Regulation of Respiration Flashcards
what is the mechanism of control of respiration? what is the feedback?
- the medulla in the brain stem has neurons that project signals to the spinal cord motor neurons
- the spinal and thoracic motor neurons continue into the phrenic nerve for diaphragm control or motor neurons of intercostal muscles
- this contributes motor control over the respiratory muscles and lung
- the lungs rhythm of tidal volume controls alveolar PO2 and PCO2 which is responsible for arterial PO2 and PCO2
- feedback includes chemoreceptors to sense arterial pressures, chemoreceptors in the lung, and muscle spindles in respiratory muscles that signal back to brain stem
what are the motor neurons that control respiration and what exactly do they control?
- phrenic motor neurons (C3-C5) = control diaphragm
- intercostal motor neurons (thoracic spinal cord) = control of muscles of chest wall (intercostal muscles)
- motor neurons of larynx and pharynx (nucleus ambiguus) = control larynx for resp.
what happens during apnea?
no breathing, no movement of chest wall or diaphragm
- lack of neural control
where exactly is the control center for respiration?
between the pons and medulla
what are the medullary respiratory centers and what do they do?
- dorsal respiratory group = nucleus solitarius – neurons that cause inspiration
- ventral respiratory group = nucleus ambiguus – neurons that cause inspiration and expiration
what are the pontine centers and what do they do?
- pneumotaxic center
if you disrupt this region, you also disrupt apneustic center
kinda like the starting part of the signaling - apneustic center = emphasis on inspiration
requires more time
control inspiratory neuron
what is the carotid body and what does it do? what is it innervated by?
- located near the carotid sinus and senses low oxygen levels in the blood for feedback
- if levels are too low, it signals back to the brain that inspiration needs to increase
- innervated by CN IX
how does neural discharge change with oxygen levels?
- neural firing increases to signal for increase inspiration when O2 levels are low
- only when the arterial PO2 drops to 60mmHg or less, the neural discharge increases significantly
how does hypoxia affect ventilation?
- again, hypoxia = low levels of O2 in the blood
- so when you are hypoxic, you increase ventilation to try to compensate and increase O2 levels
- less than 60% = 60mmHg PAO2
what is the mechanism for signaling via the carotid body?
- when the arterial PO2 decreases
- there is an increase in Ca release from Type I glomus cells
- Ca is released and signaled to the glossopharyngeal nerve and a nerve afferents
how does blood flow in the carotid body compare to other tissues in the body?
it has the HIGHEST blood flow per gram of tissue than any other tissue in the body
what do nerve afferents respond to?
- low arterial PO2
- NOT O2 content or saturation but to the partial pressure of O2 in the blood
what is the effect of anemia on ventilation?
= normal O2 but low O2 content bound to Hb
- does not trigger hyperventilation because there is a normal arterial PO2
- only causes hyperventilation is Hb is <3g/dL
what is the effect of CO poisoning on ventilation?
= normal PO2 but CO replaces oxygen binding on Hb
so does not trigger hyperventilation because still have normal oxygen levels but cannot transport it or exchange it
what is the effect of decreased blood flow on ventilation?
causes and increase in neural firing = trigger hyperventilation
- caused by hemorrhagic shock or heart failure
what happens when there is an increase on arterial PCO2 (more CO2 in the blood)?
- triggers hyperventilation just by small increase in arterial PCO2
- chemoreceptors are very sensitive to CO2
what happens with elevation change to pressures?
- as you increase elevation, you decrease barometric pressure
- subsequently, you decrease the pressure of inhaled oxygen in the body
- this results in low O2 pressure in the body (near 0)
