Control Of Breathing Flashcards
(21 cards)
What is normal minute ventilation at rest
5L/min
What is max voluntary ventilation (MVV)?
Maximum air ventilation
125-175 L/min
Greater in men and athletes
Normal range for Arterial pH?
7.35-7.45
Range for arterial PO2?
81-100mmHg
Range for arterial PCO2?
35-45mmHg
Partial pressure of O2 in the air?
150mmHg
Barometric pressure (PB) =760mmHg
Percentage of O2 in air (FO2) =0.21
0.21 x 760 =160 mmHg
However must minus water Vapor pressure (47mmHg) from PB meaning new equation is 0.21 x 715 =150 mmHg
Describe the hemoglobin dissociation curve?
Pressure of O2 in the blood and haemoglobin saturation.
How does the hemoglobin dissociation curve affect O2 use?
At high partial pressure seen at sea level haemoglobin readily binds to O2 from alveoli
Pressure gradient of atmosphere must be higher than gradient of mixed venous blood (40mmHg) to ensure efficient diffusion of O2 from alveoli to hemoglobin
Where are central chemoreceptors?
Brain stem
Respiratory control system
Central controllers (pons, medulla)
Sends signals to effectors
Effectors (resp muscles)
Sensors (chemoreceptors)
Sends signal to central control
What is the role of the Pons
Modified output of medullary centres
Role of medula oblongata
Controls rhythmic cycle of breathing
Two dense bilateral groups of neurons
Dorsal respiratory groups (DRG) sends signals to diaphragm/resp muscles. Sends signals to lungs vagus/glosopharyngeal nerve
Ventral respiratory groups(VRG) contains insp and exp neurons
What do central chemoreceptors respond to?
Drop in pH of Cerebral spinal fluid (CSF)
How does pH of CSF drop?
CO2 diffuses of blood brain barrier
Normal pH of CSF
7.32
What happens if central chemoreceptors are cooled?
Stop firing
Do chemoreceptors respond to change in CO2 or pH?
Both
Where are peripheral chemoreceptors
Carotid bodies (carotid sinus)
Aortic arch
What do peripheral chemoreceptors respond to?
Drop in partial pressure of O2
As well as increase in CO2 and decrease pH
Conditions for peripheral chemoreceptors to work?
Extremely low levels O2, as peripheral chemoreceptors work only as backup to central chemoreceptors
What happens if low levels O2 are quickly returned to high levels of O2
Drive to breathe lost
As peripheral chemoreceptors increase drive to breathe and expel CO2 to low levels making central chemoreceptors redundant.
Large increase in O2 stops peripheral chemoreceptors firing in addition to central chemoreceptors already not firing.
