Week 2 Flashcards
(48 cards)
1
Q
where does the medulla oblongata end?
A
- lower part of the medulla oblongata is passing through foramen magnum
(ends at the upper border of 1st cervical vertebra) - that’s why in case of increased intracranial pressure in the posterior cranial cavity the
lower part of medulla oblongata and the cerebellum herniate
2
Q
ventricles of the brain and where they’re at
A
- lateral ventricles -> cavity of the cerebrum lt and rt
- 3rd ventricle -> between the rt and lt thalamus
- interverteral foramin for lateral ventricles and 3rd ventricles to communicate
- cerebral aqueduct
- cerebral aqueduct -> cavity of the midbrain
- 4th ventricle -> cavity of pons and upper part of medulla
3
Q
4th Ventricle communicates with subarachnoid space through?
A
foramen of Luska (related to medulla oblongata)
and foramen of Magendie
4
Q
What’s Cisterna magna?
A
spacious part of subarachnoid space, aka cerebellomedullary cistern is related to the dorsal side of the medulla oblongata. (btw medulla and cerebellum)
5
Q
where is the Interpeduncular fossa/cistern of subarachnoid space?
A
lies between the two crus cerebri of the midbrain.
6
Q
fourth ventricle continues down as?
A
the central canal of the medulla oblongata
7
Q
can divide the medulla into two parts
A
lower closed part where the central canal of medulla oblongata is present and upper open part of the medulla oblongata where the fourth ventricle is present
8
Q
central canal extends through out the spinal cord and expands in the lumbar enlargement as?
A
terminal ventricle
9
Q
csf which is produced by?
A
choroid plexus (tough capillaries covered by ependyma)
so the csf is produced by the choroid plexus of the lateral ventricle the 3rd ventricle and the 4th ventricle
10
Q
Where csf circle
A
csf comes from the lateral ventricles
> interventricular foramen
> the third ventricle
> cerebral aqueduct (narrowest part of ventricular system)
> the fourth ventricle
> general subarachnoid space (median aperture and 2 lateral aperture)
> central canal of medulla
> central canal of spinal cord
11
Q
CSF gets absorbed into?
A
Dural venous sinus via the arachnoid villi (bcz of pressure difference)
12
Q
ventricle communicate with the subarachnoid space at 3 points (where the CSF goes)
A
CSF flows from ventricles to subarachnoid space via
- the whole circle
- median aperture
- lateral aperture
13
Q
cranial nerves in midbrain and their locations
A
- from 2 to 12
- trochlear (4) is the only cranial nerve arising from the dorsal aspect of the mid brain and it is crossed
- midbrain: 3, 4
- pons: 5
- btw pons and medulla: 6, 7, 8
- medulla: 9, 10, 11 are posterolateral, 12 is anterolateral
14
Q
Lower part of the medulla is closed by:
A
decussation of (crossing) the pyramids ( some fibers of the corticospinal tract cross here)
15
Q
Between pyramid and olive is
A
anterolateral sulcus (Rootlets of hypoglossal nerve are attached here)
16
Q
Posterior to olive is
A
the posterolateral sulcus
17
Q
olive is produced by grey matter inside that part of the brain which is called
A
inferior olivary nucleus
18
Q
in the anterior midline of the medulla there is
A
anterior medial fissure
19
Q
accessory nerve (11th) has two parts:
A
- fibers attached to the posterolateral sulcus forms the CRANIAL ROOT of accessory nerve (distributed through the vagus nerve)
- ) fibers coming from the upper five segments of the spinal cord forms the SPINAL ROOT root of the cranial nerve (supplies the two muscles in the neck region)
20
Q
Medulla, at the lvl of motor decussation
A
- aka decussation of pyramid (lower part of medulla)
- called motor decussation lvl bcz fibers of the corticospinal tract cross here
- 2/3rd of corticospinal fibers present within the pyramid run backwards and laterally and cross the midline -> become lateral corticospinal tract (crossed in the lower part of medulla)
- Uncrossed corticospinal fibers -> anterior corticospinal tract.
- Spinocerbellar tracts, spinothalamic tracts ascend in the lateral most part of the medulla oblongata.
- Detached part of the ventral grey column gives rise to rootlets of accessory nerve (this occur as a result of the crossing of the fibers)
- Dorsal part ascend to the medulla. (Nucleus Gracilis and Cuneates begin to appear at this lvl)
- in lateral part, the SPINAL nucleus of trigeminal n. and its tract appear
21
Q
IMPORTANT. when tract is affected in brain stem what will be affected contralaterally and what’s ipsilaterally
A
when tract is affected in brain eg. spinothalamic it’s gonna be affected CONTRAlaterally
but if it’s a cranial n. it’s IPSIlateral when brainstem is affected
22
Q
Medulla, at the lvl of sensory decussation
A
- aka decussation of medial lemnisci
- corticospinal fibers produce surface elevation on the ventral (ant.) aspect as pyramids
- Spinocerbellar tracts, spinothalamic tracts ascend to the lateral most part of the medulla
- Accessory nerve nucleus is in more deeper part of the grey mater.
- Inferior olivary nucleus of the Olivary nuclear complex appear at this lvl
- In central grey mater ( i.e around the central canal) MOTOR nucleus of hypoglossal nerve (12) appears.
- medial longitudinal fasciculus (MLF), a small bundle of fibers which inter connect the brain stem cranial nerve nuclei 3, 4, 6, 8 (for coordination of these nerves)
- dorsal part fibers of faciculus gracilis and fasciculus cuneatus synapse w/ their nuclei (Second order sensory fibers of nuclei first run laterally, then turn medially, ross to opposite side and then ascend up as medial lemniscus on their way to 3rd order sensory neurons in the thalamus.)
- in lateral part, the SPINAL nucleus of trigeminal nerve can be seen at this level also (and the accessory cranial nerve nucleus (spinal root))?
23
Q
Origin of the medial laminiscus is:
A
CONTRALATERAL medulla (cuneatus and gracilis nucleus)
24
Q
Three nuclei for vagus:
A
- soliterius -> taste (sensory)
- ambigues -> (motor)
- Dorsal vagal nucleus -> (parasympathetic)
25
Spinal laminiscus
anterolateral column (spinotectal pathway + anterior and lateral spinothalamic)
26
At the level of MIDDLE of the olivary nuclei
- corticospinal fibers produce surface elevation on the ventral aspect as pyramids as in the earlier section
- Arcuate nuclei (Displaced pontine nuclei) -> some of the pontine nuclei migrated to the ventral part of the pyramid making this arcuate nuclei
- Posterior Spinocerbellar tracts is incorporated in the inferior cerebellar peduncle.
- Anterior spinocerbellar tract ascends to superior cerebellar peduncle
- Spinothalamic tracts ascend in the deeper plane and associates with spinotectal tract to form spinal lemniscus
- Inferior olivary nucleus, a bag of grey matter, located lateral to the pyramids and gives rise to ovivocerebllear fibers, main fibers of the inferior cerebellar peduncle
- in the grey mater deep to the floor of the 4th ventricle are:
1. motor nucleus of hypoglossal nerve (12)
2. dorsal nucleus of vagus nerve
3. nucleus of tractus solitarius (taste)
4. MEDIAL vestibular nucleus (for posture and head position)
- INFERIOR vestibular nucleus appears
-
27
At the level of SUPERIOR part of olivary nuclei (just inferior to pons)
- similar to midolivary level
- LATERAL vestibular nuclei appear
- Inferior cerebellar peduncles are associated with dorsal and ventral cochlear nuclei.
28
Salivatory nerves:
1. superior -> facial (7)
| 2. inferior -> glossopharyngeal (9)
29
SO4
| LR6
1. SO4:
superior oblique -> trochlear nerve
2. LR6:
lateral rectus -> abducent nerve
1 and 2 are for eye, they're the exception
الباجي كلهم
oculomotor
30
medial longitudinal fasciculus (MLF) function 3, 4, 6, 8 (for coordination of these nerves)
for eye muscle coordination
| between nerves 3, 4, 6, 8
31
Abducent nerve
abduction, motor
| نطالع طرف عينا
32
parasympathetic nerves
3, 7, 9, 10
33
```
exits of cranial nerves:
Olfactory nerves
Optic nerve
Oculomotor nerve
Trochlear nerve
Abducent nerve
trigeminal nerve (for each division)
Facial nerve
Vestibulocochlear nerve
Glossopharyngeal, Vagus and accessory nerves
Hypoglossal nerve
```
- Olfactory nerves: Cribriform plate of ethmoid bone
- Optic nerve: Optic canal
- Oculomotor, Trochlear, Abducent nerves:
Superior orbital fissure
- trigeminal nerve:
1. .Ophthalmic division -> Superior orbital fissure
2. Maxillary division -> Foramen rotundum
3. Mandibular division -> Foramen ovale
- Facial nerve: Internal acoustic meatus
- Vestibulocochlear nerve: Internal acoustic meatus
- Glossopharyngeal, Vagus and accessory nerves: Jugular foramen
- Hypoglossal nerve: Hypoglossal canal
***vestibulocochlear nerve will go through internal acoustic meatus BUT will NOT go out of the skull bcz it ends in the internal ear, whereas the facial nerve leave the cranial cavity through the internal acoustic meatus which ends into the stylomastoid foramen
34
Glossopharyngeal n. innervations
- Sensory: taste from posterior 1/3 of tongue, general sensations from pharynx, tonsillar sinus, pharyngotympanic tube, middle ear cavity
- Motor: Stylopharyngeus muslce, Secretomotor fibers to parotid gland (through otic ganglion)
35
Accessory n. innervations
- Motor: Sternocleidomastoid and trapezius muscles
36
Hypoglossal n. innervations
- Motor: Intrinsic and extrinsic muscles of the tongue, EXCEPT palatoglossus muscle
37
What's different about Spinal nucleus of trigeminal nerve?
This nucleus extends through out the brain stem
38
each cranial n. and it's nucleus
- Inferior salivatory Nucleus
of glossopharyngeal nerve
- Nucleus ambguus (9, 10)
- Dorsal Nucleus of vagus nerve (9)
- Spinal nucleus of trigeminal nerve
- Rostral gustatory nucleus AND Caudal (visceral or cardiorespiratory nucleus) are TWO Nucleus of Solitory tract (7, 9, 10)
39
vestibular part of vestibulocochlear n.
- conducts the nerve impulses from utricle and saccule of internal ear for info of head POSITION
- impulses from the semicircular canals for info of MOVEMENT of head
- for equilibrium, balance, sense of movement of head
- Sensory neurons are located in the vestibular ganglion ( in the internal acoustic meatus).
40
cochlear part of vestibulocochlear n.
- for hearing
| - spiral organ for corti in cochlea of internal ear
41
Luxol blue stain used for:
highlight the myelin cause it doesnt show on h+e
42
‘Jumping’ of the action potential from one node to the next is called:
Saltatory Conduction
43
Causes of these demyelinating diseases:
multiple sclerosis
progressive multifocal leukoencephalopathy
leukodystrophies
- multiple sclerosis -> Immune-mediated
- progressive multifocal leukoencephalopathy -> Infections
- leukodystrophies -> Metabolic (inherited)
44
Multiple sclerosis (MS):
- autoimmune demyelinating disorder characterized by distinct episodes of neurologic deficits
- chronic inflammatory disease
- destruction of oligodendrocytes
- The drug IFN-beta is thought to reduce antigen presentation and T-cell proliferation
- HLA-DRB1*1501 allele
- (IMPORTANT) T cells (Th1, Th17) cross BBB and attack myelin basic protein
- Autoreactive B cells produce anti-myelin antibodies
- Macrophages attack myelin, they remove necrotic debris
```
- Pathological hallmarks:
• Inflammation
• Demyelination
• Remyelination (though not perfect!)
• Neurodegeneration
• Glial scar formation (gliosis) -> done by astrocytes
```
- Long-standing plaques are firm (sclerosis) because of gliosis
- Hence the name “multiple sclerosis” تصلب متعدد
- Foamy histiocytes:
Macrophages (histiocytes) engulf myelin debris and released lipid material. This indicates active myelin breakdown.
- best test is MRI
- presentation: either elapsing and remitting or progressive
- Relapsing-remitting stage may be followed by a phase of uninterrupted disease progression, termed secondary progressive MS
- depending on the type you either get:
1. ACUTE active plaques are most frequent in -> RELAPSING-remitting MS
2. CHRONIC plaques -> in PROGRESSIVE MS
- Involvement of optic nerve -> unilateral visual impairment
45
Progressive Multifocal
| Leuko/encephalo/pathy:
- encephalitis caused by JC polyoma virus infection of oligodendrocytes
- affect immunosuppressed
individuals
- How it happens?
1. Virus is acquired at a young age and remains latent/dormant in the kidneys and lymphoid tissues INSIDE THE NUCLEUS
2. virus is reactivated when cellular immunity is suppressed
3. variety of neurologic deficits (visual loss, paralysis, dementia) evolving rapidly -> death
- nuclei of infected oligodendrocytes are packed with viral particles -> ground glass appearance
46
Leukodystrophies w/ an example:
- caused by mutations of genes involved in turnover, or maintenance of myelin - > altered metabolism of myelin- associated lipids
- eg. Krabbe disease
47
Krabbe disease:
- aka globoid leukodystrophy
- Autosomal recessive
- Deficiency of galacto/cerebro/sidase (enzyme for required for the catabolism of galactocerebroside)
- Consequence: an alternative catabolic pathway shunts galacto/cerebro/side to galacto/sylsphingosine which is cytotoxic -> loss of myelin and oligodendrocytes
- Globoid cells are hisiocytes filled with galactocerebroside
48
Central pontine myelinolysis
- pontine = in pons
- loss of myelin in the basis pontis in a symmetric pattern (Symmetric demyelination of the basis pontis, the CENTER)
- patient comes to you dehydrated and w/ low Na+ -> if you give them IV fluid and Na+ is RAPIDLY corrected you will get this disease, that's why it is iatrogenic
- aka osmotic demyelination syndrome
- rapid increases in osmolality damage oligodendrocytes
- rapidly evolving quadriplegia (paralysis of 4 limbs)
- “locked-in” syndrome
