The ultimate goal of respiration is to maintain proper concentrations of __________________ in the tissues.
O2
CO2
H+
Excess CO2 or H+ activates respiratory centers to _________ alveolar ventilation.
increase
Decreased O2 _________ alveolar ventilation.
increases
What is detected by peripheral and central chemoreceptors?
high CO2
high H+
What is detected by peripheral chemoreceptors?
low O2
What are the two basic controls of breathing?
voluntary (corticospinal tract)
automatic (ventrolateral tract)
What does the voluntary/corticospinal tract involve?
descending input from the thalamus and cerebral cortex, can bypass the respiratory control centers in pons & medulla
When is the voluntary/corticospinal tract active?
talking, sneezing, singing, swallowing, coughing, defecation, anxiety, fear
What is the automatic/ventrolateral tract controlled by?
– Primarily controlled by changes in PCO2
* Less sensitive to PO2 and H+
* Pulmonary mechanical receptors
When is the automatic/ventrolateral tract activated?
Respiratory Centers in the pons & medulla (ex. DRG and VRG)
What are the two areas of the brainstem that control respiration?
medullary respiratory center
pontine respiratoyr group
What are the two sections of the medullary respiratory center?
– Dorsal Respiratory Group (DRG; inspiration)
– Ventral Respiratory Group (VRG; active expiration and inspiration)
What are the two sections of the pontine respiratory group?
– Pneumotaxic Center
– Apneustic Center
What is the dorsal respiratory group (DRG)?
- nucleus of the tractus solitarius
- inspiratory center
- one of the medullary respiration centers
What does the DRG receive afferent input from?
CN IX (chemoreceptor)
CN X (chemoreceptor and mechanoreceptor)
What does the DRG mirror the activity of?
the diaphragm
How does the DRG provide excitatory inspiratory stimuli to phrenic motor neurons?
- Sets the basic rhythm for breathing by setting the frequency of inspiration—Central Pattern Generator
- Signal begins weakly, increases steadily for 2 seconds, then will abruptly cease for ~3 seconds before resuming the cycle (12-20 breaths per minute
DRG contains opiate receptors (u receptors) that, when activated,
______ respiration
inhibit
Which medullary respiratory center is mostly involved in expiration?
VRG
VRG is the control for the motor neurons in the…
- Expiratory muscles (abdominals, internal intercostals)
- Accessory inspiratory muscles
What is the pneumotaxic center?
- When activated, shortens the time of inspiration (possibly by inhibiting the Apneustic Center).
- Might inhibit the Apneustic Center.
- decrease tital volume
What is the apneustic center?
- Its activation causes excitation of
the DRG which results in prolonged
inspiration with brief periods of
expiration. - Antagonist to Pneumotaxic Center
- increase tital volume
What is the Hering-Breuer Reflex?
Stretch receptors in bronchi and bronchioles are activated when the lungs over-stretch
How do you activate the Hering-Breuer reflex?
Stops further inspiration and decreases rate.
