medullary or pontine lesions

GaspingMaximal, brief inspiratory efforts separated by long periods of expiration, seen in severe anoxia or terminal brain stem lesions

Respiratory Patterns

Apneusis

Prolonged inspiration separated by brief expirations

Rarely seen in humans

Due to lesion in pneumotaxic center

Respiratory Centers

Centers at the Pons

The Pons modulates – but is not essential for – respiratory output

Pontine Respiratory Group

Apneustic Center

Centers at the Pons

Pontine Respiratory GroupPneumotaxic Center (Rostral Pons)

Nucleus parabrachialis medialisKolliker-Fuse nucleus

Promotes coordinated respirations by modulating activity of Apneustic Center

Not necessary for eupnea

Centers at the Pons

Apneustic Center (Caudal Pons)

Stimulation causes apneuses

Presently, the role of the Apneustic Center on respiration is still not clearly understood

Centers at the Medulla

Dorsal Respiratory Group (DRG)

Primarily contains inspiratory neurons

Located at Nucleus Tractus Solitarius

Responsible for processing of sensory inputs

Inputs come from CN IX and X, as well as from peripheral chemoreceptors

Centers at the Medulla

Ventral Respiratory Group (VRG)Contains both inspiratory and expiratory

neuronsContains motor neurons that innervate

the muscles of the larynx, pharynx, viscera of thorax and abdomen

Receives sensory information from DRG

Centers at the Medulla

Ventral Respiratory Group

Rostral VRG

Botzinger complex or Nucleus Retrofacialis

Contain interneurons that drive expiratory activity of the caudal region

Centers at the Medulla

Ventral Respiratory Group

Intermediate VRG

Nucleus Ambiguus

Nucleus Para-ambigualis

Contain somatic motor neurons which supply the upper airways

Centers at the Medulla

Ventral Respiratory Group

Intermediate VRG

Also contains premotor neurons that project to inspiratory motor neurons in the spinal cord and medulla

Centers at the Medulla

Ventral Respiratory GroupIntermediate VRG

At the rostral pole of the intermediate VRG is a group of inspiratory neurons

PreBotzinger complexGenerates respiratory

rhythmicity

Centers at the Medulla

Ventral Respiratory Group

Caudal VRG (Nucleus Retroambigualis)

Contains premotor neurons that travel down the spinal cord to

synapse on motor neurons that innervate accessory muscles of expiration

Centers at the Medulla

Respiratory RhythmicityRestricted Site Models

Nucleus Tractus Solitarius (Cajal)Reported that neurons in the NTS receive afferents from pulmonary stretch receptors and project directly to the phrenic motor nucleus

Centers at the Medulla

Respiratory RhythmicityRestricted Site Models

PreBotzinger Complex (Suzue)Neurons at the complex generate rhythmic motor

output in the phrenic and hypoglossal nerves; destruction of these neurons causes respiratory outputs to stop

Centers at the Medulla

Respiratory RhythmicityDistributed Oscillator Model

There is more than one Central Pattern Generator (CPG)

Parafacial respiratory groupTRH

Only one CPG exists for eupnea, the rest only augment the rhythm

Centers at the Medulla

Respiratory Rhythmicity

Emergent Property Model (Lumsden)

No individual region of DRG or VRG is sufficient to generate a rhythm, but that many of them are necessary

Center at the Spinal Cord

Serves as site of integration of descending impulses from higher centers

Nerve fibers:Alpha motor neurons

Innervate extrafusal fibersGamma efferent neurons

Innervate intrafusal fibers

Normal Ventilation

Spontaneous depolarization of Central Pattern Generator (CPG)

Dorsal Respiratory Group

Ventral Respiratory Group

Normal Ventilation

Intermediate Ventral Respiratory Group

Premotor neurons project to inspiratory motor neurons in spinal cord and

medulla

Inspiration

Normal Ventilation

Intermediate Ventral Respiratory Group

Somatic motor neurons whose axons leave the medulla through CN IX and X

Maximize caliber of the upper airways during inspiration

Modulation of Respiration

Receptors In Airways and Lung Parenchyma

Provide feedback about lung volume and the presence of irritants

Slowly adapting pulmonary stretch receptors

Rapidly adapting pulmonary stretch receptors

C fiber receptors (J receptors)

Higher Brain Centers

Cerebral Cortex

Modulates the respiratory system by:

Sending axons to respiratory centers at the medulla

Sending axons to motor neurons that control muscles of respiration

Higher Brain Centers

Cerebral Cortex

Coordinates voluntary behaviors that use respiratory muscles

Voluntary hyperventilating

Breath-holding Speaking

Singing Whistling

Playing musical wind instruments

Higher Brain Centers

Cerebral Cortex

Coordinates complex non-ventilatory behaviors

Yawning Chewing

Swallowing Sucking

Defecating Grunting

Vomiting

Higher Brain Centers

Cerebral CortexLesions in specific areas of cerebral cortex

Abolish voluntary breath-holding(Respiratory apraxia)

Lesions in reticulospinal tractRespiratory failure while asleep (Ondine’s curse)

Other Centers

Limbic System and Hypothalamus

Modify respiration in affective states

Fear

Horror

Rage

Passion

Other Centers

Reticular Activating System

At brain stem

One of the sources of tonic drive to the respiratory CPG

Increase in drive occurs during arousal from sleep

Reflex MechanismsReflex Mechanisms

Receptors – stretch receptors in airwaysReceptors – stretch receptors in airways

ResponseResponse

Apnea/Decreased respirationApnea/Decreased respiration

BronchodilationBronchodilation

Hering-Breuer Inflation ReflexHering-Breuer Inflation Reflex

Stimulus – lung inflationStimulus – lung inflation

J receptors J receptors Irritant receptorsIrritant receptors

Stretch receptors in airwaysStretch receptors in airways

ResponseResponse

HyperpneaHyperpnea

Sigh responseSigh response

Reflex MechanismsReflex Mechanisms

Hering-Breuer Deflation ReflexHering-Breuer Deflation Reflex

Stimulus – lung deflationStimulus – lung deflationReceptorsReceptors

Stimulus – lung inflationStimulus – lung inflation

Receptors – stretch receptors in lungReceptors – stretch receptors in lung

Response Response

InspirationInspiration

Sigh responseSigh response

Reflex MechanismsReflex Mechanisms

Paradoxic Reflex of HeadParadoxic Reflex of Head

Stimulus – irritation at the noseStimulus – irritation at the nose

Receptors – nasal mucosa receptorsReceptors – nasal mucosa receptors

ResponseResponse

SneezeSneeze

BronchoconstrictionBronchoconstriction

Rise in BPRise in BP

Reflex MechanismsReflex Mechanisms

Sneeze ReflexSneeze Reflex

Sneeze

Almost always preceded by a deep inspiration

Initial increase in intrathoracic negative pressure against a closed glottis

Constriction of pharynx

Explosive forced expiration through the nose and mouth

Dislodges foreign bodies and mucus from nasal mucosa

Stimulus – irritation beyond the noseStimulus – irritation beyond the nose

Receptors – upper airway receptorsReceptors – upper airway receptors

ResponseResponse

CoughCough

BronchoconstrictionBronchoconstriction

Reflex MechanismsReflex Mechanisms

Cough ReflexCough Reflex

Cough

Upper airway causes

Inspiration is absent

Lower airway causes

Small inspiration

Cough

Forced expiration with closed glottis

Glottis opens suddenly

Pressure in the larynx falls

Trachea collapses

Cough

Brief but violent rush of air out of the trachea

Loosens mucus or foreign bodies and moves them upward

Stimulus – immersion of the face in waterStimulus – immersion of the face in water

Receptors – receptors in nasal mucosa Receptors – receptors in nasal mucosa and and faceface

ResponseResponse

ApneaApnea

Decreased heart rateDecreased heart rate

VasoconstrictionVasoconstriction

Reflex MechanismsReflex Mechanisms

Diving ReflexDiving Reflex

Stimulus – drugs in pulmonary Stimulus – drugs in pulmonary circulationcirculation

Receptors – J receptorsReceptors – J receptors

ResponseResponse

Apnea/TachypneaApnea/Tachypnea

BronchoconstrictionBronchoconstriction

Reflex MechanismsReflex Mechanisms

Pulmonary ChemoreflexPulmonary Chemoreflex

Stimulus – low Pa O2, low pHStimulus – low Pa O2, low pH

Receptors – chemoreceptorsReceptors – chemoreceptors

ResponseResponse

HyperpneaHyperpnea BronchoconstrictionBronchoconstriction

BradycardiaBradycardia VasoconstrictionVasoconstriction

Reflex MechanismsReflex Mechanisms

Arterial Chemoreceptor ReflexArterial Chemoreceptor Reflex

Stimulus – increased systemic BPStimulus – increased systemic BP

Receptors – baroreceptorsReceptors – baroreceptors

ResponseResponse

ApneaApnea BronchodilationBronchodilation

BradycardiaBradycardia VasodilationVasodilation

Reflex MechanismsReflex Mechanisms

Arterial Baroreceptor ReflexArterial Baroreceptor Reflex

StimulusStimulus

Stretch of muscle/tendonStretch of muscle/tendon

Movement of jointsMovement of joints

Receptors – muscle spindle, Golgi Receptors – muscle spindle, Golgi tendon organ, proprioceptorstendon organ, proprioceptors

Response - hyperpneaResponse - hyperpnea

Reflex MechanismsReflex Mechanisms

Reflexes From Muscles, Tendons, JointsReflexes From Muscles, Tendons, Joints

Stimulus – somatic painStimulus – somatic pain

Receptors – nociceptorsReceptors – nociceptors

ResponseResponse

HyperpneaHyperpnea

TachycardiaTachycardia

VasoconstrictionVasoconstriction

Reflex MechanismsReflex Mechanisms

Reflexes Due to PainReflexes Due to Pain

Central Chemoreceptors

Ventrolateral medullaStimulation leads to an increase in ventilation

Medullary rapheNeurons stimulated by acidosis contain

serotonin as transmitterNeurons inhibited by acidosis contain

GABA as transmitter

Central Chemoreceptors

Nucleus ambiguusNucleus tractus solitariusLocus ceruleusHypothalamus

Neurons are primarily sensitive to arterial hypercapnia, but actual parameter appears to be a low pH in or around the chemoreceptors

T H A N K Y O U !