Steps of respiratory controls
- Medullary center
- Effectors
- Controlled variable
- Sensor
Apneusis
failure to turn inspiration off
-can occur when the PRG is lesioned (if there is not additional sensory information coming from the vagus nerves)
What determines the timing of respiration?
- PRG (pons): modifies inspiratory timing (activity–> turns off inspiration)
- *Pre-Bot (medullary): generates core pattern
*the younger you are, the more important it is
What determines depth of respiration?
- DRG (medullary): 95% premotor to phrenic; receives sensory information to help it determine pattern based on situation–> deep breathing (tidal volume)
- VRG (medullary): 2 parts
a. Rostral: premotor to phrenic, other inspiratory m.s
b. Caudal: premotor to upper airway, other expiratory m.s
Apneusis vs. Apnea
- Appearance
- Results from
- Effects
- Maintained inspiratory discharge
- absence of respiratory effort - Pontine damage
- medullary or spinal damage - Slight delay, but then increase CO2, decrease O2, death if not supported
- increase CO2, decrease O2, death if not supported
What is a chemoreceptor?
A neuron that is sensitive to specific chemicals
-in the respiratory system, these signals are: O2, CO2, H+
- Increase CO2/H+: increased firing
- Decrease O2: increased firing
Where do we find central chemoreceptors? peripheral?
a. brain (ventral surface of the medulla)
b. carotid and aorta
Central chemoreceptors
- indirectly sensitive to CO2 in the blood; directly with H+ (pH of CSF)
- CO2 (indirect) crosses BBB to react with water, which forms H+ (direct)
- drive to breath
- increase respiration/depth in response to hypercapnia
Peripheral chemoreceptors
- directly sensitive to O2, CO2, H+
- aortic arch uses different nerves than the carotid body, and serves as a back-up
- acute changes in blood gas
- -increase respiration/depth in response to hypercapnia , acidosis, and hypoxia
Ve=
f x Vt
Slowly Adapting Pulmonary Stretch Receptors
- located in airways; fibers travel to brain with Vagus N.
- sensitive to stretch of airways
- effect: inhibition of inspiration, and prolongation of expiration
- want to decrease lung volume; important in infants, and exercising adults
Rapidly Adapting Pulmonary Stretch Receptors
- located in airways; fibers travel to brain with Vagus N.
- sensitive to irritation, foreign bodies in airway, stretch
- effect: cough to remove irritant
Juxtacapillary Receptors
- located near BVs of alveoli; fibers travel to brain with Vagus N.
- sensitive to pulmonary edema
- Effect: cough, tachypnea
What two receptors can override normal respiratory controls?
Juxtacapillary Receptors and Rapidly Adapting Pulmonary Stretch Receptors
Cortical influence on breathing
- talking, holding breath…
- cortex can bypass the medullary centers completely, and send input directly to the muscles of respiration
