Exam #3: Control of Breathing Flashcards
How is spontaneous respiration produced?
Rhythmic discharge of motor neurons that innervate respiratory muscles
What controls the discharge of the motor neurons responsible for respiration?
Chemical control:
- PCO2
- PO2
- H+
Where is the automatic control of respiration located?
Pons & medulla
Where is the voluntary control system of respiration located?
Cerebral cortex
What are the key controlling factors of respiration?
Increased PCO2*
Decreased PO2
Decreased pH
Draw the pathways that control breathing.
N/A
What are the non-chemical influences that control breathing?
Chest wall
Diaphragm
Conducting airway
Changes here sends signals directly to the spinal cord to alter breathing e.g. during exercise
What is the most important controlling factor of respiration?
Changes in PCO2
*Stronger effect than changes in pH
Can the partial pressure of oxygen change the respiratory rate independent of CO2?
Yes
In what range is the chemoreceptor system the most sensitive to changes in PO2?
30 - 60 mmHg
How does the effect of PCO2 & H+ compare in the control of respiration?
Changes in blood H+ have considerably less effect in stimulating chemosensitive neurons
Where are the peripheral chemoreceptors that detect changes in PO2?
Aorctic bodies
Carotid bodies
*Note that these respond to changes in CO2 & H+ to a lesser extent than oxygen
Where are the central respiratory chemoreceptors located?
In a “chemosensitive area” that lies just beneath the medulla
3 regions:
1) Rostral (Mitchell)
2) Intermediate (Schlafke)
3) Caudal (Loeschcke)
Where is the sensory integration center for impulses from peripheral chemoreceptors, baroreceptors, & other pulmonary receptors.
NTS
What are the four nuclei of the respiratory center?
1) DRG= Dorsal Respiratory Group
2) VRG= Ventral Respiratory Group
3) PRG= Pneumotaxic Respiratory Group
4) Pre-Botzinger complex
What is the function of the Pre-Botzinger complex?
Rhythmic respiration
*Note this is like the SA node in the heart.
Where do signals from the Pre-Botzinger complex go?
DRG
What is the function of the DRG?
Sends out repetitive bursts of inspiratory neuronal action potentials
What is the function of the PRG?
- Transmits signals to the inspiratory area (DRG)
- Switches off the DRG
*Primarily controls rate & depth of breathing
What is the function of the VRG?
- Inactive during normal respiration
- Increased stimulation results in spill over from the DRG
- DRG spillover recruits the VRG for active breathing (both inspiration & expiration)
How is respiration regulated during exercise?
Voluntary component added to the automatic component
What are irritant receptors?
Receptors that are stimulated to edema, toxic substances, smoking…etc.
What is the function of irritant receptors?
Causing coughing & sneezing
Note that these may also cause bronchial constriction in asthma & emphysema
What are J receptors?
Sensory nerves located in the alveolar walls, in juxtaposition to the pulmonary capillaries
What stimulates J receptors?
- Pulmonary capillary engorgement or pulmonary edema
- Gives a feeling of dyspnea
What is the effect of brain edema on respiration? How is it treated?
- Depressed respiration
- Hypertonic solutions e.g. mannitol
What reflex is initiated by the stretch receptors?
Hering-Breuer inflation reflex
- Located in the muscular portions of the bronchi & bronchioles
- Transmits signals to the DRG when the lungs are overstretched
- Switch off inspiratory ramp & increases the rate of respiration
Note that this normally does not happen until VT= 3x normal
What is the Hering-Breuer inflation reflex?
- Switch off inspiratory ramp in cases of overstretching of the lung parenchyma
What are Kussmaul’s respiration’s an indication of?
Metabolic acidosis
- Relentless, rapid, & deep breathing
What are Cheyne-Stoke’s respiration’s an indication of?
Stroke
Encephalopathies
Heart Failure
Ventilatory oscillations with long cycle times
What is Biot’s breathing an indication of?
Medullary trauma
Stroke
- Quick, shallow inspirations followed by regular or irregular periods of apnea
Draw the diagrams of Kussmaul’s, Cheyne-Stokes, & Biot breathing patterns.
N/A
Describe the reciprocal innervation of the respiratory muscles.
Active inspiratory muscles= inhibited expiratory muscles & vice versa
What do the central chemoreceptors respond most to? What do the peripheral chemoreceptors respond most to?
PCO2 & PO2 respectively
