Mod 9 Brainstem Flashcards
What are the functions of the brainstem?
- conduit
- origin of cranial nerves
- integration of CN reflexes, respiratory and CV function, and consciousness
What is the somatosensory system of the head and neck?
trigeminal system
What does the trigeminal system do?
mediates somatosensory info from CN V, VII, IX, and X
What are the three divisions of the trigeminal nerve?
- ophthalmic (V1)
- maxillary (V2)
- mandibular (V3)
What region of he face gets somatosensory innervation from each division of CN V?
V1 - forehead
V2- cheeks
V3 - jaw
What is the direction of the trigeminal system?
sensory info comes into trigeminal ganglion, then synapses on the nuclei in the brainstem, then synapse in the thalamus at the ventral posteriomedial nucleus (2nd order neurons), then 3rd order neurons head to the somatosensory cortex
What is trigeminal neuralgia?
disease of PNS affecting the trigeminal ganglion or nerve (before synapse on the brainstem)
What is another name for trigeminal neuralgia?
tic douloureux
What are the symptoms of trigeminal neuralgia?
brief attacks of excruciating pain in one or more divisions of CN V
What is one surgical intervention that can be used to treat trigeminal neuralgia?
seondary neurons of the trigeminal system sectioned off (Spinal trigeminal tract) that relieves pain attacks but produces the loss of temp and pain on the ispilateral face
How are brainstem reflexes similar to spinal cord reflexes?
have receptors, afferent/efferent fibers, a reflex center, and effector
What are the four brainstem reflexes?
- jaw jerk
- corneal blink
- stapedius
- swallowing
What CN control the jaw jerk reflex?
CN V for both sensory and motor
What CNs control the corneal blink reflex?
CN V: sensory
CN VII: motor
What CNs control the stapedius reflex?
CN VIII: sensory
CN VII: motor
What CNs control the swallowing reflex?
CN IX and X: sensory and motor
What type of reflex is the jaw jerk reflex?
monosynaptic
What happens in the jaw jerk reflex?
muscle spindles respond to quick stretch of masseter muscles, creating a bilateral response of contracting masseter muscles
What happens in the corneal reflex?
unilateral stimulus of stroke to cornea producing a bilateral response (blinking of both eyes)
What happens during the stapedius reflex?
load sound enters one ear causing the stapedius muscle to contract bilaterally
How does the stapedius reflex work?
stapedius stiffens the ossicular chain, dampening the sound transmission making the sound quieter, protecting our ears
What are the afferent and efferent limbs of the stapedius reflex?
afferent: cochlear div fibers of CN VIII
efferent: LMN of CN VII
What is the path of the stapedius reflex?
CN VIII prim aff -> ventral cochlear nucleus -> bilateral projection to superior olivary nucleus -> interneurons to CN VII -> stapedius muscle
What is the swallowing reflex?
when a bolus of food stimulates the walls of the oropharynx, the reflex is triggered
What are the stages of the swallowing reflex?
- voluntary
- reflexive
- reflexive
What are the afferent and efferent limbs of the swallowing reflex?
afferent: sensory CN IX, X
efferent: motor CN IX, X
What is the corticotubular tract?
descending tracts from the cerebral Cortez to the brainstem, controlling innervation of CN motor nuclei
What is another name for UMN fibers in the corticotubular tract?
supranucleur because its above the nuclei in the brainstem
Where does the CBT descend?
in the internal capsule adjacent to CST fibers
How can you tell if an UMN or LMN is impacted in CN VII innervation?
UMN: droop in the lips but not the eyebrows
LMN: droop in both eyebrow and lip
Why are you able to tell if an UMN or LMN is affected in CN VII facial innervation?
the eyebrows are dual innervated by two UMN, so if is not functioning it means it will only cause a droop of the lips
What is progressive Bulbar Palsy?
motor system disease dominated by weakness of the orofacial muscles
What are the symptoms of Progressive Bulbar Palsy?
dysarthria. impaired chewing and swallowing, atrophy of tongue
*maybe pathological crying and laughing
What causes Pseudobulbar Palsy?
bilateral lesions of internal capsule affecting CBT
What are the symptoms of Pseudobulbar PalsY?
pathological laughing and crying along with bilateral bulbar signs
What is another name for Pseudobulbar Palsy?
spastic bulbar paralysis
What is dysarthria?
motor deficits in the production of articulated speech
What causes dysarthia?
stroke, trauma, disease
damage to UMN or LMN subserving muscles of articulation
What is important about the structure of the reticular formation of the brainstem?
dendritic trees overlap extensively creating a net like form
How do the neurons of the reticular formation interact with ascending and descending tracts?
these tracts give collaterals that intermingle with neurons of reticular formation
What are the functions of the reticular formation?
- control level of consciousness
- modulate pain
- regulate motor activity
- coordinate vision
- control autonomic activity
What are the two routes of the control of consciousness in the reticular formation?
- noradrenergic and serotinergic neurons (serotonin)
- generalized thalamocortical system (ACh)
How does descending modulation of pain work?
neurons of brainstem reticular formation release transmitters onto dorsal nuclei of spinal cord
locus coeruleus: Noepinephrine
raphe nuclei: serotonin
to help decrease sensation of pain
How does the regulation of motor activity of the reticular formation of the brainstem work?
reticulospinal tracts can facilitate or inhibit voluntary movement and reflex activity
How does coordination of vision work in the reticular formation of the spinal cord?
paramedian pontine reticular formation: horizontal gaze center
rostral interstitial nucleus of the medial longitudinal fasciculus: vertical gaze center
How does control of autonomic activity for with the reticular formation of the brainstem?
centers for HR, BP, and respiration
damage in RF can lead to coma and/or death due to this control
Where do noradrenergic neurons originate?
locus ceruleus and contain norepinenphrine
What role do noradrenergic neurons play?
maintaining alertness and vigilance
How do noradrenergic neurons work?
excites spinal cord ventral horn and inhibit dorsal horn
electrically silent during sleep, somewhat active in wake, most active in startle
Where do dopaminergic neurons originate?
pars compact of substantia nigra
contain dopamine
What do dopaminergic neurons do?
imitation of movement, likely cognition and emotion
Where are serotinergic neurons located?
raphe nuclei
What do serotnergic neurons do?
excite spinal cord ventral horn, inhibits dorsal horn
arousal and modulation of pain
Where are cholinergic neurons located?
RF, basal forebrain, caudate putamen
What are the receptors of cholinergic neurons?
PNS: nicotinic
CNS: muscarinic
What role do cholinergic neurons play?
sleep and wakefullness
How is the brainstem organized?
- CN attachments
- long ascending and descending tracts throughout brainstem
- presence and shape of ventricular system
- three pairs of cerebellar peduncles attach to cerebellum and brainstem
Where are sensory and motor nuclei located on the brainstem?
sensory: lateral
motor: medial
What vessels supply blood to the brainstem?
vertebrobasilar system
- 2 vertebral arteries
- single basilar artery
- posterior cerebral arteries
What does occlusion of the PICA result in?
lateral medullary syndrome (Wallenburg’s syndrome)
What does occlusion of the paramedian branches of the anterior spinal arteries result in?
Dial medullary syndrome (alternating hypoglossal hemiplegia, or inferior alternating hemiplegia)
What anatomical structures are affected in lateral medullary syndrome?
- spinal trigeminal tract and nucleus
- STT
- descending sympathetic fibers
- nucleus ambiguus fibers of CN IX, X, XI
- vestibular nuclei
- inferior cerebellar peduncle
What are the symptoms of lateral medullary syndrome (Wallenberg’s Syndrome)?
- impaired pain and temperature sensation over ipsilateral face and contralateral body
- ipsilateral Horner’s syndrome
- disequilibrium
- impaired eye movement control
- dysphonia
- dysphagia
- dysarthria
What structures are affected in medial medullary syndrome?
- hypoglossal nucleus and/or exciting CN XII fibers
- corticospinal tract
- medial lemniscus
What is another name for medial medullary syndrome?
alternating hypoglossal hemiplegia
What are the symptoms of medial medullary syndrome?
- loss of discriminative touch and kinesthesia
- spastic hemiparesis of contralateral body
- LMN weakness and atrophy of ipsilateral tongue
What vessels nourish the pons?
branches of basilar artery
What are syndromes associated with infarcts on the pons?
- medial (paramedian) inferior pontine syndrome
- lateral superior pontine syndrome
- complete basilar syndrome
- locked in syndrome
What is Locked-In Syndrome?
- infarct confined in ventral pons spares ascending reticular activating system
- damaged bilateral corticobulbar and corticospinal tracts
- person fully conscious but locked in with near total paralysis
- only some eye movements remain
What causes Weber’s syndrome and what is another name for it?
infarction of branches of PCA
superior alternating hemiplegia
What structures are damaged in Weber’s syndrome?
descending tracts in cerebral peduncle, nucleus for CN III
What are the symptoms of Weber’s syndrome?
spastic hemiparesis of contralateral body and lower half of face
ipsilateral oculomotor palsy
