PBL 2 - control of breathing Flashcards
why do we need to control breathing?
- regulate gas exchange
- execute behavioural acts
- maintain airways and lung function
what is the somatic motor innervation of the pharynx and larynx supplied by?
cranial nerves
- glossopharyngeal (IX)
- vagus (X)
- spinal accessory (XI)
- hypoglossal (XII) (tongue)
what are the pump muscles?
diaphragm, intercostal muscles, abdominal muscles
what is the somatic motor innervation of the pump muscles?
diaphragm: phrenic nerve (from cranial plexus C3-C5)
intercostal muscles: T1-T12
abdominal muscles: forced expiration: thoracic, lumbar (predominantly)
what is the name of the pacemaker region in the brain and where is it? what does it do?
Pre-Botzinger in medulla of brainstem — generates a respiratory rhythm in isolation with no sensory input
what respiratory groups are there?
- ventral and dorsal respiratory groups if the medulla (pattern generation)
- pontine respiratory groups in pons (respiratory pattern)
where are peripheral chemoreceptors detected?
carotid bodies (bifurcation of common carotid artery in neck), aortic arch
what do the peripheral chemoreceptors detect?
drop in pH, rise in PCO2, drop in PO2 (hypoxia)
where are the central chemoreceptors?
on the surface of the medulla
what do the central chemoreceptors detect?
rise in PCO2, not pH, not hypoxia
what do the central chemoreceptors respond to to increase ventilation?
respond to an increase in H+ in the CSF which increases ventilation (cerebrospinal fluid)
levels of what is the main driver of breathing?
CO2 from the blood
what can and cannot pass the blood brain barrier?
HCO3 and H+ cannot, but CO2 can diffuse into the extracellular space of the brain
CO2 + H2O —> HCO3- + H+ — this H+ is detected by the central chemoreceptor
what happens to ventilation at high levels of CO2?
has an affect on the CNS - acts as an anaesthetic so ventilation plateaus, become sleepier
what is the effect of low oxygen on ventilation?
increases ventilation
sensory input of nose
trigeminal (V)
sensory input of pharynx
- glossopharyngeal (IX)
- vagus (X)
sensory input of larynx
- vagus (X)
sensory input of lungs
vagus (X)
sensory input of chest wall (muscles + tissues)
spinal nerves
where are the pulmonary stretch receptors and what do they respond to?
- mainly in trachea and main bronchi
- respond to lung inflation
where are the irritant receptors and what do they respond to?
- in naso-pharynx, larynx, trachea and bronchi
- respond to mechanical, chemical irritant stimuli, inflammatory mediators
what are c-fibres, where are they and what do they respond to? (juxtacapillary receptors)
- receptors “free” nerve endings
- in larynx, trachea, bronchi, lungs (J-receptors) (conducting airways)
- respond to chemical irritant stimuli, inflammatory mediators, lung oedema (J-receptors)
what does the motor cortex of the brain drive?
drives voluntary muscles and voluntary motor movements
voluntary breathing produces brain activity within what?
the motor homunculus
what is upper airway patency maintained by?
- neuromuscular forces — dilator muscles actively dilate and/or stiffen the pharynx — keep airway open, contraction of muscles
- extraluminal forces — gravitational forces, adipose tissue — reduce/collapse patency
what is apnoea?
the cessation of breathing
how do PaCO2 and O2 saturation levels change at night?
alveolar ventilation decreases:
- PaCO2 increases
- O2 saturation decreases
