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Respiratory Control

Terms in this set (34)

How does our body maintain homeostatic variables (pCO2 and pO2)?
through control of alveolar ventilation
Explain the mechanisms behind inspiration.
Feedback from lung mechanoreceptors carried in the vagal n terminates the phrenic n stimulation of inspiratory muscles

the medulla initiates inspiration and the lung stretch ends inspiration
What are the four major sites of ventilatory control?
1. respiratory control center
2. central chemoreceptors
3. peripheral chemoreceptors
4. pulmonary mechanoreceptors/sensory nerves
Where is the respiratory control center located? What is it composed of?
the medulla oblongata

composed of multiple nuclei that generate and modify the basic ventilatory rhythm
What are the two parts of the respiratory center?
1. a ventilatory pattern generator - sets the rhythmic pattern
2. an integrator - controls generation of the pattern
Where does input to the integrator arise from?
higher brain centers
- cerebral cortex
- hypothalamus
- limbic system including the amygdala and cerebellum
What are the afferent inputs? What are the efferent inputs?
Afferent:
- peripheral chemoreceptors
- central chemoreceptors
- lung stretch receptors
- muscle and joint receptors

Efferent:
- diaphragm
What is their main goal?
to maintain the steady state
Negative Feedback Control of Respiration: What is the sensor?
the peripheral and central chemoreceptors
Negative Feedback Control of Respiration: What is the comparator?
the CNS
- pons
- medulla
- cortex
Negative Feedback Control of Respiration: What is the error signal?
medulla
Negative Feedback Control of Respiration: What is the physiological response?
motor nerves in the diaphragm and intercostals respond to ventilation

To decrease:
- increase H+
- increase PO2
- decrease PCO2

To increase
- increase H+
- decrease PO2
- increase PCO2
What is the dorsal medulla responsible for?
inhalation and airway defense
What is the ventral medulla responsible for?
exhalation
How do the dorsal and ventral medulla communicate?
by integrating input from central and peripheral receptors prior to relaying information to respiratory muscles to generate respiratory rhythm
What does pontine grouping allow for? Why?
modulation of the intensity and frequency of the medullary signals to control breathing patterns while promoting a smooth transition between inspiration and expiration
What coordinates the speed of breathing? How?
the pneumotaxic center in the upper portion of the pons

it sends inhibitory impulses to the respiratory center and is involved in the fine-tuning of respiratory rate
What helps the pons coordinate the speed of breathing?
the apneustic center in the lower portion of the pons

but it can be overridden by the pneumotaxic center to end inhalation

this region is mostly responsible for sending stimulatory impulses to the inspiratory area
What makes up the sensory input systems and what do they do?
mechanoreceptors, metaboreceptors, and peripheral and central chemoreceptors

they coordinate with other components of the respiratory response system to control breathing
Explain the mechanism behind controlling the mechanical aspects of respiration.
Information from neuronal and sensory input systems signals to the diaphragm and other respiratory msucles
What is the depth of inspiration based on?
the level of activity of the respiratory center in the brain and subsequent stimulation of motor neurons
What is responsible for most of the pressure changes during inspiration?
contraction and relaxation of the diaphragm and intercostals
What are the most important muscles for expiration?
abdominal muscles and internal intercostals

they contract and compress the abdominal organs pushing them up into the diaphragm, raising pleural and alveolar pressure, and driving air our of the lungs
What nerve innervates the diaphragm?
phrenic
What act as the pacemaker for the respiratory system and what do they do?
PreBotC and VRG

they generate a respiratory pattern
T/F: There is reciprocal inhibition for inspiration.
True
What is a major regulatory factor in the respiratory system?
CO2
Where are the peripheral chemoreceptors located and what do they do?
aortic arch and carotid body

they respond to hypoxia and hypercapnia
What do the central chemoreceptors respond to during hypercapnia?
the pH of the CSF

CO2 will then diffuse across the BBB and initiate a response (mostly H+)
What are some respiratory patterns?
Cheyne-Stokes respiration = cyclic pattern of alternating hyperpnea and apnea; may indicate incipient transtentorial herniation

Hyperventilation = injury of the pontine or midbrain

Apneustic breathing = prolonged pause at the end of inspiration; lateral tegmentum of the lower half of the pons

Cluster breathing = periodic respirations that are irregular in frequency and amplitude with variable pauses between clusters of breaths; lower pontine tegmental lesion

Ataxic breathing = irregular in both rate and tidal volume; suggests damage to the medulla
What occurs with the blood gasses during submaximal exercise?
this is exercise below anaerobic threshold

ventilation increases linearly with CO2, whereas PaCO2 remains relatively constant, indicating that ventilation matches the increasing metabolic rate
What occurs with the blood gasses during heavy exercise?
this is exercise above anaerobic threshold

ventilation increases somewhat more than CO2, and consequently PaCO2 decreases
Explain the phases of ventilation response to exercise.
Phase 1 = an immediate increase in ventilation at exercise onset

Phase 2 = an exponential increase in ventilation (slow component) until

Phase 3 = steady state
Explain the different pulmonary stretch receptors.
C-Fiber Receptors = a rich network of small, unmyelinated axons with nerve endings - juxtacapillary or J receptors - in alveoli and conducting airways

Sigh or "Augmented Breathing" = a sigh is a slow and deep inspiration, held for just a moment, followed by a longer-than-normal expiratory period.

Yawn = an exaggerated sigh, a yawn takes lung volume to total lung capacity for several seconds

Cough reflex = coughing is important for ridding the tracheobronchial tree of inhaled foreign substances. There is probably no single class of "cough receptors".

Sneeze = sensors in the nose detect irritants and can evoke a sneeze. Curiously, these same receptors are probably also responsible for apnea in response to water applied to the face or nose, which is part of the diving reflex that evolved in diving mammals.
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