Week 2: Introduction to the Visual System

Question 1

Describe the conceptual stages how sensory systems convey messages to the brain?

Answer 1

Using the common sequence of events (psychophysics)

1. Energy (external stimulus)
2. Receptor
3. Electrophysiological signal (movement of ions)
4. Brain
5. Perception

Question 2

List the features of the sensory system

Answer 2

• Vestibular cortex
• Somatosensory cortex
• Olfactory cortex
• Gustatory cortex
• Audiotory cortex
• Visual cortex

Question 3

Vestibular cortex

Answer 3

Balance (in the ear)

Question 4

Somatosensory cortex

Answer 4

Touch (pain response)

Question 5

Olfactory cortex

Answer 5

Smell (nose)

Question 6

Gustatory cortex

Answer 6

Taste (tongue)

Question 7

Auditory cortex

Answer 7

Hearing (ears)

Question 8

Visual cortex

Answer 8

Seeing (eyes)

Question 9

Anatomical Plan Pathway

Answer 9

1. Receptor
2. Thalamus (relay station for reorganisation)
3. Cortex

Question 10

Physiological Processing Plan Pathway

Answer 10

1. Reception
2. Transduction
3. Coding
4. Output

Question 11

Describe the basic sensory visual processing pathway

Answer 11

1. Photoreceptors
2. Retinal ganglion cells
3. Optic nerve
4. Thalamus (LGN)
5. Optic radiations
6. Visual cortex

Question 12

What information is important for the visual system to detect and process?

Answer 12

• Colour contrast
• Illumination
• Motion
• Attention

Question 13

Sagittal Plane

Answer 13

• Divides body/object into R and L parts

- Side to side

Question 14

Transverse Plane

Answer 14

• Divides body/object into superior and inferior parts

- Top and bottom

Question 15

Coronal/Frontal Plane

Answer 15

• Divides body/object into front and back parts

- Front to back

Question 16

Anterior/Rostral

Answer 16

Front

Question 17

Posterior/Caudal

Answer 17

Back

Question 18

Superior/Dorsal

Answer 18

Top

Question 19

Inferior/Ventral

Answer 19

Bottom

Question 20

Proximal

Answer 20

Closer to the origin of the structure

Question 21

Distal

Answer 21

Further from the origin of the structure

Question 22

Medial

Answer 22

Towards the midline

Question 23

Lateral

Answer 23

Away from midline

Question 24

Ipsilateral

Answer 24

Same side of body

Question 25

Contralateral

Answer 25

Opposite side of body

Question 26

Name the chambers of the human eye

Answer 26

1. Anterior chamber
2. Posterior chamber
3. Vitreous chamber

Question 27

Anterior chamber: what is it filled with and measurement, depth, anterior and posterior limit

Answer 27

• Filled with aqueous humour (0.2 mL)
• Measures 3 mm at greatest depth centrally
• Anterior limit: cornea & sclera
• Posterior limit: iris & lens

Question 28

Posterior chamber: what is it filled with and measurement, anterior, posterior and peripheral limit

Answer 28

• Filled with aqueous humour (0.06 mL)
• Anterior limit: iris
• Posterior limit: lens & zonules
• Peripheral limit: ciliary processes

Question 29

Vitreous chamber: what is it filled with and measurement, anterior and posterior limit

Answer 29

• Largest chamber and filled with vitreous humour (6.5 mL)
• Anterior limit: lens & zonules
• Posterior limit: retina

Question 30

What are the layers of the human eye?

Answer 30

1. Internal nervous layer (retinal layer)
2. Intermediate vascular pigmented layer (uvea)
3. External, fibrous layer (cornea & sclera)

Question 31

What are the components in the internal nervous layer (retinal layer)

Answer 31

• Photoreceptors = rods for capturing light and 3 cones for capturing light in bright illumination (daylight, colour vision)
• Bipolar cells
• Ganglion cells
• Foveal area = devoid of blood vessels & very tightly packed with photoreceptors (helps with creating sharp images)

Question 32

What are four functions of the internal nervous layer (retina layer)?

Answer 32

• Nourishment
• Waste removal
• Protection
• Sharp imagery & fixation

Question 33

What are the components in the intermediate vascular pigmented layer (uvea) and their functions?

Answer 33

1. Iris
   - To control the amount of light entering the pupil
   - To allow light in, in dim light conditions
2. Ciliary body
   - Production of the aqueous humous and lens zonules
   - Holds lens in place
   - Facilities accomodation
3. Choroid
   - Supplies blood to the retina and pigmented epithelium

Question 34

What are the components in the External fibrous layer. Describe its characteristic and function

Answer 34

1. Sclera
   - Anteriorly forms ‘white’ of the eye
   - Function: protection, fixation & teaming
2. Cornea
   - Characteristic: transparent
   - Function: main refractive power of the eye

Question 35

What are the four sections of the optic nerve and its measurements with their position?

Answer 35

1. Intraocular/optic nerve head: 1 mm long
2. Intraorbital: 25 mm long
   - loosely held bounded by sclera anteriorly & optic canal posteriorly
3. Intracanalicular: 10 mm long
   - begins at optic foramen, ends at insertion to intracranial cavity
4. Intracranial: 15 mm long
   - extending from intracranial cavity to optic chiasm

Question 36

What are the functions for optic nerve?

Answer 36

• Anterior extension of white matter of the brain

- Carries axons of ganglion cells of the retina to the lateral geniculate (LG) body then to the visual cortex