Lecture 15 Unit 2 Flashcards
how do respiratory and skeletal muscles contract?
by the action of motor neurons
unlike other skeletal muscles, the respiratory muscle are under both______?
automatic and voluntary control
what does automatic respiratory muscle control depend on?
groups of inspiratory and expiratory neurons in the medulla oblongata
where are phrenic motor neurons located?
C3-C5 spinal segments
where are inspiratory neurons localized into?
a functional group known ad the dorsal respiratory group (DRG)
where are expiratory neurons located?
ventral respiratory group (VRG)
what are pre motor neurons?
they synapse on and excite motor neurons to respiratory muscles
since breathing is rhythmic, what does it depend on?
“pacemaker like” activity in brain stem neurons that alternately turn the inspiratory neurons on and off
when are expiratory neurons activated?
when breathing activity must be increased
what happens in the pneumotaxic center
negative effect (inhibition)
what happens in the apneustic area?
positive effect (stimulation)
where are the DRG and VRG located in the brain
pons and medulla
what are the various specialized receptors that inform the neurons about the body’s needs for ventilation?
- pulmonary stretch receptors
- central chemoreceptors
- peripheral chemoreceptors
where are pulmonary stretch receptors located?
in the msotth msucle that lines some of the large conducting airways, bronchi, and bronchioles
what do pulmonary stretch receptors respond to?
when bronchioles are inflated or stretched
the pulmonary stretch receptors are innervated by axons from what nerve?
vagus (CN X)
what is the influence of stretch receptors?
the DRG switches from inspiration to expiration more quickly - lung inflation stops and lung deflation begins
where are central chemoreceptors located
beneath the ventral surface of the medulla
what do central chemoreceptors respond to?
low pH and high P(CO2) in CSF
what is low pH in the CSF the result of?
CO2 that diffuses into the CSF from the blood and forms hydrogen ions
where are peripheral chemoreceptors located?
in the aortic arch and in the carotid sinus
what do peripheral chemoreceptors mainly respond to?
low oxygen levels in arterial blood
what do peripheral chemoreceptors weakly respond to?
low pH and high CO2 levels
peripheral chemoreceptors are innervated by axons that travel from where?
glossopharyngeal nerve and vagus nerve (cranial nerves IX and X)
