Respiratory Control Flashcards by Camelita Thrift

_____________ refers to the generation and regulation of rhythmic breathing and its modification by input of information from higer brain centers and specialized sensory receptors.

Ventilatory control

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_________ is to minimize work.

Mechanical perspective

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________ is to maintain blood gas levels and specifically to regulate arterial PCO2.

Physiological perspective

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What are the three goals of breathing?

Minimize work- Mechanical perspective
Maintain blood gas levels and to regulate arterial pCO2- Physiological perspective
Maintain the acid-base environment of the brain trhough the effects of ventilation on arterial pCO2

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What are the elements of the respiratory control system?

Sensors
- Monitor blood, CSF and lung volume/stretch
Controller
- Integrates and coordinates the information and sends signals to the effectors
Effectors
- Produce change in ventilatory pattern

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____________ is demonstrated with breath holding.

Voluntary control

NOTE: Voluntary control competes with involuntary mechanisms. Automatic control eventually overpowers the voluntary efforts thereby limiting the duration of the breath.

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The pneumotaxic center is found in the ________.

Upper Pons

*This center inhibites inspiration

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Separation of the _______ and _______ allow rhythmic breathing to ensue.

Pons; medulla

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What is the effect of transection of the upper pons on respiration?

Decreased frequency and increased tidal volume (apneusis)

REMEMBER: The pneumotaxic center is found in the pons and functions to inhipit inspiration

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What affects would transection across the lower pons have on respiration?

Gasping (with or wothout intact vagus)

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What affects would transection across thelower medulla have on respiration?

Complete respiratory arrest (apnea)

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Pre-Botzinger Complex

the main location of the rhythmic pattern generation circuitry involved in breathing.

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Dorsal respiratory group located in the dorsomedial region of the medulla is primarily involved in _________.

Inspiration

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What nucleus is found in the dorsal respiratory group? What is is role in respiration?

Nuclus Tractus Solitarii

Integrates inputs from the 9th and 10th cranial nerves
Responds to inflation/irritant recepts of the lungs and airways
Receives info about PO2, PCO2, and pH from peripheral chemoreceptors and systemic BP
Receives info from pulmonary stretch receptors

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Types of respiratory neurons

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Ventral Resiratory group is located in the ventrolateral region of the medulla and has a major influence on __________.

Expiration

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What nuclei are found in the ventral respiratory group?

Rostral nucleus retrofacialis
Caudal nucleus retroambiguus
Nucleus paraambiguus
Inspiratory and expiratory neurons
- Primary function is to drive spinal respiratory neurons innervating the intercostal and abdominals or upper airway muscles of inspiration

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Which nucleus of the VRG has connections to the contralateral external intercostals, and to i-cells and E-cells within the medulla?

Nucleus Retroambiguus

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The VRG nucleus is made primarily of vagal motor neurons that inenrvate the laryngeal and pharyngeal muscles and activate during both inspiration and expiration.

Paraambiguus

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____________ center is comprised of the Kolliker-Fuse and nucleus parabrachialis medialis and the fine tuning centers.

Pneumotaxic

Located in the upper pons
Premature termination of inspiratory ramp
Shorten of inspiration that results in frquency modulation of breathing

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The apneustic center is located in the _______.

Lower pons

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Phases of the respiratory cycle

Inspiration

Ramp-like increase in inspiratory neuron firing rate

Off Switch

Rapid Decline in inspiratory neuron firing rate

Exhalation

Paradoxical increase in inspiratory neuron firing that brakes the expiratory phase
Cells become silent in Phase II

Where are peripheral chemoreceptors located?

Carotid bodies (CN IX)

Aortic bodies (CN X)

Peripheral recepheral receptors are uniquely sensitive to ________.

Oxygen

NOTE: PO2 does not play a significant role in the regulation of normal ventilation until levels decrease below 60 mmHg

What are peripheral receptors activated by?

* Acidic pH * Increased PaCO2 * Decreased PaO2

What function do carotid bodies play in respiration?

* Type II cells, glomus, found within carotid bodies contain large numbers of synaptic vessels that contian **neurotransmitters**. * The neurotransmitters are released in response to **increased PCO2, increased H+, decreased PO2** in the arterial blood * The neurotransmitters act on adjacent nerve terminals and signals from these terminals are transmitted to the **medullary respiratory control center** through the carotid sinus nerve

What's the cascade of events involved in carotid body O2 sensor stimuation by a decreased in PaO2?

1. Low PO2 2. K+ Channels to close 3. Cell depolarizes 4. Ca2+ channels open and Ca2+ enters 5. Exocytosis of **dopamine-containing vesicles** 6. Signals to medullary centers to **increase ventilation**

Central chemoreceptors are located within the _____ and respond to pH of \_\_\_\_\_\_\_\_.

Medulla; CSF

How is pH the most potent and primary stimulus of central chemoreceptors, if H+ can't cross the blood brain barrier?

* CO2 crossed the blood brain barrier * CO2 binds with H2O to produce carbonic acid * Carbonic acid dissociates to HCO3- and H+ \*So an increase in CO2 leads to and increase in H+, which decreases the pH

HCO3- is controlled by the \_\_\_\_\_\_\_\_\_.

Choroid plexus

During inspiration, the activity of inspiratory neurons increases steadily, apparently through a __________ mechanism.

Positive feedback

The ventilatory response to hypercapnia is enhanced by \_\_\_\_\_\_\_.

Hypoxia

Peripheral chemoreceptors are important to patients with what conditions?

COPD Chronic lung disease **REMEMBER:** In these conditions, CO2 retention is inevitable. Ventilation will need to be increased to maintain balance

Pulmonary receptors are ________ (slow/fast) adapting.

Slow

Herring- Breaur reflex

* Protects against over-expansion of the lung during strenous exercise * Stimulated by increased lung volume * Mediated by **vagal afferents** located within the smooth muscle of large and small airways * Triggers the cut-off switch to abruptly terminate inspiratory activity

Tidal volume in excess of ____ liter causes the lung-stretch receptors to signal the brainstem to shut-off inspiration.

Diving reflex

* Cold water on the nose and facial region triggers **apnea** and bradycardia. * Provides protection from aspiration of water during the initial stages of drowning

Sneeze reflex

* Triggered by activation receptors in the nose * Triggers deep inspiration followed by an explosive expiration trhough the nose * Helps to remove foreign materail

Aspiration or sniff reflex

Elicited by stimulation of mechanical receptors in nasopharynx to the pharynx.

Where are irritant receptors found?

Trachea

Irritant recepts impulses are transmitted via \_\_\_\_\_\_\_\_\_\_.

Myelinated vagal afferents

Results of irritant receptor stimulation

* Increased airway resistance * Relex apnea * Coughing **NOTE:** Irritant receptors are referred to as _rapidly adapting_ pulmonary stretch receptors

Slow adapting pulmonary stretch receptors transmit info via \_\_\_\_\_\_\_\_\_\_

Myelinated vagal afferents

Slowly adapting pulmonary stretch receptors are activated by \_\_\_\_\_\_\_\_\_

Lung inflation **NOTE:** These receptors are significant in people with OPD

Juxta-alveolar receptors transmit info via \_\_\_\_\_\_\_\_\_\_.

Unmyelinated vagal C-fibers

What type of breathing are Juxta-alveolar receptors involved in?

Rapid, shallow breathing \*As seen in pulmonary edema

Where are sensory receptors found?

* Intercostal and rib joint * Accessory muscles of respiration * Tendons

Sensory receptors respond to \_\_\_\_\_\_\_.

Changes in length and tension of the respiratory muscles \*These receptors participate in terminating inspiration

Apneustic breathing

Sustained inspiration separated by brief periods of exhalation

Cheyne-Stokes Respiration is common in people with what conditions?

* Head trauma * CNS disease state * Increased intracranial pressure

Cheyne-Stokes Respiration

Characterized by varying tidal volume and respiratory frequency that progressively increase over several breaths

Central alveolar Hypoventilation (Odine's Curse)

* Must be conscious to take a breath * Suffiecient "voluntary" control over ventilation * Distractions result in severe hypoventilation or apnea

Treatment for Odine's Curse

Diaphragmatic pacing Mechanical ventiltion