Vision

Question 0

Cornea

Answer 0

Transparent region of sclera

Question 1

Sclera?

Answer 1

Outer fibrous layer

Connected to extra ocular muscles

Question 2

Iris

Answer 2

Pigmented region

Question 3

Pupil

Answer 3

Opening in iris
Aperture size determined by muscles of the iris
Innervated by ANS

Question 4

Aqueous humour?

Answer 4

Fluid between cornea and lens

Question 5

Suspensory ligament

Answer 5

Attaches lens to ciliary body

Question 6

Capillary body

Answer 6

Smooth muscle

Contraction alters shape of eye

Question 7

Vitreous humour

Answer 7

Fluid behind lens

Question 8

Retina

Answer 8

Contains photoreceptors

Question 9

Optic disc

Answer 9

Axons of retinal neurons enter the optic nerve

Question 10

Fovea

Answer 10

Concentration of cones

Question 11

Choroid

Answer 11

Vascularised layer

Question 12

How is the position of the eye controlled?

Answer 12

6 extra ocular muscles innervated by 3rd,4th and 6th cranial nerves
Stimuli include visual and vestibular info

Question 13

Types of eye movement?

Answer 13

SACCADES- jerky, rapid eye movements which centre images on the fovea
PURSUIT MOVEMENTS- slow movement of the eye, tracking an object
VERGENCE MOVEMENTS- mirror image movements of the eye, so images remain in focus on both retinas

Question 14

Describe the visual pathways

Answer 14

Axons of ganglion cell gather at the optic disc and pass into the optic nerve
2 optic nerves converge to form the optic chiasm at the base of the brain
Axons from the nasal retina decussate, those for temporal retina remain ipsilateral
Optic tracts this formed terminate in LGN
some collateral fibres from the optic tract terminate in the brainstem
Fibres from LGN terminate in primary visual cortex

Question 15

3 phases of CP

Answer 15

Preceitical- visual circuitry preformed without visual experience
Critical- modification of existing circuitry
Post critical- similar experience to above, has no effect (?)

Question 16

What are NDMA receptors ?

Answer 16

Subset of ionotropic glutamate receptors
Mediate a slower epsp and produce a greater Ca permeability
Readily blocked by Mg2+ overcome by sustained depolarisation

Question 17

What is LTP?

Answer 17

Long term potentation
Long lasting enhancement of synaptic transmission occurring at CNS synapses
Opposite is ltd

Question 18

What is inhibitory activity?

Answer 18

In the cortex

Important in determining developmental processes

Question 19

What do neurotrophins do?

Answer 19

Regulate neuronal survival and differentiation

NGF BDNF NT-3

Question 20

What role do neurotrophins play in the critical period?

Answer 20

Control duration

Block endogenous BDNF,

Question 21

Mechanism of actions of neurotrophins

Answer 21

Production and release dependent on visual activity
Modulate both pre and post synaptic function- fast, altering transmitter release
Slow- modulation of gene expression
Production and electrical activity are linked might be a means by which connections are strengthened
Each NT has a specific target

Question 22

What other factors affect visual plasticity?

Answer 22

Factors in extra cellular environment
tPA- extracellular protease induced by electrical activity
Glycoproteins in extracellular compartments of CNS may influence plasticity