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Year 2 Anatomy > Eye & Cerebellum > Flashcards

Eye & Cerebellum Flashcards

1
Q

What are the outermost layers of the eye? Describe them

A

three layers to the eye inc:

sclera: thick protective outermost layer
choroid: vascular layer
retina: contains retinal pigment epithelium and photoreceptors

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2
Q

Which part of the eye contains the most amount of cones? Label it on this diagram

A

Fovea centralis, light from the cornea is also refracted onto this structure

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3
Q

Label and describe the remainder of this diagram

A

The eye is filled with vitreous humour in the vitreous body- this is for structural support
Cornea refracts light into the eye

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4
Q

The eyes lie in the bony orbits. Describe these

A

Each orbit has a square base, superolateral to the piriform aperture (‘nose hole’)
The orbital margins v strong superiorly and laterally to protect the eyes. But the medial wall= thin and delicate

The orbit has 4 walls: superior, inf., medial, lateral
7 bones of the skull contribute to these walls (the 6 in the diagram + nasal bone)

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5
Q

Label this

A
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6
Q

What is this v shaped structure?

A

This V shaped structure is the orbital fissure it has a superior part (highlighted) and inferior part.
there are two distinct parts because different structures pass through the superior and inferior part of the orbital fissure.

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7
Q

What is the origin of the extra occular muscles?

A

The Annulus of Zinn: ring of fibrous tissue surrounding the entrance of the optic nerve
It encloses part of the sup.orbital fissure
The extraocular muscles originate from the annulus of zinn (in green) except for the inf + sup. oblique.

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8
Q

Which nerves pass through the annulus?

A
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9
Q

Six extraocular muscles move the eye. What are they?

A
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10
Q

Label this

A
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11
Q

There is also an eyelid elevator. What is this and explain why sometimes the eyelid can droop in a stroke

A

There is also an eyelid elevator, levator palpabrae superioris – this is mainly voluntary striated muscle.
Innervated by cranial nerve III (oculomotor nerve). In 3rd cranial nerve lesions you can have a ptosis where the eyelid droops.

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12
Q

Describe the extraoccular muscles

A

The sup. rectus originates from the annulus of Zinn. elevate, adduct and intorts eyeball

Inf. rectus extort, depress and adducts eyeball

Sup.oblique runs through a pulley (trochlea) structure on the medial orbit. Depresses, abducts, intorts the eye.
Inf. oblique originates from maxilla surface. Elevate, extort and abduct eyeball

Medial rectus: eye adduction
Lateral rectus: eye abduction

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13
Q

What is the innervation for the extraoccular muscles?

A

ALL cranial nerve III, except:
Superior oblique: 4th cranial nerve (trochlear)
Lateral rectus: 6th cranial nerve (abducens).

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14
Q

Describe the retinal layers

A

Layers 1-9, 9 being most deep
Rod cells are throughout the retina, whereas cones are found closer to the fovea
The output is via the nerve fibre layer, and this means that it can be easily damaged in high intraocular pressure states such as glaucoma.

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15
Q

What is the Uveoscleral outflow pathway? What happens if this pathway gets blocked?

A

Aqueous humor produced by the ciliary body passes out of the anterior chamber via the trabecular meshwork & schlemm canal.

If this is blocked it can lead to glaucoma + raised intraocular pressure.

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16
Q

Describe the fovea

A

On the temporal side of the optic disc, opposite the pupil is a yellow area called the macula lutea. At the middle of the macula is the fovea centralis/fovea.

Fovea= many cones and accounts for the majority of the visual afferent stimuli that is transmitted to the brain.

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17
Q

Describe the optic nerve pathway

A

The ganglionic cells aggregate at the optic nerve which passes out of the orbit via the optic canal, encased in dura.
The nasal fibers then cross at the optic chiasm, temporal fibres remain on the same side.

18
Q

What is the role of nasal fibres?

A

Nasal fibres carry info about the temporal aspect of your visual field.
This is why lesions at the optic chiasm mostly affect these nasal fibres and give rise to bitemporal hemianopia

19
Q

Describe pretectal synapses in the light reflex

A

If light has shone into one eye, the impulse is transmitted by the optic nerve.
Impulse passes into the midbrain–>pretectal nucleus–> Edinger-westphal nucleus (a parasymp nucleus for CNIII) -> innervates ciliary body + iris to cause pupil constriction.

20
Q

What is the consensual reflex?

A

When you shine light into one eye, the other eye will also constrict
This is a consensual light reflex. And this is because the pretectal nucleus on one side synapses w the e.westphal nucleus on both sides= bilateral efferent reaction

21
Q

Describe the accomodation reflex

A
22
Q

What is the Lateral geniculate nucleus?
where r they located?

A

Laterally & inferiorly on either side of the diencephalon are the lateral geniculate bodies.
There are two types of cells - magnocellular and parvocellular found in the geniculate nucleus where the optic tracts synapse.
This generates neurons which project directly to the primary visual cortex.

23
Q

Complete this diagram to show the visual pathways

A
24
Q

Describe the anatomy of the cerebellum, using this posterior diagram to distingish between the different lobes

A
25
Q

In the anatomy of the cerebellum from an anterior view, describe the retrotonsillar fissure and the tonsils. What is a pathological example to do with one of these structures?

A

Retrotonsillar fissure- separates the tonsils from the rest of the cerebellum
Tonsils (green) can pathologically descend thru the f.magnum= Chiari malformation

26
Q

On the anterior cerebellum, point out the following structures:
Biventral lobe, flocculondular lobe, flocculus, sup. Peduncle, middle and inferior peduncle

A

they attach the cerebellum to the brainstem and give rise to various pathways

27
Q

How is the cerebellum related to the fourth ventricle?

A

The cerebellum covers the brainstem and creates the cavity that is the fourth ventricle. Remember CSF drains via the aqueduct of sylvius which drains into the fourth ventricle

28
Q

Describe the layers of the cerebellar cortex, in particular the purkinje cells

A

Split into 4 layers: molecular, purkinje, granule, white matter

Sole and main output of the cc is via the purkinje cells
These are v large cells within the cc and dendrites They extend into the molecular layer to form synapses w other neural cells -mainly granule cells
- P cells are inhibitory in nature (release GABA)
- various targets (primarily the cerebellar nuclei)
- efferent cell of cerebellum and main one of the cc

29
Q

Describe cerebellar neural connections

A
30
Q

What are the principle cell types of the cerebellum?

A
  • Purkinje cells - travel into the deep cerebellar nuclei. These cells utilize GABA (inhibitory effect).
  • Mossy fibers - arise from pontine nuclei, as well as vestibular nuclei and from the spinal cord. These fibers form excitatory connections with the deep cerebellar nuclei.
  • Climbing fibers - arise from the inf. olivary nucleus and send collaterals to the deep nuclei before entering the cerebellar cortex.
31
Q

One of the functional aspects of the cerebellum is the dentate. What is the dentate nuclei?
inputs, output, 2 targets

A

Most output from the cerebellum arises from these dentate cerebellar nuclei
Receives input from lateral cerebellar hemisphere via mossy + climbing fibers + also receive GABA (inhibit) input from Purkinje cells

Output passes through the superior cerebellar peduncle + decussates in midbrain

targets: red nucleus - the thalamus en route to the cortex modulates cs tract + rubrospinal tract

32
Q

What are the globose & emboliform nuclei of cerebellum?
input & output

A

a

33
Q

describe fastigial cerebellar nuclei?
3 inputs, output

A

a

34
Q

What is the function of the globose nuclei?
input & output

A

fine tune coordination + help coordinate movement
fibres are sent from the spinocerebellar tract, by the inf peduncle - mossy fibres will then synapse on the two nuclei & granular cells - Granular cells excite the purkinje, and modulate their inhibitory effect on these 2 nuclei

From these fibres, you get your efferent fibres, which pass by the superior cerebellar peduncle to the end targets

35
Q

There are 3 functional divisions of the cerebluum. Describe the spinocerebellum
location, function, inputs & outputs

A

Spinocerebellum/paleocerebellum.
Consists of the lobes near the midline.

Monitor and fine-tunes limb movements. This is achieved by proprioceptive input from the dorsal column pathway, the cranial trigeminal nerve, the visual and auditory systems, & spinocerebellar tract.

Output–>deep cerebellar nuclei. These then project to the cerebral cortex, and brainstem. This enables the region to monitor & modify activity of descending motor pathways.

36
Q

There are 3 functional divisions of the cerebluum. Describe the cerebrocerebellum
location, input & output

A

(Cerebrocerebellum/neocerebellum.)

It consists of the lateral cerebellar lobes.
Receives info from the parietal lobe in cerebral cortex (primary sensory lobe of brain) with pontine nuclei in between

Output–>ventrolateral thalamus–>premotor cortex & primary motor area.

37
Q

There are 3 functional divisions of the cerebluum. Describe the vestibulocerebellum
function, 3 inputs, what happens if damaged?

A

Vestibulocerebellum/archicerebellum
Spatial awareness and balance.
Input from the vestibular nuclei, auditory and visual systems
If a patient has damaged this region=disturbed balance and gait.

38
Q

Describe the inferior cerebellar peduncles
location, input & output

A

a

39
Q

Describe the middle cerebellar peduncle
input & output

A

a

40
Q

Describe the Superior cerebellar peduncle:
input & output

A

a

41
Q

Describe cerebellar lesions:
compare vestibulo vs spino vs ponto lesions

A

a

42
Q

Differentiate between dyssynergy and dysmetria

A

dyssenergy → decompensation of movement (a complex movement is broken down into its own individual components)

dysmetria → mainfested when you ask a patient to touch an object in front of them, they overshoot the mark due to lack of coordination

Year 2 Anatomy (17 decks)

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