Visual pathway

Question 1

What are the 3 layers of the eye ball?

Answer 1

Sclera
Choroid
Retina

Question 2

What structure is in line with the visual axis?

Answer 2

Macula

Question 3

What does the Macula contain?

Answer 3

It contains Con cells that are invovled in high acuity vision

Question 4

What nerve controls the ciliary muscle?

Answer 4

The Ps branch of occulomotor nerve via the ciliary ganglion.
Post ganglion axon innervates the spincter pupilae via V1

Question 5

What does the retina contain?

Answer 5

Photoreceptors

Question 6

Does the optic disc contain photoreceptors and what is it attached to?

Answer 6

It does not contain photoreceptors it is a blind spot of the eye.
Connected to the optic nerve that goes to the optic chiasma

Question 7

What two layers can the retina be divided into?

Answer 7

The non neuronal layer ( pigmented) or the neuronal layer ( photoreceptors)

Question 8

What is the actions of the non neuronal layer of the retina?

Answer 8

It contains pigmented layer that sits against the choroid of the eye ball and is light absorbing. It absorbs any photons not absorbed by the photoreceptors to prevent blurred vision.

It also maintains metabolic activity of the photoreeptors which it surrounds by melanin filled microvilli

Finally it supplies the photoreceptors with capillaries

Question 9

What does the neuronal layer contain?

Answer 9

Contains photoreceptors, bipolar and ganglion neurones

Question 10

What does the bipolar neurone connect?

Answer 10

It connects the photoreceptors to the ganglion cells

Question 11

What do the axons of the ganglion cells form?

Answer 11

The axons of the ganglion cells form the optic nerve at the optic disc

Question 12

What is the location of the optic disc in relation to the fovea?

Answer 12

It is slightly medial

Question 13

What interconnects the photoreceptors, bipolar and ganglion cells?

Answer 13

Interneurones: horizontal and amacrine

Question 14

Where are the horizontal and amacrine interneurones situated?

Answer 14

The horizontal is between the photoreceptors and the bipolar cells

The amacrine is between the bipolar and amacrine cells

Question 15

What is the function of the interneurons?

Answer 15

They modulate transmission by turning off and on the photoreceptors –> control the acuity of vision.

Question 16

What is the change of energy at the interneurons?

Answer 16

Photochemical reaction occurs that see’s the transmission of transudece light enery to electricle energy.

There is a change in action potential

Question 17

What is odd about the retina and direction of light?

Answer 17

The light has to get throug the mesh of support to get to the photoreceptors

Question 18

What is abnromal about cranial nerve 1 and 2?

Answer 18

They are part of the CNS not the PNS

THe optic chiasma is attached to the floor of the hypothalamus which is a outgrowth of the diencephalon

Question 19

What is the eye balls a outgrowth of?

Answer 19

The diencephalon

Question 20

What is the route of the visual pathway? Retina to cortex?

Answer 20

1st and 2nd order are within the retina
First order unlike the others is very short –> Bipolar cells

2nd order: Ganglion cells the axons extend out of the retina into the optic disc where it forms the optic nerve.

The optic nerve ( formed within the CNS) goes to the lateral geniculate nucleus of the thalamus –> relay nuclei

The 3rd order is the optic radiate –> Goes from the thalamus to the primary visual cortex

Question 21

What surrounds the optic nerve and eye ball as a consequence of being a outgrowth of the CNS?

Answer 21

It is surrounded by meninges as the optic nerve extends to the eye ball.

Has the same layers and structure with CSF in the subarachanoid space

Question 22

What is the consequence if there is a rise in ICP of the CSF surrounding the eye ball and optic nerve?

Answer 22

Papilloedema

Question 23

How does Papilloedema arise?

Answer 23

There is a increase in CSF pressure which causes the compression of central retinal veins which prevents venous drainage of the eye.

This causes the swelling of the optic disc and therefore the compression of the optic nerve as well as that is surrounded by the menigines

Question 24

What is the symptoms of increase CSF pressure in the eye?

Answer 24

Blurred vision, drowsiness, head ache and vomiting

Question 25

Where is the primary visual area?

Answer 25

The occipital lobe | The calcarine sulcus

Question 26

What seperates the occipital and parietal lobe?

Answer 26

The parietooccipital sulcus

Question 27

What sits above and below the calcarine sulcus?

Answer 27

Striate cortex --> upper and lower bank of the calcarine sulcus

Question 28

Where is the visual assoication cortex?

Answer 28

It is the pre straite area and above and below the upper and lower bank of the calcarine sulcus

Question 29

Do you see the Calcarine sulcus mainly in the lateral or medial surface of the brain?

Answer 29

The medial surface

Question 30

What are the two visual fields?

Answer 30

``` Temporal and nasal Temporal is (lateral) Nasal ( down the middle) ```

Question 31

If you are looking left the light will hit what part of the left and right eye?

Answer 31

It will hit the nasal part of the left eye and the temporal part of the right eye

Question 32

If you are looking dead straight where will the light hit?

Answer 32

The macula

Question 33

If you are looking right the light will hit what part of the left and right eye?

Answer 33

The light will hit the nasal retina part of the right eye and the temporal retina part of the left eye

Question 34

From what direction does information cross to the contralateral side?

Answer 34

The information coming from the left or right temporal field

Question 35

Is the nasal fibers and temporal fibers run contralaterally or ipsilaterally?

Answer 35

The nasal fibers run contralaterally | The temporal fibers run ipsilaterally

Question 36

What part of the cerebral hemisphere does the left and right half of visual field go to?

Answer 36

The left half of the visual field goes to the right cerebral hemisphere The right half of the visual field goes to the left cereberal hemisphere

Question 37

What bank fo the calcarine sulcus does upper and lower vision field go to?

Answer 37

The upper vision field goes to the lower bank of the calcarine sulcus The lower vision field goes to the upper bank of the calcarine sulcus

Question 38

Where does center visual axis (macule) go to?

Answer 38

The occipital pole

Question 39

What is the route of the pathway from the LGN of the thalamus to the upper and lower banks of the calcarine sulcus?

Answer 39

They take different pathways to the banks. | There is a upper and lower visual field pathway.

Question 40

What is the Meyers loop?

Answer 40

Due to the position of the inferior horn of the lateral ventricle the lower visual field pathway has to loop around the inferior horn which is called the Meyer's loop

Question 41

How can vision be disrupted?

Answer 41

Damage to the vision pathway between the retina and the cerebral cortex

Question 42

What is the name of localised patches of blindness?

Answer 42

Scotoma

Question 43

What is anopia?

Answer 43

Referes to the loss of one or more quadrants of visual field

Question 44

What is hemianopia?

Answer 44

When there is loss of half the visual field

Question 45

What is the name of the condition when you loose quater of your visual field?

Answer 45

Quadrantanopia

Question 46

What is heteronymous?

Answer 46

Visual loss that is different on each side

Question 47

What is homonymous?

Answer 47

Visual field loss that is similar on each side

Question 48

What is homonymous heminopia?

Answer 48

It is the loss of half of your visual field on the similar side of each side

Question 49

What is monocular blindness?

Answer 49

Complete blindness in one eye

Question 50

In monocular blidness where is the lesion?

Answer 50

Lesion of the optic nerve

Question 51

Lesion of the optic chiasma will cause what type of visual field loss?

Answer 51

Heteronymous hemianopia | It is visual loss in the outer half of both the right and left eye

Question 52

What is homonymous hemianopia and what is the cause?

Answer 52

Is loss of vision on the same side of both eyes | Caused by a lesion of the optic tract--> complete lesion

Question 53

How do you get homonymous quadratanopia?

Answer 53

Damage to one of the fibers in the optic radiation

Question 54

10% of optic tract don't go to the LGN but to another structure. What structure is this?

Answer 54

10% take a medial root to the pre tectal area in the mid brain in front of the colliculus. Involved in pupillary light reflex

Question 55

What is the pupil light reflex?

Answer 55

The ability for both eyes to dilate or constrict depending on the level of the light the retina recieves

Question 56

What two cranial nerves are invovled in the pupil light reflex?

Answer 56

Afferent (sensory) root = optic nerve and tract | Efferent (motor) root = occulomotor nerve

Question 57

What are the two components of the pupil light reflex?

Answer 57

Direct component --> shine light in a eye and the same pupil constricts Consensual component --> shine light in one eye and the opposite pupil constricts

Question 58

What are the two nucleis of oculomotor nerve?

Answer 58

Oculomotor nuclei | Edinger Westphal nuclei

Question 59

What are the functional characteristics of Rod cells?

Answer 59

Highly sensitive to light ( specialised for night vision) High photopigment, capture a large amount of light High amplification Low temporal resolution ( slow response) More sensitive to scattered light

Question 60

What are the functional characteristics of Cone cells

Answer 60

``` Low sensitivity to light ( specialised for day vision) Less photopigments than rod cells Low amplification High temporal resolution ( fast acting) More sensitive to direct light ```

Question 61

What are the functional characteristics of rod system?

Answer 61

Low acuity, not found in the fovea and invoveld in converent pathway Achromatic only one type of rod cell

Question 62

What are the function characteristics of cone system?

Answer 62

High acuity and found in the Fovea. Invovled in divergent pathway Trichromatic, has 3 different types which have different wavelength preference

Question 63

What is the fiber that transfers information from the primary visual area ( straite cortex) to the secondary visual area ( prestraite area)?

Answer 63

Short assoication fibers

Question 64

Macula vesion goes to what part of the occipital?

Answer 64

The occipital pole

Question 65

Where would there be damage if there was homonymous heamianopia ( with macula sparing)

Answer 65

There would be damage to the optic radiate not going to the occipital pole

Question 66

If there was bilateral central scotoma what part of the visual pathway would be damaged?

Answer 66

The ocipital pole would be cut

Question 67

If you were going to have homonymous hemianopia ( with macula sparing) where would be the lesion?

Answer 67

The lesion would cut the optic radiate of both optic tracts but the occipital pole would remain intact.

Question 68

What nuclei does the optic nerve in the pre tectorial area synapse with?

Answer 68

The Edinger- Westphal nucleus on the ipsilateral and contralateral side

Question 69

If you damage the optic nerve of a eye would it stll be able to constrict?

Answer 69

Yes it would be because the occulomotor nerve is still intact and the other eye can cause the constriction to happen

Question 70

If there was damage ot the occumulotor nerve of one of the eyes would that eye be able to constrict?

Answer 70

No it would not be able to constrict as there is no way of getting PS information to the eye and therefore the eye would be slightly dilated as there as the sympathetic input is unopposed