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Brainstem Flashcards

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1
Q

How is the brainstem named by planes/directions?

A
  • Inferior to the midbrain-diencephalic jxn:
    • Rostral = up
    • Caudal = down
    • Ventral = Nose
    • Dorsal = Back
  • Superior to the midbrain-diencephalic jxn:
    • Dorsal = up
    • Ventral = down
    • Rostral = nose
    • Caudal = back
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2
Q

Where are the ventricles of the brain?

A
  • Forebrain: 2 C-shaped lateral ventricles with own choroid plexus
    • CSF from these drains into intraventricular Foramen of Monroe into Third Ventricle
  • ​Third Ventricle: surrounded by diencephalon (midbrain diencephalic jxn) –> connects with Fourth Ventricle via cerebral aquaduct
    • ​Choroid plexus on roof of third ventricle
    • Cerebral Aquaduct = Aquaduct of Sylvius in midbrain
  • Fourth Ventricle: on dorsal side, shared between pons and medulla
    • start of central canal that continues into spinal cord
    • own choroid plexus to produce CSF
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3
Q

What are the 3 exit points for CSF circulation in the brainstem?

A
  • Medial (x1): Foramen of Magendie
  • Lateral (x2): Foramina of _L_uschka
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4
Q

Where does the CSF drain?

A

CSF drains through Magendi and Luschka into Cisern Magna

Note: it is possible to obtain CSF sample from subarachnoid space of Magna.

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5
Q

What are the cisterns?

A
  1. Interpeduncular
  2. Quadrigeminal
  3. Magna (largest cistern; collects CSF from fourth ventricle)
  4. Prepontine

All connected in subarachnoid space via blood vessels

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6
Q

Visualize the circulation of CSF in subarachnoid space

A
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7
Q

Pyramidal (CST) Pathway

A

Conduit fxn of brainstem:

  1. Cortext –> Internal capsule –> IC exits out as part of cerebral peduncles in midbrain –> travel through Pons –> first “bump” in medulla (pyramids) –> cross at end of medulla (most cross to contralateral side = LCST; small portion stays uncrossed as ACST)
  2. Crosses at caudal medulla (no fourth ventricle on dorsal side)
    1. This is the end of the brainstem and begining of spinal cord (cervicomedullary jxn)
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8
Q

Describe the corticonuclear (bulbar) pathways:

  • what do they do?
  • where are the 1st and 2nd order neurons?
  • bilateral or ispilateral?
A
  • what do they do?
    • descending control & modulation of sensory and motor nuclei of cranial nerves
  • where are the 1st and 2nd order neurons?
    • ​1st order: widespread ares of cerebral cortex
    • 2nd order: in pontine& medullary reticular formation & nuclei of cranial nerves
  • bilateral or ispilateral?
    • ​mostly bilateral
      • ​mostly crossed for nucleus of CN XII and for n. ambiguous innervation of soft palate and uvula (CN X)
    • only ipsilateral for nucleus of CN XI
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9
Q

What are the nuclei-gracillis and cuneatus fibers?

A

2nd order DCML fibers

  • discriminative touch, pressure, proprioception
    • 1st order: large myleinated fibers of DRG
    • 2nd order: nuclei-gracillis and cuneatus fibers decussate as internal arcuate fibers
    • 3rd order: VPL nucleus of thalamus
  • Crossed at the lower medulla
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10
Q

Compare the DCML and ST pathways in the medulla

A
  • DCML:
    • 2nd order neuron in medulla
    • travels through medial medulla
  • ST:
    • 2nd order neuron in spinal cord
    • travels through lateral medulla
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11
Q

One motor and one sensory pathway make synapses in the medulla - what are they?

A

corticobulbar and DCML

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12
Q

One motor and one sensory pathway travels through the medulla - what are they?

A

corticospinal and spinothalamic (anteirolateral system) pathways

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13
Q

How can you visually tell you are in the medulla?

A
  • pyramidal decussation
  • Lower medulla: still looks like complete circle bc of proximity to spinal cord
  • Upper medulla: look for snake-like inferior olive
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14
Q

What is the differenec btwn nerve and tract?

A

Nerve: in touch of periophery

Tract: touch with CNS

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15
Q

Which CNs are sensory? Mixed? Motor?

A

3 Sensory: I, II, VIII

4 Mixed (both): V, VII, IX, X

5 Motor: III, IV, VI, XI, XII

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16
Q

What are the classificaitons of the motor “efferent” nuclei?

A
  • Somatic (skeletal muscles from somites - extraocular and tongue muscles)
  • Visceral (activate viscera or organs)
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17
Q

What are the subdivisions of the motor “efferent” visceral nuclei?

A
  • General: preganglionic parasympathetic fibers for cranial, thoracic, and abdominal smooth muscles (viscera)
  • Special: activates striated muscles (not from embryonic somites but from branchial arches)
    • muscles of facial expression, jaw muscles, laryngeal and pharyngeal muscles, SCM, trapezius
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18
Q

Contrast the somatic and visceral sensory (affarent) nuclei?

A
  • Somatic: carries info about changes in environment from framework of the body (receptors)
  • Visceral: refers to impulses arising in / around the viscera or organs
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19
Q

Contrast general vs special somatic sensory nuclei

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A
  • General: impulses that begin at/ear body surface - pain, temp, touch, pressure
  • Special: highly specialized = vision and hearing
20
Q

Contrast general vs special visceral sensory nuclei

Study These Flashcards
A
  • General: receptors in/on mucous membrane or organ wall impulses abt physcial distension of chemical composition of organ wall
  • Special: smell and taste
21
Q

CNs

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A
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22
Q

Cranial Nerve Classification of midbrain vs. pons, vs medulla

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A

Rule = 2:2:4:4 (Out:Midbrain:Pons:Medulla

  • 2 Out: I and II
  • 2 Midbrain: III and IV
  • 4 Pons: V-VIII
  • 4 Medulla: IX-XII
23
Q

Where are the motor nerve nuclei in the brainstem vs. sensory

Study These Flashcards
A
  • Motor tend to be medial
    • General somatic most medial: III, IV, VI, XII
    • Special visceral: V, VII, IX, X, XI
    • General visceral most lateral of the medial: III, VII, IX, X
  • Sensory tend to be lateral
    • Most lateral: VIII
24
Q

Cranial Nerves in the Medulla

Study These Flashcards
A
  • IX: Glossopharyngeal (Both)
  • X: Vagus (Both)
  • XI: Accessory (Motor)
  • XII: Hypoglossal (Motor)

Note: XII exits between the Olive and Pyramid bumps from vental view but from dorsal view the hypoglossal nucleus is seen above the obex in the hypoglossal triangle

25
What does CN XII do
General somatic efferent (GSE) for ipsilateral muscles of the tongue * controls movement of the tongue and maintains muscle tone * innervates all intrinsic muscles and all but one of the extrinsic tongue muscles (palatoglossus muscle supplied by CN X. * LMNs of CN XII nucleus extend the full length of the medulla as a cell column *Recall: UMNs for XII (voluntary movements and articlation) is supplied by corticobulbar pathway, which is mainly crossed (contralateral) for XII. While reticular neurons for automatic/reflex movements - control of stereotyped movements while eating and swallowing)*
26
What happens if you lesion left corticobulbar tract?
Lost innervation to R hypoglossal nucleus: so right side will be weaker and you will be pushing hte tongue to the lesioned side ## Footnote **_UMN lesion:_ Tongue moves _opposite_ to the lesion** **_​LMN lesion:_ Tongue moves _to same side of_ the lesion (accompanied by sever muscle atrophy)**
27
What are the most common causes and consequenes of CN CXII lesions?
* Common Causes: * motor neuron disease * demyelination * bleeding * tumors of medulla and base of the skull * Results: * considerable speaking disability * severe swallowing difficulty
28
CN XI
* Motor - SVE (special visceral efferent) * moves neck and shoulder * LMN in medulla and cervical cord (C1-C5) - some from medulla and some from ventral horn * pyramidal decussation of gracile and cuneate nucleus * Lesion: * cannot rotate head to healthy side against pressure * ipsilateal shoulder drop * weakened voice/hoarseness
29
What are the two efferent (motor) components of the vagus nerve (CN X)?
1. GVE: preganglionic parasympathetic * ganglia for heart, lungs, GI to the splenic flexure 2. SVE: swallowing (pharyngeal muscles) and vocalization (laryngeal muscles)
30
What are the three sensory components of the Vagus?
1. GDA - *conscious sensory* * touch, pain, pressure for small parts of the face 2. SVA - *conscious sensory* * taste from epiglottis and pharynx 3. GVA - *subconscious sensory* * chemo and baroreceptors of the aortic arch
31
Preganglionic sympathetic and parasympathetic fibers use which neurtransmitter?
Ach
32
What does the GVE of CNX do?
* General visceral efferent (start of pregang PS for ganglia of heart, lungs, GI to splenic flexure * Uses the dorsal motor nucleus in medulla
33
Where is the nucleus ambiguus and what does it do?
* Efferent motor - SVE = swallowing and vocalization * located on dorsal side in middle of/near inferior olivary nucleus
34
What parts of the face are supplied by CN X sensory? What types of senses?
Touch, pain, temp to: 1. Pharynx + larynx (parallels motor innervation) 2. meninges of the posterior fossa 3. small region of the outer ear (Afferents join nucleus of CN V)
35
What nucleus covers SVA taste from epiglottis and posterior pharynx ("conscious sensory") AND GVA from chemo/baroreceptors of aortic arch, cardioresp, and GI ("subconscious sensory")?
**Nucleus soltarius** "Donut shaped"on cross-section of cell-bodies surroudning fibers *NB: it's close to motor nucelus fibers of CN X so allows quick motor response for parasympathetics*
36
What do the rostral and caudal parts of the **solitary nucleus** sense?
*think: smiley face/U shape:* 1. Rostral: taste signals (tip of smile - corners of mouth) 2. Caudal: baroreceptor and chemoreseptor (middle of smile) 3. Caudal: sensory viceral signals from thoracic and abdominal viscera
37
3 nuclei of vagus
1. Dorsal motor nucleus * *pregang PS for heart/lungs/GI* 2. N. Ambiguous * *swallowing and vocalization* 3. N. Solitarius * *sensory: taste and chemo/baroreceptors*
38
What are the effects of a CN X lesion: * *complete bilateral lesion?* * *unilateral lesion?*
* *complete bilateral lesion:* FATAL * *unilateral lesion:* * RIGHT lesion --\> * RIGHT palatal arch sagging * RIGHT vocal muscle paralysis * uvula deviation to LEFT
39
What are the components of CN IX (glossalpharyngeal)? (motor and sensory)
* 2 efferent motor components * GVE: general visceral efferent (pregang PS) for only the **parotid gland** * SVE: **stylopharyngeal muscle** * 3 affferent sensory components * GSE: *conscious* * *​*touch/pain/pressure to pharynx, posterior 1/3 of tongue, middle ear, small region of external ear * SVA: *conscious* * ​taste from posterior 1/3 of tongue * GVA: *subconscious* * *​*chemoreceptors and baroreceptors of carotid body
40
Where is the nucleus for the parotid gland and it's innervation?
* CN IX (glossopharyngeal) GVE * **inferior salivatory nucleus in the PONS** (not in medulla)
41
What is the nucleus of posterior 1/3 of tongue's taste (CN IX - SVA) and the chemoreceptors and baroreceptors of the carotid body (CN IX- GVA)?
**Nucleus soltarius** (join CN X)
42
What are common causes /effects of lesions with CN IX and X?
* Lesions of N. ambiguus * *poliomyelitis* * *ischaemic lesions* * *intramedullary tumors* * *intramedullary tumors* * *motor neuron disease* * *neuronma* * *myastenia gravis* * *Glossopharyngeal neuralgia* - episodes of severe throat and ear pain
43
What does sulcus limitans divide?
Sensory and motor nuclei in medulla (derived from embryology)
44
Blood supply of medulla
* AICA: * **PICA:** * lateral structures * anteriolateral structures (pain and temp) * N. soltarius * Vestibular nuclei * N. ambiguous * PSA (posterior spinal artery) * **ASA (anterior spinal artery)** * covers midline structures: pyramids, medial leminiscus, hypoglossal nucleus * **Vertebral Artery:** * inferior olivary nucleus
45
What is **medial medullary syndrome** and what is the associated vasculature?
* **Anterior spinal artery (ASA)** * Affects **medial structures** * A lesion causes: *ipsilateral for face and contralateral for body* * Ipsilateral tongue weakness (hypoglossal nucelus) * Contralateral arm or leg weakness (motor) * Contralateral decreased position and vibration sense (DCML coming from opposite side) * Pain and temp spared (bc ST is too lateral to be affected)
46
What is **lateral medullary syndrome** and what is the associated vasculature?
* **Posterior inferior cerebellar artery (PICA)** * **Lateral structures affected** * A lesion causes: *ipsilateral face; contralateral body* * ipsilateral decreased taste (N. soltarius affected) * horasness dysphagia (N. ambiguous affected) * contralateral body decreased pain and temperature
47

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