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»Chemical Control
» Respiration is controlled by chemoreceptors
that are sensitive to chemicals dissolved in body
fluids.
» Chemoreceptors are located centrally near the
brain stem and peripherally in the arteries.
» Central Chemoreceptors
» These receptors can be found on either side of
the brain stem near the medulla oblongata
» It responds to CO2 levels circulating in the
blood and to the Hydrogen ions as the CO2 is
converted into bicarbonate and H+ (sensitive to
the change in pH)
» Hypercapnia is the rise in blood CO2 levels and
this triggers ventilation
» Peripheral Chemoreceptors
» These structures are not found in the brain but
are located in the carotid and aortic arch.
» These contain sensory neurons that respond
mainly to a decrease in oxygen supply
» They are not usually involved in regulating
breathing because they do not act until oxygen
drops to a very low level.
» Ultimately, carbon dioxide then has the most
immediate effect in regulating respiration.
» When carbon dioxide levels increase, breathing
must be increased to blow off the excess gas
» Hyperventilation
» This condition results from deep and rapid
respiration that commonly occurs during
anxiety attacks, or when a person is
experiencing pain or other forms of stress
» Hyperventilation causes an increase in the
oxygen levels and a decrease in carbon dioxide
levels
» This low level of carbon dioxide changes the pH
of the blood which causes dizziness and tingling
sensations
» In extreme cases, a person may faint and then
breathing will involuntarily return to normal
» To help a person who is hyperventilating, speak
calmly and reassuringly and encourage them to
take even breaths from the diaphragm
» Hypoventilation
» Caused by insufficient amounts of air entering
into the alveoli.
» Causes can include:
˃
˃
˃
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Respiratory obstruction
Lung disease
Injury to the respiratory center
Depression of the respiratory center(caused by
drugs)
˃ Chest deformity
» Read A Closer Look on pg 415
» Adaptations to High Altitude:
Living with Hypoxia and complete
the questions in your notes
booklet