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Anatomy 2 > CN 1-6 > Flashcards

CN 1-6 Flashcards

1
Q

Fasiculations

A

spontaneous contractions of small groups of muscle fibers that can be visible at the skin surface. Fibrillations are contractions of individual muscle fibers that can not be seen visually but are detected using electrical monitoring

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2
Q

Clonus

A

rapid series of alternating muscle contractions that occur in response to the sudden stretch of a muscle.

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3
Q

Corticospinal tract (CST)

A

Originates in cerebral cortex, precentral gyrus and nearby areas
Descends thru cerebral peduncle, basis pontis, medullary pyramid, decussates at spinomedullary junction

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4
Q

CN 1

A

Axon type: SSA
CNS origin or termination: Olfactory bulb
Peripheral origin or termination: olfactory epithelium

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5
Q

CN 2

A

Axon type: SSA
CNS origin or termination: Lateral geniculate nucleus (in thalamus), superior colliculus, hypothalamus

Peripheral origin or termination: Lateral geniculate nucleus (in thalamus), superior colliculus, hypothalamus

Originates in eye, goes to thalamus. Relay nuclei for vision.

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6
Q

CN 3

A

Axon type: GSE
CNS origin or termination: Oculomotor nucleus

Peripheral origin or termination: Superior, inferior, medial recti; inferior oblique, levator palpebrae superioris muscles

Axon type: GVE
CNS origin or termination: Edinger-Westphal nucleus (in above)

Peripheral origin or termination: Ciliary ganglion, Sphincter pupillae muscle

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7
Q

CN 4

A

Axon type: GSE
CNS origin or termination: Trochlear nucleus

Peripheral origin or termination: Superior oblique muscle

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8
Q

CN 6

A

Axon type: GSE
CNS origin or termination: Abducens nucleus

Peripheral origin or termination: Lateral rectus muscle

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9
Q

Olfaction

A

Taste & smell: conscious chemical sensation
Olfaction: detects volatile chemicals (odorants) drawn into nasal cavity
Humans can detect about 10,000 different odors

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10
Q

Olfactory epithelium

A

Peripheral origin of olfactory system

Patch in roof of nasal cavity, bilateral

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11
Q

Olfactory epithelium contains

A

3 million receptor cells,
Bowman’s gland ducts,
Sensory endings from CN V (irritants)

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12
Q

Olfactory receptor

A

A small bipolar neuron
Dendrite ends in olfactory vesicle, from which 10-30 cilia spread over the surface in a layer of mucus secreted by Bowman’s glands

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13
Q

Olfactory receptor stimulates

A

chemosensitive cilia

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14
Q

Olfactory receptor lifespan

A

Replaced throughout life; lifespan 1-2 months

Unusual among human neurons

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15
Q

Axons from olfactory receptors

A

among thinnest and slowest

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16
Q

Collect into a series of bundles (only about 20) called

A

olfactory fila, pass thru holes in cribriform plate of ethmoid bone

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17
Q

Olfactory fila make up

A

CN1, Synapse on 2nd order neurons in olfactory bulb

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18
Q

Olfactory bulb & tract

A

Develops as an outgrowth of telencephalon

Tract reaches ipsilateral hemisphere with no relay in thalamus

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19
Q

Olfactory fibers sort in

A

bulb

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20
Q

Each type of olfactory receptor (different colors) sends an axon to one

A

glomerulus of a mitral cell even though these cells are intermingled in the olfactory epithelium

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21
Q

Olfactory tract made up of axons from

A

mitral and tufted (not shown here) cells

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22
Q

Olfactory bulb projections - Collaterals to

A

anterior olfactory nucleus (1)

Thought to regulate sensitivity of olfactory bulb

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23
Q

Olfactory bulb projections - Fibers project to

A 
both bulbs (red)
Cross midline in anterior commissure, which is in the brain and not on the surface as depicted here
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24
Q

Lateral olfactory stria:

A

lateral (primary) olfactory area

Medial olfactory stria Cortex over uncus, entorhinal area, limen insula, amygdala
Pyriform area: uncus, entorhinal area, limen insula

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25
Q

Medial olfactory stria

A

to medial (secondary) olfactory area
Subcallosal region of medial frontal lobe surface
Emotional response to smell

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26
Q

Intermediate olfactory stria

A

Rudimentary in humans

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27
Q

Limen insula

A

refers to the junction point between the cortex of the insula and the cortex of the frontal lobe

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28
Q

Olfactory information sent to….

A

Hypothalamus, thalamus, hippocampus, orbital cortex, amygdala
Direct projections and a thalamic relay: DMN to…
Olfactory association cortex: orbital surface of frontal lobe and anterior insula (near taste)
Ipsilateral

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29
Q

Cornea and lens focus image on

A

retina

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30
Q

Focus requires

A

refraction of light

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31
Q

Lens accounts for about a

A

third of the eye’s refractive power
Major role in adjusting focus for near/ far objects
Most refraction is in air-water interface at corneal surface

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32
Q

Iris

A

Affects brightness and quality of image focused on retina

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33
Q

Pupil size controlled by 2 smooth muscles in iris

A

1)Pupillary sphincter: encircles pupil, stronger than dilator

Smaller pupil improves ocular performance (like small aperture size improves camera lens performance)

2) Pupillary Dilator: arranged in radiating spokes from the pupil

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34
Q

Rods & Cones: Photoreceptors

A

Highly specialized cells with different structural regions

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35
Q

Rod and cones outer segement

A

contain visual protein

Photons absorbed here cause receptor potential

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36
Q

Rods

A

rhodopsin

Low-acuity; monochromatic vision in dim-light

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37
Q

Cones

A

Cone pigments

High-acuity, color vision, need a lot of light

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38
Q

Retinal structure -1st synapse layer

A

terminate on bipolar & horizontal cells

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39
Q

Retinal structure - Bipolar cells project to 2nd synapses

A

horizontal cells spread laterally interconnect receptors, bipolar cells, horizontal cells

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40
Q

Bipolar cells terminate on

A

ganglion cells and amacrine cells; amacrine cells interconnect bipolar cells, ganglion cells and other amacrine cells

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41
Q

Ganglion cell axons in optic nerve travel to

A

Optic chiasm, partial decussation
Enter optic tract
Most travel to lateral geniculate nucleus (LGN); thalamic relay for vision
Others go to superior colliculus, hypothalamus
From LGN to primary visual cortex in banks of calcarine sulcus of occipital lobe

42
Q

Fibers from nasal half of retina cross to

A

contralateral optic tract

43
Q

Fibers from temporal half of retina enter

A

ipsilateral optic tract

So each optic tract “sees” the contralateral visual field

44
Q

Depth perception

A

Need to examine comparable areas of both retinas, which is accomplished by chiasm

45
Q

LGN: Structure

A

-layered, precise retinotopic arrangement
Pattern is the same in each LGN layer so any given point in the visual field is represented as a 6 layered cell column in LGN
Each layer gets input from one eye
1, 4 & 6 contralateral eye
2, 3 &5 ipsilateral eye

46
Q

LGN projects to

A

primary visual cortex

Fibers representing inferior visual fields most superior in radiations
Those representing superior visual fields, most inferior in radiations

47
Q

Superior colliculus

A

Optic tract fiber bypass LGN go to superior colliculus & pretectal area (junction of midbrain and diencephalon)
Also primary visual cortical projections to superior colliculus

48
Q

Hypothalamus

A

Suprachiasmatic nucleus, gets direct retinal input
Master timer of circadian rhythm
Daily body temperature changes, hormone secretion, eating, drinking

49
Q

anopia or –anopsia

A

denote loss of one or more quadrants of visual field

50
Q

Hemianopia

A

loss of half a visual field

51
Q

Quadrantanopia

A

loss of one quarter of a visual field

52
Q

Homonymous

A

similar visual field lost in each eye

53
Q

Heteronymous

A

two eyes have non-overlapping visual field loss

54
Q

Visual field deficits

A

Damage anterior to chiasm only affects ispilateral eye
Damage at chiasm causes heteronymous deficits
Damage to optic tract causes homonymous deficits

55
Q

Superior rectus

A

CN 3, Elevation for eye

56
Q

Inferior rectus

A

CN 3, depression

57
Q

Medial rectus

A

Adduction CN3

58
Q

Inferior oblique

A 
External rotation (Extorsion 
CN3
59
Q

Superior oblique

A

CN4, Internal rotation (Intorsion) downward & lateral

60
Q

Lateral rectus

A

CN4, Abduction

61
Q

III nucleus consists of

A

multiple columns of neurons that supply each muscle

62
Q

Parasympathetic input to the eyes

A

Pupillary
constrictor
muscle

63
Q

Pupillary light reflex

A

Constriction of pupils in response to light involves four sets of neurons

64
Q

Pregang. Parasym. fibers in III nerve

A

synapse in ciliary ganglion

65
Q

Each pretectal nucleus is linked to

A

both EWN, via the posterior commissure

66
Q

Afferent limb

A

retinal ganglion cells to pretectal nuclei

67
Q

Postgang. fibers in

A

short ciliary nerves, enter iris, supply sphincter (constrictor) of pupillae

68
Q

Accommodation (the near response)

A

Lens flat at rest due to tension on its capsule exerted by the suspensory ligament
To view an object close up: ciliary muscle contracts, which relaxes lens suspensory ligaments and lens bulges (thickens)
Sphincter pupillae contracts
Decrease light coming though lens periphery (which is thinner)

69
Q

Convergence - accommodation

A

visual axis of both eyes converge due to increased tone in medial rectus muscles

70
Q

Sympathetic input to the eyes - Central fibers from hypothalamus

A

cross midline in midbrain join ipsilateral descending fibers in pons and medulla

71
Q

Preganglionic fibers emerge in first

-sympathetic input to eyes

A

thoracic ventral nerve root and ascend sympathetic chain to SCG

72
Q

Postganglionic fibers run along

-sympathetic input to eyes

A

external and internal carotid arteries and their branches

Fibers leave IC, join Vi in cavernous sinus, then to ciliary nerves

73
Q

Results of III injury

A

The affected eye is “down and out”
Eye ipsilateral to lesion deviates laterally
Medial rectus is weak and lateral rectus is unopposed, lateral strabismus
Patient cannot move the eye medially, weak medial rectus
Vertical movement impaired, weak superior and inferior recti and inferior oblique ipsilaterally
Diplopia: double vision
Ipsilateral levator palpebrae superioris weak: ptosis

74
Q

Mydriasis

A

pupil on affected side is dilated
Pupillary dilator is unopposed as pupillary sphincter and ciliary muscle are dysfunctional
Pupil does not constrict in response to light

Lens cannot be focused for near vision

75
Q

Trochlear nerve (IV) - axons

A

leave the nucleus and course dorsally, decussate and exit brainstem on dorsal surface- only cranial nerve to do so

76
Q

Results of IV injury

A

Superior oblique moves eye downwards and laterally

77
Q

IV deficits much less noticeable than III deficits

A

Affected eye points up a bit, head tilts away from lesion
e.g. A right palsy results in a head tilt to the left this lines up the normal eye with the extorted affected eye
Patients report diplopia when going downstairs or reading

78
Q

CN IV

A

Innervates ipsilateral lateral rectus, which abducts eye

79
Q

CN IV in

A

floor of 4th ventricle, caudal pons

80
Q

Medial to VI nucleus are the

A

MLF and motor fibers of VII

81
Q

Internal genu of VII nerve:

A

site where fibers wrap around and turn to exit

82
Q

VI nucleus and internal genu

A

facial colliculus

83
Q

IV nerve injury

A

medial strabismus (affected eye deviated medially)

84
Q

Both eyes work together during gaze

A

Look laterally to one side requires ipsilateral rectus and the contralateral medial rectus to contract simultaneously

85
Q

Medial longitudinal fasciculus (MLF)

A

allows coordination of head and eye movement

86
Q

MLF interconnects

A

III, IV & VI nuclei to allow this

87
Q

III, IV & VI nuclei contain motor neurons and

A

internuclear neurons that ascend in MLF

88
Q

MLF injury results in…

A

Internuclear ophthalmoplegia

“paralysis of the eye due to damage between the nuclei”

89
Q

MLF damage removes

A

excitatory input to ipsilateral III nucleus

90
Q

Eye ipsilateral to lesion fails to

A

move past midposition during horizontal gaze

91
Q

Both VI nuclei are intact so

A

lateral movements of both eyes are intact

92
Q

Control of eye movements -3 main movements

A

Scanning, tracking, compensation

93
Q

Scanning

A

Scanning: eyes move from one visual target to another in high-speed movement know as saccades

94
Q

Tracking

A

a.k.a, smooth pursuit, eyes follow area of interest across visual field

95
Q

Compensation

A

gaze held on object of interest during head movement, known as vestibulo-ocular reflex (vestibular system also at work)

96
Q

Gaze centers

A

in brainstem reticular formation

97
Q

Horizontal saccades

A

paramedian pontine reticular formation (PPRF), each pulls eye to its own side

98
Q

Upward saccades

A

midbrain, rostral interstitial nuclei of the MLF (riMLF)

99
Q

Downward saccades

A

in midbrain next to upward center

100
Q

Pathways involved in voluntary saccade to the left.

A
  1. Projection from right frontal eye field activates left paramedian pontine reticular formation (PPRF).
  2. Some PPRF neurons activate adjacent abducens neurons
  3. Other PPRF neurons send heavily myelinated (fast) internuclear fibers along the medial longitudinal bundle to activate oculomotor neurons serving medial rectus.
101
Q

Simultaneous contraction of the respective rectus muscles

A

yields a saccade to the left.

102
Q

78 year old male who had a stroke
He is weak on the right side of his body and needs assistance to get into the dental chair
The left eye is deviated inward and he cannot move that eye outward
Where is this patient’s lesion?

A

Left corticospinal tract lesion in pons. Abducens nerve issue, not an abducens nucleus (interneurons and would affect gaze). Also, that would be a massive lesion.

Anatomy 2 (15 decks)

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