RespirationRespirationGroup 5

PuentispinaPusing

RazalanRecio

3OTB

RESPIRATORY SYSTEM FUNCTIONSRESPIRATORY SYSTEM FUNCTIONS

• responsible for gaseous exchange between the blood and external environment.

• provides oxygen for metabolism in the tissues and removes carbon dioxide (the waste product of metabolism).

• facilitates sense of smell• can also produce speech• Can maintain acid-base balance, body water

levels and heat balance.

RespirationRespirationis the act of breathing

Processes/LevelsProcesses/Levels

External Respiration◦Absorption of O2 and removal of CO2 from the

bodyInternal Respiration

◦Utilization of O2 and production of CO2 by cells and the gaseous exchanges between the cells and their fluid medium

PASSAGEWAY of AIRPASSAGEWAY of AIR

Passageway of AirPassageway of Air

UPPER AIRWAYS

Nasal cavity pharynxlarynx

LOWER AIRWAYS

TracheaPrimary BronchiBronchial treeBronchiolesAlveoli

RESPIRATORY SYSTEM RESPIRATORY SYSTEM

Gas exchanging organ◦Lungs

Pump that ventilates the lungs◦Chest wall◦Respiratory muscles◦Areas in the brain

that control the muscles

◦Tracts◦nerves

THE LUNGSTHE LUNGS

the site of gas exchange and it occupies most of the thoracic cavity

divided into lobes: left lung (2 lobes); right lung (3 lobes)

has 2 pleural membranes

Between trachea and alveolar sacs -> airways divide 23 times◦1st 16 generation: conducting zone of the airways that transports gas from and to the exteriorBronchi, bronchioles, terminal bronchioles

◦Remaining 7 generations -> transitional and respiratory zones where gas exchange occursRespiratory bronchioles, alveolar ducts, alveoli

Pulmonary CirculationPulmonary Circulation

Blood-> pulmonary artery -> pulmonary capillary bed (oxygenated and returned to left atrium via pulmonary veins)

Bronchial arteries- small, separated, come from systemic arteries

Capillaries- drain into bronchial veins ; anastomose with pulmonary capillaries/veins

Bronchial veins- drain into azygos veins

Bronchial circulation nourishes bronchi & pleura

Pulmonary CirculationPulmonary Circulation

Pressure◦Pulmonary Circulation: 7mm Hg

Systemic Circulation- 90mm HgVolume

◦Pulmonary vessels at any one time =1LFlow

◦mean velocity at the root of pulmonary artery= about 40cm/s 0.75 secs- red cells traverse the pulmonary

capillaries at rest 0.3 s or less during exercise

What is Breathing?What is Breathing?

Breathing is the movement of air into and out of the lungs.

12-18 respirations/ min (adults)30-50 respirations/ min (infants)

*Patient Care skills by Pierson and Fairchild

12-15 respirations/ min (Ganong)

Control of BreathingControl of Breathing

Levels of ControlLevels of Control

Local ControlCentral Control

Local ControlLocal Control

Location: Alveoli, alveolar capillaries and bronchioles in localised areas of the lung

Role: To ensure blood and gas go to the appropriate parts of the lung for efficient gas exchange.

Local ControlLocal Control

When: There are localized changes in Co2 and O2

Mechanism:  Local adjustments to blood flow (lung perfusion) and oxygen delivery (alveolar ventilation) to alveoli

Local ControlLocal Control

Independent of brain’s activity

2 components > Lung perfusion > Alveolar ventilation

Lung PerfusionLung Perfusion

Ensures that arteriolar blood flow is diverted to where it is needed in the lung.

Vasoconstriction of arterioles supplying lung areas low in O2

Lung PerfusionLung Perfusion

Alveolar VentilationAlveolar Ventilation

Ensures optimum conditions for gas exchange.

Adjusts the size of the bronchioles in response to alveolar PCO2.

Alveolar VentilationAlveolar Ventilation

Local Control – V/Q RatioLocal Control – V/Q Ratio

Ventilation (V)-Perfusion(Q) ratio Ratio between the amount of air entering the

alveoli and the amount of blood draining into the lung.

Allows an assessment of the efficiency of gas exchange.

Local control aims at maintaining an optimal V/Q.

Central ControlCentral Control

Location:  The respiratory centres (pairs of nuclei located in the medulla oblongata and the pons) modified by sensory neurons(peripheral and in the brain’s cerebrospinal fluid) and higher centres (cerebral cortex).

Role: Adjust the depth and rate of ventilation

Central ControlCentral Control

When: During both normal breathing and also when there is a larger respiratory demand or conscious control is needed (e.g. during talking).

Mechanism: Both involuntary (respiratory reflexes involving sensory feedback) and voluntary (higher centres of the brain) control via the respiratory centres.

Central ControlCentral Control

Directs respiration via the respiratory centres of the brain.

Affect the rate and depth of breathing in response to various sensory and higher inputs.

2 Components:Voluntary Involuntary

Voluntary ControlVoluntary Control

Influenced indirectly by the cerebral cortex and affects the output of the respiratory centres in the medulla oblongata.

Influential factors include emotion, anticipation of exertion and activities requiring alteration to normal breathing (e.g. playing trumpet)

Involuntary ControlInvoluntary Control

Directs the depth and rate of breathing via outputs from the respiratory centres.

Ensure appropriate levels of ventilation.

Involuntary ControlInvoluntary Control

Normal Rhythmical Breathing – Respiratory Centers (Brain)

Rhythmicity Center – Medulla OblangataDorsal Respiratory groupVentral Respiratory group - output :

 apneustic and pneumotaxic centres (pons)

Involuntary Control – Normal Involuntary Control – Normal BreathingBreathing

Controlling CentersMedullaPonsRespiratory Neurons I Neurons – inspirationE Neurons - expiration

I neurons send out streamsof impulses which travel down

to the ANTERIOR HORN CELLSof the SPINAL CORD on the opposite

site and are relayed fromCERVICAL SEGMENTS

by the PHRENIC NERVESto the DIAPHRAGM and from

THORACIC SEGMENTS

by the INTERCOSTAL NERVESto the INTERCOSTAL MUSCLES

These nerve impulses cause the muscle of inspiration to contract

In the nucleus retroambiguus (NRA) E neurons in the upper end Inhibit

the I neurons during expiration

PNEUMOTAXIC CENTER (PTC)(nucleus parabrachialis)

Normal function unknown but may have a role in switching

between inspiration and expiration

MEDULLARY GROUPSThe dorsal group in the nucleus of the

tractus solitarius (NTS) contain I neuron.The ventral group in the nucleus NRA

contain both E and I neurons.Afferent impulses in the vagus from lung

stretch receptors inhibit I neuron discharge.

Inspiratory neurons inhibited

The muscles of inspiration relax

Expiration follows passively in quiet respiration

Expiratory (E) neurons are excited in force expiration

Respiratory CenterRespiratory Center

Normal Breathing CycleNormal Breathing Cycle

Inhalation occurs in first 2 seconds followed by 3 seconds of exhalation 

Inhalation: Within the first stage, the DRG (stimulated by the apneustic centres), enhance the activities of the inspiratory muscles

Exhalation: In the next 3 seconds, the pneumotaxic centres inhibit the apneustic centres resulting in unstimulated DRG. These no longer stimulate inhalation anymore, causing passive exhalation

Forced Breathing CycleForced Breathing Cycle

Inhalation: both the DRG and inspiratory centres of the VRG stimulate the contraction of inspiratory muscles and inhibition of the expiratory centres of the VRG. This leads to relaxation of expiratory muscles, resulting in inhalation

Forced Breathing CycleForced Breathing Cycle

Exhalation: The DRG and inspiratory centres of the VRG are inhibited. Meanwhile, expiratory centres of VRG bring about the contraction of expiratory muscles, causing forced expiration 

Respiratory CenterRespiratory Center

Involuntary control: Involuntary control: Respiratory ReflexesRespiratory Reflexes

 Normal pattern of breathing is modified via sensory reflexes in order to accommodate physiological changes and maintain homeostasis.

Receptors detect changes inside the body and send information to the central controllers.

Involuntary Control : Involuntary Control : Respiratory ReflexesRespiratory Reflexes

Output of the controllers is then modified changing the efferent signal to the effectors

StimulationChemicalMechanicalChanges in Blood Pressure

Chemoreceptor ReflexesChemoreceptor Reflexes

 Detect changes in the chemical composition of the blood and cerebrospinal fluid.

Central ChemoreceptorsPeripheral Chemoreceptors

  Hering-Breuer ReflexesHering-Breuer Reflexes

Function in controlling the inflation and deflation of the lungs during forced breathing.

Controls volume and stretch of lungs to avoid over expansion and over deflation.

Slowly adapting receptors (SARs)Inflation reflexDeflation reflex

  Rapidly adapting receptors and Rapidly adapting receptors and protective reflexesprotective reflexes

Rapidly adapting receptorsCoughingSneezingBronchoconstrictionTachypneaAspiration

J receptors: Inflammation and J receptors: Inflammation and EdemaEdema

 Stimulated by pulmonary edema and products of inflammation in the interstitium of the lungs.

Contributes to particular responses such as rapid shallow breathing,decreased tidal volume, increased respiratory rate, mucus secretion and cough.

Head’s Paradoxical ReflexHead’s Paradoxical Reflex

Presence of cold block on vagus nerve.Inflation is not inhibited in the lungs.Contributes to particular responses such

as rapid shallow breathing,decreased tidal volume, increased respiratory rate, mucus secretion and cough.

  Muscle spindle reflexesMuscle spindle reflexes

Muscle spindles are sensory receptors that are widely located in the intercostal muscleswithin the ribcage and are involved in a reflex arc not involving the medulla (sensory neurons synapse directly with motor neurons).

Baroreceptor ReflexesBaroreceptor Reflexes

 Affect respiratory frequency and tidal volume.

By decreased intrasinus pressure

Chemical ControlChemical Control of Respiration of Respiration

Chemosensitive Chemosensitive AreaArea

Additional neuronal area

Highly sensitive to changes in either blood PCO2 or hydrogen ion concentration -> excites portion of the respiratory center

Sensor neurons > Specially excited by hydrogen ion

Effect of CO2Effect of CO2

Indirect effect

React with water to form carbonic acid -> hydrogen and carbonate ion.

Easily passes through the blood-cerebrospinal fluid barrier.

Increae in CO2 -> increase in H ion in chemosensitive area

Explain the dominant role of CO2 in determining to Explain the dominant role of CO2 in determining to breathebreathe

An increased concentration of CO2 within the human body stimulates the respiratory system in order to restore the balance between O2 and CO2 concentrations. Therefore, breathing is initiated once the level of CO2 increases beyond the normal.

Experiment 5Experiment 5ResultsResults

After Normal Expiration After Over breathing After Half-Squat

Group 5 23.42 secs 43.19 secs 9.66 seconds

This Graph shows that the one with shortest time before breakout is during half squat followed by normal expiration and the one with longest time before breakout is during over breathing.

This graph shows the comparison between groups in the class. We can see that This graph shows the comparison between groups in the class. We can see that all (100%) groups agreed that their shortest time before breakout happens all (100%) groups agreed that their shortest time before breakout happens during half squats, 5 groups (except group 3, about 83.33% of class) has the during half squats, 5 groups (except group 3, about 83.33% of class) has the same result that their longest time before breakout happens after over same result that their longest time before breakout happens after over breathing and the second longest time is after normal expirationbreathing and the second longest time is after normal expiration

RATIONALERATIONALE

The shortest time before breakout is after doing half squats. During half squats, the oxygen and carbon consumption and carbon dioxide formation increases than normal and so there is an increase in ventilation. Ventilation begins immediately during the initiation of half squats before any blood chemicals have had time to change. The increase in respiration is due to direct transmission of neurogenic signals to the brain stem respiratory center causing the body to react (begin breathing/ begin the cycle-inspiration and expiration once again). Contrary to this is the reason why the longest time before breakout is during over breathing. The subject continuously breathes deeply for a short interval and then abruptly holds his breath. During over breathing, the person blows off too much carbon dioxide from the pulmonary blood while at the same time increasing blood oxygen. In this condition, it takes several seconds before the changed pulmonary blood can be transported to the brain ergo, inhibits excess ventilation. Once it is transmitted in the brain respiratory center, the center becomes depressed to an excessive amount and therefore the brain will respond and the breathing cycle begins once again.

Peripheral ChemoreceptorPeripheral Chemoreceptor

Detects changes in O2 in the blood

Located:Carotid bodies

(bifurcation of the common carotid > Hering Nerve > glossopharyngeal N. > dorsal respiratory area)

Peripheral ChemoreceptorPeripheral Chemoreceptor

Located:Aortic bodies(arch of

the aorta > Vagus Nerve > Dorsal respiratory area)

Peripheral ChemoreceptorPeripheral Chemoreceptor

Depletion of oxygen in arterial blood causes the stimulation of chemoreceptor area.

Glomus cells – synapse directly or indirectly to the nerve ending.

When does O2 becomes the primary stimulus When does O2 becomes the primary stimulus for breathing?for breathing?

When arterial carbon dioxide and hydrogen ion concentration remains normal despite increase respiration

Oxygen level is less than 60 mm Hg.

Which is the more important in respiration, Which is the more important in respiration, PO2 or PCO2?PO2 or PCO2?

The more important drive for respiration is the change in one's PCO₂, or the effect of carbon dioxide on the central chemoreceptors. This is because of the ready penetration of CO₂ to membranes, most especially at the blood-brain barrier.

Which is the more important in respiration, Which is the more important in respiration, PO2 or PCO2?PO2 or PCO2?

Proper delivery of oxygen can occur despite changes in lung ventilation on the other hand CO2 changes almost exactly inversely with the rate of ventilation

Breaking Point Breaking Point

Point at which breathing can no longer be voluntarily inhibited.

Breaking Point DelayBreaking Point Delay

Breathing 100% Hyperventilation

Raises alveolar PO2 initially thus breaking point is delayed.

CO2 is blown off ad arterial CO2 is lowered from the start thus breaking point is delayed