5 –The visual system Flashcards
How many pairs of cranial Nerve do we have?
12 pairs
What makes cranial nerves 1 and 2 different?
They develop from the CNS
What is cranial nerve 1 an extension of?
Our telencephalon
What is cranial nerve 2 an extension of?
Our diencephalon
Describe the cornea
The clear outer portion of the eye
What is the role of the cornea?
It filters light first
Describe the sclera
It is a continuation of the cornea
What part of the eye does the sclera form?
It is responsible for the white part of your eye
What are the responsibilities of the sclera and cornea?
They both protect the eye
What is the role of the sclera
It is the attachment point of all the muscles to be able to move the eye
Name the structures that form the outer layer fo the eye
The cornea and sclera
What is the middle layer of the eye composed of?
- The choroid
- the iris
- Ciliary body
Describe the choroid
It is very vascular
Why is the choroid very vascular
It supplies both the cornea and the retina
What is the iris and what us it responsible for?
It is a pigmented layer responsible for our eye color and it controls the amount of light entering the eye
What is the Iris composed of?
Different muscles the are in a circular shape
What do the muscles surrounding the iris do?
They can either contract or dilute to change the diameter of the pupil
What is the pupil?
The central opening of the iris
What does the Ciliary body attach via?
Attaches via the suspensory ligament to the lens
What does the Ciliary body do?
By pulling on the suspensory ligaments it can stretch and change the shape of the lens
This ultimately control the amount of light reaching the retina
What is the inner most layer?
The retina
What is the retina full of?
Neurones that receive light
What is found on the visual axis of the retina?
The macula
Describe the macula
It Is an area where there is a high density of cones only
What is the centre of the macula called?
The fovea
What is special about the fovea?
It is the area where we have the highest visual acuity
Name cranial nerve 2
The optic nerve
Where does the optic nerve exit the retina from?
The optic disk
What is social about the otic disk
There are no photoreceptors in that area (the human blindspot)
What is the cornea a major area of?
Refraction
What is the retina an extension of?
The diencephalon
What can the retina be split into?
a non-neuronal and a neuronal layer.
What does the non-neuronal layer consist of?
PIgmented epithelium
Where is the non-neuronal layer found?
It Sits against the choroid and is light absorbing.
What does the pigmented epithelium of the retina do?
It absorbs light first
What does the neural layer consist of?
Photoreceptors, bipolar cells, ganglion cells
What do the cells of the pigmented epithelium connect to ?
the first Neurones:
The photoreceptor part of the neural layer
What are the 2 types of photoreceptors called?
Rods
Cones
What do the photoreceptors cells connect to ?
Bipolar cells
What do the bipolar cells connect to ?
Ganglion cells
What do the axons of the ganglion cells exit as?
The optic nerve