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AFIFI > MESENCEPHALON > Flashcards

MESENCEPHALON Flashcards

1
Q

________ is a mixture of gray and white matter dorsal to the central gray matter.

A

TECTUM

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2
Q

________ refer to the basal portion of the mesencephalon, which includes the cerebral peduncle and substantia nigra.

A

BASIS PEDUNCULI

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3
Q

________ level is characterized in histologic sections by the decussation of the superior cerebellar peduncle and by the fourth nerve (trochlear) nucleus. T

A

INFERIOR COLLICULI

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4
Q

__________ is characterized by the red nucleus, the third nerve (oculomotor) nucleus, and the posterior commissure.

A

SUPERIOR COLLICULUS

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5
Q

Afferent connections of the tectum

A 
Lateral lemniscus. 
Contralateral inferior colliculus.
Ipsilateral medial geniculate body
Cerebral cortex
Cerebellar cortex via the anterior medullary velum.
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6
Q

Efferent Connections of the tectum

A

Medial geniculate body via the brachium of the inferior colliculus
Contralateral inferior colliculus.
Superior colliculus.
Nucleus of the lateral lemniscus and other relay nuclei of the auditory system for feedback.
Cerebellum

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7
Q

Fibers in the medial lemniscus are somatotopically organized, with ______ fibers being most medial and ____l fibers most lateral.

A

cervical, sacral

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8
Q

The __________ is composed of the ventral secondary trigeminal tracts and travels close to the medial lemniscus on its way to the thalamus.

A

trigeminal lemniscus

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9
Q

_________ conveys fibers from the basal ganglia and midbrain to the inferior olive and occupies a dorsal position in the tegmentum, ventrolateral to the medial longitudinal fasciculu

A

CTT

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10
Q

fibers thru mesencephalon

A 
Brachium conjunctivum (superior cerebellar peduncle)
ML
TL
ST
LL
MLF
RS
CTT
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11
Q

It contains unipolar neurons with axons (the mesencephalic root of the trigeminal nerve) which convey proprioceptive impulses from the muscles of mastication and the periodontal membranes.

A

mesencephalic n.

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12
Q

reasons why trochlear nucleus is unique

A

It is the only cranial nerve that crosses before emerging from the brain stem, and it is the only cranial nerve that emerges on the dorsal aspect of the brain stem.

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13
Q

Actions of the SO

A

primary of intorsion, secondary of depression, and tertiary of abduction

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14
Q

. Neurons of the__________ are affected in patients with progressive supranuclear palsy,

A

pedunculopontine nucleus

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15
Q

__________serotonergic fibers to the substantia nigra, neostriatum (caudate and putamen), and neocortex.

A

Nucleus Supratrochlearis (Dorsal Raphe Nucleus)

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16
Q

The medially located corticopontine fibers constitute the _____ projection; the laterally located fibers constitute the ____projections

A

frontopontine

parieto-occipito-temporo-pontine

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17
Q

The SN is composed of two zones: a dorsal zona compacta containing ___pigment and a ventral zona reticulata containing ____ compounds

A

melanin, iron

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18
Q

Nonpigmented neurons contain:

A

GABA, Ach

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19
Q

Afferent connections to the striatum

A 
Neostriatum: GABA
Cerebral cortex
GP: GABA
STN: Glutamine
 Tegmentonigral Tracts
 serotonin and cholecystokinin,
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20
Q

Efferent connections to the striatum

A

Nigrostriate: from the pars compacta project to the neostriatum
Nigrocortical Tract: medial zona compacta and the adjacent ventral tegmental area, course through the medial forebrain bundle, and terminate in the limbic cortex
Nigropallidal Tract
Nigrorubral Tract
Nigrosubthalamic Tract
Nigrothalamic Tract
Nigrotegmental Tract and Nigrocollicular Tract
Nigroamygdaloid Tract

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21
Q

two other cell groups in the mesencephalic tegmentum are dopaminergic

A

ventral tegmental area of Tsai

retrorubral cell group

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22
Q

hyperactivity in the _______ subdivision is believed to play a role in the symptomatology of psychotic disorders, whereas a reduction in function may contribute to the cognitive abnormalities found in patients with Parkinson’s disease.

A

mesoallorcortical pathway

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23
Q

decrease in dopamine in this system may explain cognitive impairments in patients with Parkinson’s disease. A decrease in dopamine in the visual cortex has been implicated in photosensitive epilepsy

A

mesoneocortical system

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24
Q

types of response mode have been demonstrated in mesencephalic dopamine neurons: (1) a ____ response to reward and reward-predicting stimuli that have to be processed by the subject with high priority and (2) _____ mode response involved in maintaining states of behavioral alertness

A

phasic, tonic

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25
Q

The ________is a laminated mass of gray matter that plays a role in visual reflexes and control of eye movement.

A

superior colliculus

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26
Q

Afferent of SC

A

cortex: Fibers originating from the frontal lobe are concerned with conjugate eye movements and reach the superior colliculus by a transtegmental route.
retina: bilateral, with a preponderance of contralateral input.
Spinal cord: conveys pain sensation.
inferior colliculus: turns the neck and eyes toward the source of a sound.

27
Q

Efferent tracts

A

Tectospinal tract: They are concerned with reflex neck movement in response to visual stimuli.
Tectopontocerebellar tract
Tectoreticular tract
Tectothalamic tract

28
Q

This area is an important station in the reflex pathway for the pupillary light reflex and vertical gaze.

A

pre-tectal area

29
Q

Parinaud’s components

A

vertical gaze palsies,
pupillary abnormalities (anisocoria, light-near dissociation),
conversion retraction nystagmus, lid retraction (Collier’s sign),
inappropriate conversion (pseudoabducens palsy),
impaired convergence,
skewed eye deviation in the neutral position,
papilledema, and
lid flutter.

30
Q

Components of the red nucleus

A

It is composed of a rostral, phylogenetically recent small cell part (parvicellular) and a caudal, phylogenetically older large cell part (magnicellular).

31
Q

Fiber system traversing red nucleus

A

(1) the superior cerebellar peduncle (brachium conjunctivum), (2) the oculomotor nerve (cranial nerve III) rootlets, and (3) the habenulointerpeduncular tract

32
Q

Interruption of the ______system results in a volitional type of tremor that is manifested when the extremity is in motion (e.g., attempting to reach for an object).

A

cerebello-rubral

33
Q

The triangular area bounded by the red nucleus, the inferior olive (in the medulla oblongata), and the dentate nucleus of the cerebellum is known as ___________

A

Mollaret’s triangle

34
Q

Corticorubral fibers arise mainly from the motor and premotor cortices and project mainly to the _______ red nucleus.

A

ipsi

35
Q

Efferent connections of RN

A

Rubrospinal: the rubro-spinal tract facilitates flexor motor neurons and inhibits extensor motor neurons.
rubrocerebellar: collaterals from the rubrospinal tract.
Rubroreticular fibers: offshoots from the rubrospinal tract
rubro-olivary tract

36
Q

Oculomotor nucleus receives from

A

mesen
pons, medulla
cerebellum

37
Q

Origin of Mesencephalic projections to the oculomotor nucleus

A

Cajal’s interstitial nucleus, the rostral interstitial nucleus of the medial longitudinal fasciculus (RiMLF), and the pretectal olivary nucleus: PLR

38
Q

paralysis of upward gaze.

A

Cajal’s interstitial nucleus (CONTRA)

39
Q

paralysis of downard gaze

A

the rostral interstitial nucleus of the medial longitudinal fasciculus (RiMLF_(IPSI)

40
Q

Pontine and medullary projections to the oculomotor nucleus arise from:

A

the vestibular nuclei, the nucleus prepositus, and the abducens nucleus.

41
Q

_______ to the somatic motor cell column arise from the contralateral dentate nucleus and are concerned with the regulation of eye movements

A

Cerebello-oculomotor fibers

42
Q

functions of the PAG

A

vocalization, control of reproductive behavior, modulation of medullary respiratory centers, aggressive behavior, and vertical gaze, UB fillings, penile erection (hypothalamus, rostral medulla)

43
Q

Afferent pathway of PLR

A

optic nerve —– optic tract ——- pretectal area—- posterior commissure —–Edinger-Westphal nuclei in the oculomotor complex.

44
Q

Efferent pathway of PLR

A

EWN—-cilliary ganglion—–short ciliary nerves—–sphincter pupillae and ciliaris muscles.

45
Q

A consensual light reflex is possible because of the projection ________ to both oculomotor nuclei.

A

pretecta;

46
Q

Marcus Gunn phenomenon

A

paradoxical dilatation of both pupils that occurs when light is shone in the symptomatic eye (optic nerve lesion)

47
Q

Pathway for MGP

A

The oculomotor nucleus senses the less intense light and shuts off the parasympathetic response, resulting in paradoxical pupillary dilatation

48
Q

Adie’s pupil,

A

is characterized by a widely dilated pupil and a sluggish, prolonged pupillary contraction in reaction to light. When it is constricted, the pupil takes a long time to dilate. T

49
Q

Pathology of Adies

A

pathology in the ciliary ganglion within the orbit.from redirection of regenerating parasympathetic fibers.

50
Q

Innervation of the ciliary ganglion

A

Normally, 90 percent of parasympathetic nerves in the ciliary ganglion innervate the ciliary body and the remaining 10 percent innervate the iris sphincter.

51
Q

accommodation-convergence reflex involves the following processes:

A
  1. assumption of a convex shape by the lens is secondary to contraction of the ciliary muscle,
  2. Contraction of both medial recti muscles for convergence brings the eyes into alignment.
  3. Pupillary constriction occurs as an aid in regulating the depth of focus for sharper images.
52
Q

nucleus has been assumed to play a role in convergence

A

Perlia’s

53
Q

Pathway of the accommodation-convergence

A

that afferent impulses from the retina reach the occipital cortex

and that the efferent pathway from the occipital cortex reaches the oculomotor complex after synapsing in the pretectal nucleus and/or superior colliculus

54
Q

Important for vertical gaze

A
  1. Motor neurons in the oculomotor (cranial nerve III) and trochlear (cranial nerve IV) nuclei that supply ocular muscles
  2. RiMLF. This nucleus constitutes the neural substrate for vertical eye movements
  3. Interstitial nucleus of Cajal (INC)
  4. Post com
  5. Nucleus of Post com
  6. MLF
55
Q

Lesions of the RIMLF

A

Bilateral: Vertical gaze paralysis

Unilatera;: down gaze paralysis

56
Q

explanation for Lesions of the RIMLF

A

bilateral projections of the nucleus to elevator motor neurons and ipsilateral projections to the depressor motor neurons.

57
Q

neural integrator for vertical gaze

A

INC

58
Q

Because of the projections of the INC to ocular motor neurons (cranial nerves III and IV) and to the opposite INC via the posterior commissure, the result of the INC lesion is

A

bilateral lesion.

59
Q

Commands for saccadic eye movements from which cerebral cortex part

A

The frontal eye field (area 8 in the frontal lobe), the angular gyrus (area 39), and the adjacent area 19 of the parieto-occipital cortices project to the superior colliculus.

the superior colliculus in turn projects to the brain stem pulse generators in the pons and midbrain.

60
Q

two pathways concerned with saccadic movements

A

anterior pathway from the frontal eye fields directly and indirectly (via the superior colliculus) to the brain stem centers for saccadic movements (PPRF for horizontal saccades and the mesencephalic RiMLF for vertical saccades)

a posterior pathway from the parieto-occipital cortex to the superior colliculus and then to the brain stem centers for saccadic movements

61
Q

The anterior pathway generates ____ saccades; the posterior pathway generates _____ saccades.

A

intentional,reflexive

62
Q

Specific lesions in the_________ that are associated with smooth pursuit deficits in humans correspond to Brodmann areas 19, 37, and 39.

Lesions in the _____also have been associated with deficits in smooth pursuit.

A

temporo-occipito-parietal cortex,

FEF

63
Q

Blood supply of the MB

  1. inferior colliculus (lower midbrain),
  2. lateral region of the midbrain
  3. which includes the trochlear nucleus, the cerebral peduncle, and the medial part of the medial lemniscus
  4. medial zone of the superior colliculus, which includes the third cranial nerve nuclear complex,
  5. tectum (dorsal zone)
  6. rest of MB
  7. upper midbrain (the pretectal level)
A
  1. paramedian
  2. SCA
  3. inconstant
  4. tip of basilar artery
  5. SCA
  6. posterior cerebral artery
  7. paramedian branches of the basilar art

AFIFI (24 decks)

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