22 19-20 Flashcards
What two areas of the medulla oblongata are critically important to respiration?
DRG - dorsal respiratory group, VRG - ventral respiratory group (in charge) in medulla. Has most control.
DRG
Dorsal respiratory group - near root of cranial nerve IX,
integrates peripheral sensory stretch input and chemoreceptors, and modifies the rhythms generated by VRG (sends signals there). Emotional/temp/pain
VRG
Ventral respiratory group - Pons/medulla to spinal cord,
contains rhythm generators that drive respiration.
A rhythm generating and integration center containing separate group of neurons: Inspiratory and Expiratory.
Inspiratory neurons, via phrenic and intercostal nerves, stimulate contraction of the diaphragm and intercostal muscles.
Expiratory neurons - when they fire, out to the respiratory muscle stops, muscles relax and lungs recoil.
PRG
Pontine respiratory group - Transmits to the VRG to tweak respiration, receives signals from peripheral sensory receptors and higher brain centers.
Has some inspiratory and expiratory neurons as well as mixed neurons which are associated with inspiration/expiration.
For instance, will modify if ya break into song…
Where does input to the respiratory centers come from/factors that influence rate and depth? 6
Hypothalamus - from receptors and limbic/emotional stimuli/pain/temp.
Higher brain centers - conscious control over breathing.
Stretch receptors in the lung - prevent overstretching and when quiet intiate stretch/Hering-Breuer reflex.
Irritant receptors in the the lungs - reflexive bronchoconstriction.
Proprioceptors in muscles and joints - notify of an increase in activity.
Central chemoreceptors - sense levels of ↑CO2, ↑H+.
Peripheral chemoreceptors - sense ↓O2, ↑CO2, ↑H+.
What chemical factors influence breathing rate and depth?
Changing levels of CO2, O2 and H+ in arterial blood.
What receptors monitor CO2, O2 and H+ in blood?
Central chemoreceptors in the medulla oblongata, Peripheral chemoreceptors in the aortic arch and carotid arteries.
How does an increase in Pco2 effect rate and depth of breathing?
Causes an increase.
Increase in arterial Pco2 cause CO2 levels to rise in the cerebrospinal fluid resulting in stimulation of the central chemoreceptors.
Low Pco2 levels depress respiration.
How does a drop in Po2 affect respiration rate and depth?
Substantial drops are required due to the large reserves of O2 carried on hemoglobin.
Causes an increase.
Carotid and Aortic bodies.
How does H+ affect respiration rate and depth?
When H+ accumulates in the plasma, rate/depth increase in an attempt to eliminate carbonic acid from the blood through the loss of CO2 in the lungs.
Changes in arterial pH can affect modify independent of Pco2/Po2.
Peripheral chemoreceptors
Chemical influences on ventilation (table format)
Peripheral chemo/carotid-aortic.
Central chemo/medulla oblongata
↓ Po2 (arterial)
Only work in emergency/Po2 less than 60mmhg
Depresses central chemoreceptors+resp.ctr.
↑ Pco2 (Arterial + H+ in brain ECF)
Weakly stimulated
Dominant factor in ventilation (causes loss of pH in brain)
↑ H+ in arterial blood
Stimulated
No effect (H+ does not cross BBB)
Why is an ↑ in Pco2 the most dominant factor in controlling respiration rate/depth?
Because of loss of pH in the brain.
↑ Pco2 –> brain –> Pco2 in brain ECF –> CO2+H2O –> H2CO3 –> H+ (the culprit) + HCO3-
Co2 accumulates in the brain, is hydrated to form carbonic acid, acid dissociates, H+ is liberated, pH drops.
Why do divers hyperventilate?
To lower Co2 in order to hold their breath longer Danger of this is that because they can hold their breath longer they could suffer from O2 deprivation/Co2 overload and pass out.
Eupnea
Normal respiratory rate and rhythm
Hypercapnia
High levels of CO2 in the blood.
