L3-central control of respiration Flashcards
what is respiration controlled by?
mostly controlled by nerve cells or neurones in the medulla oblongata of the brain
what influences the rhythm of respiration
the medullary neurones set the basic rhythm but the rhythm can be influenced by inputs from other part of brain and peripheral sensory receptors
where is the respiratory centre (RC) located
medulla oblongata
2 regions of the RC
inspiratory centre
expiratory centre
what does the inspiratory centre consist of?
2 dorsally situated regions of medulla oblongata
how does the inspiratory centre function
the neutrons show spontaneous rhythmicity
cyclic form of activity rises every few seconds
the activity sets basic rhythm of respiration
action potential derived from these cells pass along the intercostal nerves and phrenic nerve to muscle of inspiration
what does the expiratory centre consist of
consists of 2 groups of neurones
situated more ventrally either side of the medulla oblongata
function of the expiratory centre
mostly inactive
during heavy breathing
send action potentials to the muscles associated with expiration
what is hering breuer reflex
control mechanism associated with stretch receptors in the walls of the bronchi
when is hering breur reflex activated
activated during inspiration and send action potentials via the vagus nerve to the medulla oblongata
what does action potential inhibit in HB reflex
action potentials inhibit the inspiratory centres and allow expiration
how are the HB reflex inactivated
during expiration the stretch receptors are inactivated which in turn allow activation of the inspiratory centres
how is the chemical control of respiration achieved
central and peripheral chemoreceptors
where are central chemoreceptors located
located in the medulla oblongata in the chemosensitive area where they influence the respiratory centres
where are the peripheral chemoreceptors located
located in the carotid bodies and these connect to the respiratory centres by glossopharyngeal nerve and the vagus nerve respectively
chemoreceptor respond to change in what
respond to changes in the concentration of hydrogen ions (pH) and oxygen
what is hypercapnia
an excessive PCO2 in the blood
what is hypocapnia
lower than average PCO2
is carbon dioxide concentration of blood directly detected
no it is not directly detected by the chemoreceptors instead the chemoreceptors detect changes in the bloods pH
how is the pH detected by the chemoreceptors
pH is detected by the chemorecptive area in the medulla oblongata and by the peripheral chemorecptors
what detects changes in blood pH directly
the chemoreceptive area in the medulla
what detects blood pH directly
chemoreceptors in the carotid and aortic bodies
effect of pH on respiratory rate
decreases in pH result in an increase in the respiratory rate
increase in pH results in a decrease in the respiratory rate
what is the chemosensitive area of the medulla responsible for
80% of total response to pH change
what are the peripheral receptors responsible for
20% of the total response to variations in pH
what detects the oxygen concentration in the blood
chemoreceptors in the carotid and aortic bodies
what happens if PCO2 remains constant
the PO2 has to drop to about 50% of its normal value before blood O2 concentrations have a large stimulatory affect on respiration
what is haemoglobin saturated with
virtually saturated with O2 at PO2 of 80mm
what needs to happen in order for increase in respiratory rate to be triggered
PO2 levels have to drop significantly in the aorta and the carotid arteries before the low O2 concentration triggers an increase in the respiratory rate
