week 9- control of gas ventilation Flashcards
name the primary sensory receptor
chemoreceptors
what are chemoreceptors sensitive to
co2 changes
o2 changes
where are chemoreceptors found
aortic arch
carotid arteries
medulla oblongata
where do respiratory centres also receive their information from (other sensory inputs)
proprioceptors
cerebral cortex
hypothalamus
lungs-stretch and irritant receptors
Function of Ventral respiratory group
Sets basic rhythm at rest- tidal volume
Where does Ventral respiratory group out put
Phrenic nerve
Intercostal nerve
Function of Dorsal respiratory group
Integrates receptor information and modifies VRG
Function of pontine respiratory centres
Fine tunes breathing rhythm.
Smooths out normal breathing and modifies during activity
E.g. talking, sleep
What occurs In external respiration
Exchange of O2 and CO2 between alveoli and blood in pulmonary capillaries
Explain what occurs internal respiration
Exchange of O2 and CO2 between cells in tisssues and systenuic capillaries
Describe Daltons Law
The total pressure in a mixture of gases is the sum pressure of the individual gases. The pressure of each gas in a mixture is known as the partial pressure
What is the total pressure in a mixture
The sum of the pressure of the individual gases
Describe partial pressure
Pressure of each gas in a mixture
What can influence the shape of haemaglobin
Pao2, Paco2, temperature, blood ph
Describe a hb molecule
-4 globin protein linked together
-each globin protein forms a haem group with an Fe2+
-Fe2+ binds to oxygen it become Fe3+
-each hb can carry 4 o2 molecules
When does hb shape change
When o2 bind
Describe hb in a low o2 state
-molecule is TENSE
-crevice for 02 to move through is small
-o2 affinity is low
Describe hb in a high o2 state
-RELAXED molecule
-crevice for o2 to bind is large
-o2 affinity is high
How does the addition of each o2 molecule effect hb
-each time an o2 bind, hb becomes more RELAXED position
-called CO-OPERATIVE BINDING
Why is the hb graph (PaO2, Percent o2) ‘S’ shaped?
CO-OPERATIVE BINDING
The addition of an O2 molecule changes hb shape to help the binding of the next molecule
-at top of graph, curve flattens as all o2 binding sites are taken. Low o2 affinity. Releases o2 where o2 levels are low
-high o2 levels, affinity of o2 binding increases , reloading takes place
When is the affinity for o2 low
When o2 levels are low (in tissues)
How saturated does venous blood return from the body
75% at rest
1 binding site is used
What offers protection to a loss of ventilation
-o2 is around 13.3kpa in alveoli
-Hb is nearly fully saturated at 10.6kpa
-offer protection to a ventilation loss
How would normal saturations lower than 90-% effect the hb graph
Graph is steeper
Potentials for large desaturation to small o2 changes in body
What other factor effects the way hb carrieso2
- H+ from CO2 binds with globin molecules and promotes TENSE SHAPE
what carries co2 in the blood
-bicarbonate (70%)
-bound toHb(23%)
-dissolved in plasma (7%)
Describe gas transport of co2 from tissues to lungs
-co2 moves down conc gradient into plasma of blood
-co2 moves down conc gradient to rbc where it binds with water
-water and co2 for a weak acid called CARBONIC ACID
-carbonic acid DISSOCIATES into BICARBONATE and H ions.
-bicarbonate diffuse out rbc to plasma
-H + bind to proteins of rbc and promotes TENSE STATE and release of O2
Describe has transport of CO2 from RBC to the lungs
-BICARBONATE ions diffuse back to RBC
-Bicarbonste and H+ ions re-join to form CARBONIC ACID
-carbonic acid DISSOCIATES into co2 and water and H+
-CO2 move down conc gradient to plasma
-co2 diffuses down partial pressure gradient into alveoli where it is ventilated into outside air
-reduces partial pressure of co2 in the lung as sets up gradient that starts the process
describe what happens to co2 and o2 when you hold ur breath
co2 rise
o2 fall
how are o2 and co2 monitored in blood
chemoreceptors in aortic branch, carotid artery and medulla monitor levels of o2 and co2 (H+ ions)
why are u unable to hold your breath indefinitely
chemoreceptors are stimulated by rising co2 and signal DORSAL RESPIRATORY GROUP in respiratory centres of medulla oblongata
DRG has conscious input from cerebral cortex which inhibits normal breathing control during breathing. frequency of AP increase as co2 increases, vertebral cortex is over ridden and DRG eventually send signals to VRG to increase breathing rate and depth to respiratory muscle of breathing (diaphragm, external)
what is breath holding activities i.e. singing, talking controlled by
pneumotaxic/pontine respiratory group
how is blood normally around ph 7
H+ ions during transit of CO2 tpo the lungs is buffered by the non bicarbonate buffering system, mainly Hb, preventing reduction in PH. as the amount of ventilated CO2 matches rate of production the partial pressure of co2 remains constant
how is blood ph 7 when exercising
co2 increases massiveley. chemoreceptors are sensitive to both changes in partoial pressure of CO2 and level of free H+ ions, ventilation is increased to match rate of production.
how does blood ph fall with ventilation failure
co2 is unable to be removed from blood as a direct result of this limitation in ventillation. it accumulates in blood rising and partial pressure of co2 rises.
CO2 + H20 > H2C03 + H+
equation moves right and more H+ made, more acidic
why is oxygen carraige expressed as percentage saturation (SpO2%)
it is carried by HB there are a finite number of carrying molecules and finite amount of o2 carrying ability. total number of occupied binding istes can be expressed as a percentage
define relaxed and tense hb states
decsribe cooperative binding in Hb
binding of o2 facilitates further binding for o2 molecules and vice versa. in the lungs where o2 is high, binding of one o2 molecule to one binding site promotes relaxed states in other binding sites, making binding of the next oxygen molecule easier. in low o2 areas (respiring tissues), o2 is lost promoting the tense states in other binding sites, reducing its affinity for o2, promoting its release to these tissues.
rbc pass through well ventoilated alveoli..
relaxed
rbc pass through muscle during high aerobic exercise…
tense
