Respiratory Control Flashcards
_____________ 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
_________ is to minimize work.
Mechanical perspective
________ is to maintain blood gas levels and specifically to regulate arterial PCO2.
Physiological perspective
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
What are the elements of the respiratory control system?
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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
____________ 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.
The pneumotaxic center is found in the ________.
Upper Pons
*This center inhibites inspiration
Separation of the _______ and _______ allow rhythmic breathing to ensue.
Pons; medulla
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
What affects would transection across the lower pons have on respiration?
Gasping (with or wothout intact vagus)
What affects would transection across thelower medulla have on respiration?
Complete respiratory arrest (apnea)
Pre-Botzinger Complex
the main location of the rhythmic pattern generation circuitry involved in breathing.
Dorsal respiratory group located in the dorsomedial region of the medulla is primarily involved in _________.
Inspiration
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
Types of respiratory neurons
Ventral Resiratory group is located in the ventrolateral region of the medulla and has a major influence on __________.
Expiration
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
Which nucleus of the VRG has connections to the contralateral external intercostals, and to i-cells and E-cells within the medulla?
Nucleus Retroambiguus
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
____________ 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
The apneustic center is located in the _______.
Lower pons
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?
- Low PO2
- K+ Channels to close
- Cell depolarizes
- Ca2+ channels open and Ca2+ enters
- Exocytosis of dopamine-containing vesicles
- 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.
1
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
