Respiratory - Control of Ventilation Flashcards
Respiration demonstrates both:
Automaticity
Self - Modulation
Respiration Automaticity
Begins at birth
automatic
Respiration Self-modulation allows us to:
Voluntarily hyperventilate
Hold our breath
Change breathing patterns for speech and singing
We can override automaticity - voluntary
Ventilatory Control System:
Sensors (chemoreceptors and mechanoreceptors, feedback)
Central Controller (respiratory control center, driver)
Effectors (respiratory muscles, carry out orders)
Neural Control of Breathing: Voluntary
What controls it?
Cerebral Cortex
Neural Control of Breathing: Autonomic
What controls it?
Medullary Centers
Pontine Centers
Respiratory Centers
What makes up the medullary respiratory centers?
Dorsal Respiratory Group
Ventral Respiratory Group
What makes up the Pontine Respiratory Centers?
Pneumotaxic Center
Apneustic Center
Which respiratory control center does majority of the work?
Medullary centers
Dorsal Respiratory Group (DRG)
What is it? What makes it up?
Comprised mainly of inspiratory neurons
responsible for inspiration
Influences Pre-Btzinger Complex
Pre-Botzinger Complex
The anatomic location of the respiratory pattern generator
these neurons display pacemaker activity
Ventral Respiratory Group (VRG)
Responsible for both expiration and inspiration, but inactive during quiet breathing
active during exercise
Pontine Centers
What is it? What does it do?
Rhythm generated in the medulla can be modified by neurons in the pons
Fine tune breathing
What happens if the spinal cord is cut between the medulla and the pons?
Fairly normal ventilation
What happens if the spinal cord is cut below the medulla?
Ventilation ceases
What is the major rhythm generator?
Medulla
Neural Control
Sensors
What do they do?
Reflexes from the periphery provide feedback for fine-tuning
Define
Mechanoreceptors
Type of Sensor
Detect distention and irritation
Airways, Lung parenchyma
Define
Chemoreceptors
Type of Sensor
Chemical content of blood or CSF
Samples levels of PO2, PCO2, H+
Where are central chemoreceptors located?
In brain
Located on surface of medulla; seperate from respiratory center
What is the most important mechanism controlling ventilation at rest?
CO2-Induced H+ in CSF
Does CO2 directly bind chemoeceptors?
No
What causes a loss of sensitivity to elecated PaCO2 during prolonnged hypoventilation?
Chronic Lung Disease
Loss of sensnitivity to PaCO2
HCO3- gets actively transspirted to BBB
Central chemoreceptors no longer “aware” of elevated PCO2
Hypoxic drive becaomes primary respiratory stimulus
Should we administer O2 when a patient’s primary respiratory stimulus relies on CO2?
No
Adapts
Do central chemoreceptors respond to hypoxia?
No
Peripheral Chemoreceptors
Outside brain
Glomus cells in the carotid and aortic bodies that detect O2, CO2, and H+
Peripheral Chemoreceptors
Hypoxia
What does it do to PaO2?
Respond to PaO2 not oxygen content
Normal = no response
Inhibit K+ channels; depolrize cell
Stimulates chemoreceptors to increase ventilation; impt emergency mech
Peripheral CHemoreceptors
Hypercapnia
Central receptors more sensitve
CO2 diffuses into glmus
H+ inhibits K+ Channel
Peripheral Chemoreceptors
Acidosis
Arterial H+ inhibits K+ channel
What is the effect of dangerously low PaO2 on peripheral chemoreceptors?
The activity of all other nervous tissue becomes reduced with O2 deprivation
If not for stimulatory effect on peripheral chemoreceptors, ventilation would cease
Effect of Increased PaCO2 on Ventilation
Arterial PCO2
The most important regulator of ventilation
response primarily arises from central chemoreceptors with added input from peripheral chemoreceptors
Effect of Increased PaO2 on Ventilation
Arterial PO2
What happens when it is low?
When PO2 is low, ventilation increases
response from peripheral chemorepectors (central do not directly sense PO2)
Effect of increased H+ on ventilation
Arterial pH
As H+ increases, ventilation increases
H+ cannot diffuse into CSF as well as CO2
Pulmonary Stretch Receptors
Mechanoreceptors in smooth muscle of conducting airways
Respond to lung distention
Excited inspiratory off switch
Shortend inspiration
Point and Muscle Receptors
Mechanoreceptors in joints and muscles signal to DRG to increase breathing frequency
Activated during movement when O2 demand will remain high
Increase ventilation immediatly after, have yelling matdches at school
Irritant Receptors
Mechanoreceptors in airway epithelium of larger conducting airways
Respond to irritation of the airways by touch, dust, and smokeo
Protects by inducing a cough and hypercapnea
Juxtapulmonary Capillary Receptors (J receptors)
Stimulated by distortion
Increase ventilation
Why is countercurrent multiplication important?
Brings water into system
