W11- Lecture 55- Central control of Respiration Flashcards
where is respiration controlled ?
in the medulla oblongata of the brain.
what sets the basic rhythm of respiration ?
medullary neurones
describe the inspiratory centre
where do these signals go + via what
2 dorsally situated regions of the medulla oblongata
centres show a spontaneous rhythmicity and have a cyclic form of activity that arises every few seconds
Action potentials derived from these cells pass along the intercostal nerves and the phrenic nerve to the muscles of inspiration.
describe the expiratory centre
of 2 groups of neurones, these are situated more ventrally either side of the medulla oblongata - Mostly inactive, but during heavy breathing, they send action potentials to the muscles associated with expiration
describe the apneustic centre
where do these signals go
The apneustic centre consists of scattered neurones in the pons. These cells send action potentials to the inspiratory centre.
describe the pneumotaxic centre
This centre consists of a group of neurones in the superior region of the pons. These have an inhibitory effect on the inspiratory and apneustic centres.
describe the impact of the apneustic centre and the pneumotaxic centre on breathing.
the apneustic centre
activates inspiratory centre
the inspiratory centre activates the pneumotaxic centre
the pneumotaxic centre inhibits the apneustic centre
which leads to the inspiratory centre not being activated
what is the Hering Breuer reflex
when is it activated ?
where do the action potentials travel via ?
to where ?
what do these signals do ?
what happens when this is not happening
control mechanism is associated with stretch receptors in the walls of the bronchi.
These are activated during inspiration and send action potentials via the vagus nerve to the medulla oblongata
The action potentials inhibit the inspiratory centres and allow expiration.
During expiration the stretch receptors are inactivated , which in turn allow activation of the inspiratory centres.
what are the two types of receptors ?
where do you find These
how are they connected to the respiratory centres ?
what are they sensitive to ?
the central chemoreceptors and the peripheral chemoreceptors.
The central chemoreceptors are located in the medulla oblongata in the chemosensitive area where they influence the respiratory centres
The peripheral chemoreceptors are located in the carotid bodies and the aortic bodies,
carotid bodies to resp centre via glossopharyngeal nerve
aortic bodies to resp centre via the vagus nerve
changes in the concentrations of hydrogen ions (pH) and oxygen.
how does CO2 effect resp rate ?
how is it detected ?
more co2 lower ph - deeper and quicker breathing
The cheporeseptive area in the medulla is detects changes in blood pH indirectly.
Carbon dioxide concentration of the blood is not directly detected by the chemoreceptors, instead the chemoreceptors detect changes in the bloods pH.
Chemoreceptors in the carotid and aortic bodies detect blood pH directly.
how does ph effect resp rate
lower ph =higher resp rate
higher ph = lower resp rate
what is the percentage ratio of control of the peripheral control vs central in respect to ph
medulla is 80% of total response to pH changes,
peripheral receptors about 20% of the total response to variations in pH.
what is the effect of 02 conc on resp rate ?
where is this detected ?
does it have a large effect/ how much change in conc before change
why /
less 02= more resp rate
detected by the chemoreceptors in the carotid and aortic bodies.
the PO2 has to drop to about 50% of its normal value before blood O2 concentrations have a large stimulatory effect on respiration.
why-This is largely because haemoglobin is virtually saturated with O2 at PO2 of 80mm.
