Respiratory 5 Flashcards by Jhaunte Braithwaite

Ventilation is subject gl modulation and control by…

CNS

Chemical factors

Peripheral factors

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What are the sensors of the respiratory system?

Chemoreceptors(central and peripheral)

Mechanoreceptors(joint, muscle and pulmonary receptors)

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What are the effectors of the respiratory system?

Respiratory muscles-diaphragm, intercostals, abdominal muscles

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What are the parts of the respiratory control center?

Pons and medulla

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What controls voluntary control of the respiratory system?

Cerebrum

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What parameters are monitored in the respiratory system?

PCO2

pH
PO2
Stretch
Irritation

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What are the neural control centers of the respiratory system?

Cerebrum- voluntary control

Medulla oblangata- basic rhythmic pattern of breathing

Dorsal Respiratory Group(DRG)
Ventral Respiratoru Group(VRG)
Central Pattern Generator

Pons

Pneumonic center
Apneuistic center

Emotional centers- anxiety, fear, rage

Hypothalamus
Limbuc system

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Describe Dorsal Respiratory Group(DRG)

Inspiratory (I) neurons
Inspiratory center
Motor neuron control of diaphragm and external intercostal muscles
Maintains a constant breathing rhythm
Functions mainly in quiet inspiration
When DRG activity ceases- expiration occurs
Input is from the vagus and glossopharyngeal nerves and output is via phrenology nerves

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Describe the ventral respiratory Group (DRG)

Intense inspiration (I+) neurons
Expiration (E) neurons

Functions mainly in forced breathing
Activate expiratory and inspiratory centers
Motir neuron control of accessory respiratory muscles

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Describe Central Pattern Generator

Pre-Botzinger complex-contained within the DRG and VRG complex
Pacemaker- like activity seen in experiments, exact description is uncertain
Injury abolishes rhythmic breathing

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Describe VRG & DRG activity

Pattern of activity the DRG & VRG neurons is “ramp-like” I.e. Action potential frequency increases gradually till it reaches a crescendo

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What is the Pneumonic center?

Upper pons
Decreases the depth and duration if inspiration
Possibly involved in regulation of inspiratory volume and therefore respiratory rate

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Describe the apneustic center

Lower pons
Sends signals to prevent switching off of inspiration
Increases the depth and duration of inspiration

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What are the typ3s of chemoreceptors?

Central and peripheral

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Where are central chemoreceptors located?

In the ventral surface of the medulla

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What are the effects of the central chemoreceptors ?

Responds to a change in PaCO2 and pH of the Cerebrospinal fluid(CSF)

CSF is separated from the blood by the blood brain barrier which is largely impermeable to H+ and HCO3-
Therefore metabolic acidosis or alkalosis has relatively little effect of CSF pH
The blood brain barrier is very permeable to O2 to. CO2
PCO2 has a strong effect on CSF pH and is therefore a powerful stimulus for ventilation

What is the most important chemical controller of ventilation?

Carbon dioxide

If CSF CO2 levels are high if blood CO2 levels are high

Results in increased breathing rate and ventilation

Where are peripheral chemoreceptors located?

In the carotid and aortic bodies

Describe peripheral carotid bodies

Detect changes in PaCO2, PaO2 and pH

Carotid body

Small (2 mm) sensory organ
Bifurcation of the carotid artery
Afferents feed CNS via theglossopharyngeal nerves

Aortic body
-Multiple bodies along aorta- afferents feed CNS via vagus nerve

Glomus cells- site of chemoreception

What is the Glomulusvcell response to increased PCO2 & H+?

Increased PaCO2
Causes acidification which also causes depolarization
-Increased ventilatory drive

Increased H+
Causes acid loading into cell-depolarization
-Increased ventilatory drive

What is the Glomus cell response to hypoxia?

Decreased PaO2
-depolarizes glomus cell stimulates afferents to the CNS

-Increased ventilatory drive

What are the respiratory reflex pathways?

Pulmonary stretch pathways
Irritant receptors
J receptors
Proprioceptors

Describe the action of stretch recept9rs

Lie in the smooth muscle layer of the airways

Fire in the proportionate response to extent of inflation

-Pulmonary stretch associated with lung inflation terminate inspiration in a reflex that prevents over inflation of the lung -Hering Breuer reflex

Describe the action of the muscle and joint receptors

Located in th3 chest wall

Sense chest wall movement and the effort involved in breathing

-Stimulates increased force of inspiration and expiration

Limb joints have similar effects during exercise

Describe the action of irritant receptors

Located in the epithelium of large conducting airways - Senses, dust, chemicals, smoke, ammonia, cold air - Effect is to stimulate bronchoconstriction, mucus secretion and coughing - Protects the respiratory zone

Describe the juxtapulmonary capillary receptors

- J receptors, located in alveolar walls - Unmyelinated nerve fibers(C fibers) - Senses chemicals, stretch, pulmonary edema - Causes bronchoconstriction, mucus secretion and shallow breathing

Describe the integrated ventilatory response

Changes in PaCO2, pH, and PaO2 rarely occur in isolation - Changes in activity and the environment initiate the integrated ventilatory response that involve changes in the cardiopulmonary system - Respiratiry center is forced to make choices about an appropriate ventilatory response - Generally output from the respiratory center is designed to optimize PaCO2 but, changes in the other parameters influence system sensitivity

How do chemoreceptors respond to the integrated response?

- Carotid response: detect increased PaCO2 but only increase ventilation slightly (20%) ; immediate response - Central chemoreceptors detect PaCO2 and dominates the ventilatory response within minutes - PaCO2 of arterial blood is an extremely potent ventilatory stimulus Modest changes in PaO2 has little effect on ventilation (must be below 60 mm Hg) -The response to PaCO2 is potentiated by low PaO2

What are the responses of the integrated response?

- Increased ventilation—> PaO2 increases and PaCO2 falls - Respiratory control centers seek to optimize PaCO2 - Mild hypoxia is overridden to stabilize CO2 - Comditions that decrease PaO2 usually result in increased PaCO2 and lowered pH

What is the clinical correlation of PaCO2?

In some chronic diseases, where PaCO2 is high but pH compensated, the hypoxia drive becomes more important (since the PCO2 response is largely due to change in pH) -Example: In patients with an acute exacerbation of COPD, administering O2 may help normalize PaO2 but can suppress respiration A titrated oxygen therapy has to be done for these patients

Explain the control of respiration at low oxygen tensions: high altitude

1. Decreased barometric pressure 2. Decreased PIO2 3. Decreased PAO2(hypoxia) 4. Decreased PaO2(hypoxemia) 5. Increased chemoreceptor activity, pulmonary vasoconstriction 6. Hyperventilation, increased cardiac output 7. In hours to days—> increased PAO2 and PaO2, decreased PACO2(hypocapnia & respiratory alkalos8s) 8. Increased 2,3 DPG 9. Months to years- increased erythropoietin, angiogenesis, ventricular remodeling

Explain the control of respiration during exercise

1. Mild to moderate exercise- increased oxygen consumption and CO2 production - stretching of muscles and tendons 2. Increased ventilation, increased CO2 removal 3. Unchanged arterial pH 4. Increased intensity-lactic acid formation, further increase in ventilation, increased cardiac output 5. Metabolic acidosis ensues, tidal volume continues to increase until it is limited or exhaustion. Occurs