respiratory physiology 2 Flashcards
ventilation control
inspiration is aided by muscles that are stimulated by the intercostal nerves an dthe phrenic nerve.
expiration is a passive process
factors that stimulate the respiratory centres in the brain
emotion that is via limbic system in the brain.
voluntary over -ride that is through higher centres in the brain.( example is cerebral cortex)
mechanosensory input form the thorax that is the stretch reflex.
chemical composition of the blood that is pco2 and po2 and pH
dorsal respiratory group of muscles
they control the inspiratory muscles that is through the phrenic and the intercostal nerves .
ventral respiratory group of neurons
that is the toup , pharynx , larynx and the expiratory muscles ( that is the internal intercostal muscles )
chemoreceptors in the brain
central chemoreceptors and peripheral chemoreceptors
examples of central chemoreceptors
medulla - that measure strictly the amount of hydrogen ions in the CSF which is as a result of carbon dioxide since carbon dioxide is a gas it can pass through the blood brain barrier.
primary ventilatory drive
central chemoreceptors
secondary ventilatory drive
peripheral chemoreceptors
peripheral chemoreceptors
carotid and aortic bodies
they respond to both PO2 ( primarily ) and PCO2 in the plasma .
in this case the hydrogen ions are not an accurate measure as they could be from anything else that is not failure of the respiratory system.
central chemoreceptors in the medulla
the receptors detect changes in hydrogen ions in the CSF and causes reflex stimulation of ventilation following the rise in hydrogen ions
decrease of hydrogen ions in the CSF
leads to a decrease in the rate of ventilation
( there is less carbon dioxide )
chronic lung disease and paCO2
with chronic lung disease there is always elevated levels of carbon dioxide ; they become desensitised to the increased levels in the carbon dioxide they therefore rely on oxygen pressure
hypoxic drive
reliant of oxygen for ventilation control
peripheral chemoreceptors
they are the carotid and aortic bodies
carotid and aortic bodies
changes in the arterial PO2 and Hydrogen ions
peripheral chemoreceptors
they cause reflex stimulation of ventilation following significant fall in arterial PO2
changes in oxygen partial pressure
changes upto 60 can lead to the changes in ventilation
what does the peripheral chemoreceptors detect
Respond to arterial PO2 not oxygen content
anaesthesia and ventilatory control
Most gaseous anaesthetic agents increase RR but decrease TV so decrease AV.
opioids and barbiturates
an overdose results in a decrease to the sensitivity of pH and therefore response to pCO2 .
nitrous oxide
common sedative/light anaesthetic agent, blunts peripheral chemoreceptor response to falling PaO2. Very safe in most individuals, problematic in chronic lung disease cases where individual often on “hypoxic drive”. Administering O2 to these patients aggravates situation.
how changes in plasma alter ventilation via the peripheral chemoreceptor pathways
if plasma pH falls ventilation will be stimulated
if plasma ph increases there will be decreased ventilation
hypoventilation
Hypoventilation, causing CO2 retention, leads to increased [H+] bringing about respiratory acidosis.
hyperventilation
Hyperventilation, blowing off more CO2, lead to decreased [H+] bringing about respiratory alkalosis
important chemical equation
pH is directly proportional to the bicarbonate ions
pH is indirectly proportional to carbon dioxide produced
ventilation during exercise
ventilation occurs more than metabolism the arterial hydrogen ions will increase because of the increase in the lactic acid concentration hence the hyperventilation
