Vagus nerve Flashcards
is the vagus nerve a motor, sensory or mixed nerve?
Mixed
What are the 3 types of sensory fibers from the vagus nerve?
Somatosensory neurons
Gustatory neurons
general visceral afferent neurons
Where are the cell bodies of the vagus nerve somatosensory neurons?
superior ganglion of the X nerve
where are the peripheral processes of the vagus nerve distributed to?
1) some skin of the external ear
2) part of the external auditory
3) lower pharynx
4) larynx
5) upper esophagus
What tract do the central processes of the somatosensory vagus nerve join and where does it terminate?
Central processes enter brainstem, join the spinal tract of the trigeminal nerve and terminate in the spinal trigeminal nucleus
Where do the fibers of the vagus nerve carrying somatosensory information travel from the spinal trigeminal nucleus?
fibers of the second order neurons ascend to the VPM nucleus of the thalamus through the trigeminothalamic tract
Where does somatosensory vagus information travel from the VPM nucleus?
neurons of VPM nucleus send fibers through the posterior limb of the internal capsule to the primary somatosensory cortex
Where are the primary sensory neurons of the gustatory neurons of the vagus nerve found?
Primary sensory neurons in the inferior ganglion of the X nerve
Where do the peripheral processes of the gustatory neurons of the vagus nerve innervate?
Taste receptors on the epiglottis
Where do the central processes of the gustatory neurons terminate?
Solitary nucleus (rostral part)
Where do the fibers of the gustatory neurons of the vagus nerve travel from the solitary nucleus?
Fibers ascend the brainstem through the ipsilateral central tegmental tract to terminate in the VPM nucleus of the thalamus
Where do the gustatory neurons of the vagus information travel from the VPM nucleus?
Thalamic neurons project axons to the “taste” area of the cerebral cortex in the parietal love and insula
Where are the primary sensory neurons of the general visceral afferent neurons of the vagus nerve found?
cell bodies in the inferior ganglion of the X nerve
Where do the peripheral processes of the general visceral afferent neurons of the vagus nerve innervate?
1) baroreceptors in the aortic arch
2) chemoreceptors in the aortic arch
3) receptors in organs of the thoracic and abdominal cavities to monitor stretch or distension of hollow organs in the thoracic and abdominal cavities including the transverse colon
Where do the central processes of the general visceral afferent neurons terminate?
descend in the medulla in the solitary tract and terminate in the solitary nucleus
What are the two motor components of the vagus nerve?
Somatomotor (lower motor neurons)
parasympathetics
Where are the primary neurons of the somatomotor neurons of the vagus nerve found?
Cell bodies located in the nucleus ambiguus in the medulla
How do the fibers of the somatomotor neurons of the vagus nerve emerge from the brainstem?
1) part of the vagus nerve
2) as the cranial root of the spinal accessory nerve (provide X nerve innervation to muscles)
Where do the motor fibers of the X nerve supply?
1) All muscles of the palate except tensor veli palatini
2) All pharynx muscles except stylopharyngeus
3) All intrinsic larynx muscles
4) Muscles of upper esophagus
Does the somatomotor fibers of the X nerve contain unilateral or bilateral corticobulbar innervation?
Bilateral
With an upper motor neuron unilateral lesion of the vagus nerve what happens?
no paralysis of muscles innervated by the X nerve
Where are the primary neurons of the preganglionic parasympathetic neurons of the vagus nerve found?
cell bodies comprise the dorsal motor nucleus of the vagus in the medulla (some in the nucleus ambiguus)
How do the fibers of the preganglionic parasympathetic neurons of the vagus nerve distributed and terminate?
Fibers are distributed with the vagus nerve and terminate in terminal or intramural ganglia in or near the organ they supply
where are postganglionic fibers of the vagus nerve distributed to the visceral effector cells?
Smooth muscle, cardiac muscle and gland cells to thoracic and abdominal cavities. In the GI tract through to the transverse colon
What occurs in a unilateral lesion of the vagus nerve?
ipsilateral paralysis of muscles of the pharynx, larynx and palate;
Horseness of voice
dyspnea
dysphagia
What happens with the uvula during phonation with an ipsilateral lesion of the vagus nerve?
uvula deviates to the controlateral side in regards to the lesion
What happens to the vocal folds with an ipsilateral lesion of the vagus nerve?
The ipsilateral vocal fold adducts
What occurs in a bilateral lesion of the vagus nerve?
paralysis of muscles of larynx pharynx and palate
What is the outcome of a bilateral lesion of the vagus nerve?
Often die because vocal folds dive inwards
