CH14: Cranial nerves 3 Flashcards
sensory fibers of CN IX (glossopharyngeal)
- soft palate
- pharynx
- taste receptors in posterior tongue
glossopharyngeal nerve autonomic innervation?
Autonomic afferents from the carotid sinus signal blood pressure spikes in the carotid artery.
motor fibers of CN IX innervate:
- pharyngeal muscle
- parotid salivary gland
reflexes mediated by glossopharyngeal nerve
- gag
- swallowing
What is the gag reflex?
Pharyngeal muscles contracts when pharynx is touched
What is the swallowing reflex?
Soft palate moves and pharyngeal muscles contracts when food touches entrance of pharynx
Far-reaching connections allow the vagus nerve to:
- decrease HR
- constrict bronchi
- affect speech production
- increase digestive activity
How can motor function of the vagus nerve be tested?
eliciting the gag reflex
gag reflex
- afferent
- efferent
- glossopharyngeal
- vagus
swallowing reflex
- afferent
- efferent
- glossopharyngeal
- vagus
The vagus nerve provides afferent and efferent innervation to
- larynx
- pharynx
- viscera
The vagus nerve produces (sympathetic/parasympathetic) activity
parasympathetic
Where are parasympathetic fibers of the vagus nerve distributed?
- larynx
- pharynx
- trachea
- lungs
- heart
- GI tract (minus large intestine)
- pancreas
- gallbladder
- liver
vagus nerve: location of afferent cell bodies
inferior nucleus of the vagus (outside the brainstem)
vagus nerve: location of efferent cell bodies
- nucleus ambiguous
- dorsal motor nucleus of vagus
(both in the medulla)
CN XI provides motor to
- trapezius
- SCM
path of CN XI
- originates in spinal accessory nucleus in upper cervical cord
- travels through foramen magnum
- leaves skull
CN XI leaves the skull through the
jugular foramen
cell bodies of CN XI are located here
ventral horn (C1-4)
CN XII provides motor to
intrinsic and extrinsic muscles of the ipsilateral tongue
CN XII cell body locations
hypoglossal nucleus of medulla
What is activity of CN XII controlled by?
voluntary and reflexive neural circuits
3 stages of swallowing
- oral
- pharyngeal/laryngeal
- esophageal
CNs involved in oral stage of swallowing
5 7 9 10 12
CNs involved in pharyngeal/laryngeal stage of swallowing
9
10
CNs involved in esophageal stage of swallowing
10
CNs involved in speaking
5
7
10
12
Sounds are generated by the
larynx
At the CN level, sounds generated by the larynx (CN _) are articulated by these
X
- soft palate (X)
- lips (VII)
- jaws (V)
- tongue (XII)
Which CNs contain LMN fibers?
3-7
9-12
How is activity of motor fibers in CNs controlled?
- through descending inputs from voluntary and limbic structures of the brainstem and cerebrum
- also via local reflex mechanisms
CN efferents receive descending regulation from
- corticofugal tracts
- limbic system
Descending limbic pathways and corticobulbar tract relationship (together/separate)
separate
descending control of eye movements
- voluntary
- automatic
descending control of speaking
mostly voluntary, but can occur automatically in highly emotional contexts
What may be preserved in instances in which brain damage interferes with voluntary speech?
ability of the limbic system to produce emotionally charged (i.e. profanity)
How do extreme emotions interfere with the ability to eat and speak?
activating limbic pathways that influence motor activity
