NERVOUS SYSTEM Session 6

Question 1

What are the three layers of the eye ?

Answer 1

• Sclera , Choroid , and retina

Question 2

Describe the sclera

Answer 2

• Outer layer, white and fibrous except for the cornea , which is clear.

Question 3

Describe the choroid

Answer 3

• Middle layer , its dark pigment absorbs light that photoreceptors have not absorbed

Question 4

What are some things that the choroid does ?

Answer 4

• It becomes the iris and regulates the size of the pupil
• It also thickens and forms the circular cillary body which controls the shape of the lens for focusing

Question 5

How is the lens attached to the cillary body ?

Answer 5

• it is attached by the suspensory ligaments and divides the eye into two compartments
• The anterior compartment in front of the lens and the posterior compartment behind it

Question 6

What is the anterior compartment of the lens filled with ?

Answer 6

• A clear watery fluid called the aqueous humor

Question 7

What is Glaucoma ?

Answer 7

• Its when drainage ducts are blocked and aqueous hummer builds up , it can cause :
• The resulting pressure compresses the arteries that serve the retina , where photoreceptors are located
• Gradual loss of vision , leading to eventual total blindness

Question 8

Describe the retina

Answer 8

• The third layer , located in the posterior compartment

Question 9

What does the posterior compartment contain that helps to hold the retina in place?

Answer 9

• Vitreous Humor

Question 10

What photoreceptors does the retina contain and do they detect color ?

Answer 10

• Rods : very sensitive to light and does not detect color
• Cones : require bright light and does detect color

Question 11

What are Optic Nerves made of and what do they do ?

Answer 11

• Made of sensory fibers from the retina
• They take nerve signals to the visual cortex in the occipital lobe

Question 12

• review slide 10

Question 13

What does the Fovea Centralls do and where are they located ?

Answer 13

• They are packed with cone cells and are located at the centre of the Macula Lutea
• they make acute vision possible

Question 14

The image on the retina is __________ and _________ from ______ to _______

Answer 14

The image on the retina is INVERTED and REVERSED from LEFT to RIGHT

Question 15

What type of lens is required to view a distant and a near object and what state would do the ciliary muscle be required to be in

Answer 15

• To view a distant object , the ciliary muscle is relaxed and the lens is flat
• To view a near object , the ciliary muscle contracts and a the lens becomes round and thick

Question 16

Describe the structure of the layers within the retina

Answer 16

• The layer closest to the choroid contains the rod cells and cone
• a layer of bipolar cells covers the rods and cones
• then the innermost layer contains the ganglion cells whose fiber form the optic nerve

Question 17

Where are pigment molecules located in rods and cones ?

Answer 17

• In the membrane of the numerous disks located in the outer segment

Question 18

Where are synaptic vesicles located tin rods and cones ?

Answer 18

• at the synaptic endings of the inner segment

Question 19

What is released in the absence of light ?

Answer 19

• Glutamate ( neurotransmitter )

Question 20

What are rhodopsin ?

Answer 20

• It is the visual pigment in rods

Question 21

• What happens when rods absorb light ?

Answer 21

• The rhodopsin splits into opsin and retinal ( derivative of Vitamin A ) then it leads to a cascade of reaction that hyper polarizes the rod and overall inhibits the release of glutamate

Question 22

How does light effect the release of glutamate and at the ON and OFF of the bipolar cells ?

Answer 22

• When the light is on , not inhibits the glutamates and bipolar cells are ON
• When th lights are off , it stimulates glutamate more and the bipolar cells are OFF

Question 23

What is a Blindspot in the eye?

Answer 23

• It is where the optic nerve exits the eye , there are no rods and cones here .

Question 24

How are signals transmitted from the retina to the visual cortex ?

Answer 24

• First nerve impulses are carried by the optic nerves from the eyes to the optic chiasma, then optic nerves continue as optic tracts and signals go to the visual cortex in the occipital lobe

Question 25

How does color blindness occur ?

Answer 25

• When one type of cone is defective or is deficient in number
• The most common one is the inability of cones to detect red and green

Question 26

What is Astigmatism ?

Answer 26

• it is when the cornea or lens Is uneven creating a fuzzy image
• it can be corrected by an uneven lens