Flashcards in Visual Pathway Deck (67)
Which part of the eye contains no photoreceptors?
The optic disc.
-blind spot on retina
Where is the optic disc located?
On the retina, medial to the fovea.
What is the retina?
The nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve.
What are the 2 layers of the retina?
What does the non-neuronal layer of the retina consist of?
-sits against the choroid of the eyeball and absorbs photons
What are photons?
Particles of light energy.
What is the function of the pigmented epithelium?
Surrounds photoreceptors via melanin-filled microvilli.
-maintains their metabolic activity
What does the neuronal layer of the retina contain? (4)
What do photoreceptors do?
Receive photons and convert them into signals.
What are the 2 types of photoreceptors?
Why does light have to pass through other fibres to get to photoreceptors?
Decreases the intensity of light reaching the retina.
What do bipolar neurons do?
Connect photoreceptors to ganglionic cells.
What do ganglionic cells combine to form as they leave the retina?
The optic (II) nerve.
What is the function of interneurons?
Interconnect photoreceptors/bipolar neurons/ganglionic cells.
-modulate transmission and sharpen information to the cortex
What are the 2 types of interneuron?
Where are horizontal interneurons located?
At the level of photoreceptors and bipolar neurons.
Where are amacrine interneurons located?
At the level of bipolar neurons and ganglionic cells.
What process occurs in the neuronal layer of the retina?
Photochemical reactions tranduce photons (light energy) to electrical energy.
How many neurons are there from the retina to the cortex?
What is the pathway of light energy from the retina to the cortex?
>> 1* BIPOLAR CELLS
>> 2* GANGLIONIC CELLS
>> Lateral geniculate nucleus (thalamus)
>> 3* OPTIC RADIATION
>> 1* visual cortex (cerebral cortex)
>> Association centre
What is the optic nerve an outgrowth of?
-part of the CNS
What membranes surround the eyeballs?
What effect can increased CSF/ICP have on vision?
Can cause the optic nerve to swell and compress the retinal central vein >> PAPILLOEDEMA.
-lifts retina away from the pigmented epithelium
What is papilloedema?
Optic disc swelling due to increased ICP.
>> headache, drowsiness, blurred vision
Which part of the thalamus does the visual pathway go to?
Lateral geniculate nucleus.
NB. Which part of the thalamus does the auditory pathway go to?
Medial geniculate nucleus.
Where does vision from the same area of the visual field travel?
Enters different eyes, but travels down the same optic tracts.
Where does the medial (nasal) retina send information to?
The contralateral thalamus.
Where does the lateral (temporal) retina send information to?
The ipsilateral thalamus.