Lecture 19

Question 1

What type of light are rods able to pick up?

Answer 1

Black and white

Question 2

What type of light are cons able to pick up?

Answer 2

Colour

Question 3

Where are rods located?

Answer 3

Periphery of the retina

Question 4

Where are the cones located?

Answer 4

Fovea

Question 5

What type of photopigment is located within rods?

Answer 5

Rhodopsin

Question 6

What type of photopigment is located within cones?

Answer 6

3 different types, depend on the photoreceptor ability

Question 7

What is the structure of rods and cones?

Answer 7

Outer segment has photopigment
Inner segment contains nucleus
Synaptic terminal contains neurotransmitter for signalling of nerves

Question 8

What are the three structures of the brain other than the visual cortex to which signals from the eye will project?

Answer 8

Hypothalamus- involved in regulation of circadian rhythms
Prectectum- reflex control of the pupil and the lens
Superior colliculus- orientating movement of the head and eyes

Question 9

Explain the pupillary constrictor pathway:

Answer 9

1. Retina
2. Optic nerve (CN II)
3. Optic chiasm
4. Optic tract
5. Pretectal nucleus
6. Parasympathetic nucleus of oculomotor nerve (CN III)
7. Preganglionic CNII fibres
8. Ciliary ganglion
9. Post-ganglionic parasympathetic axons to inner circular constrictor muscle

Question 10

What is the pathway that is involved in the menace response?

Answer 10

1. Retina
2. Optic nerve
3. Optic chiasm
4. Optic tract
5. Lateral geniculate nucleus
6. Optic radiation
7. Visual cortex
8. Primary motor cortex
9. Pontine nucleus
10. Middle cerebellar peduncle
11. Ipsilateral cerebellar cortex
12. Efferent cerebellar pathway
13. Facial nuclei (CN VII)
14. Facial muscles- obicularis oculi

Question 11

What are the symptoms involved in Horner syndrome?

Answer 11

• Miosis- refers to where the parasympathetic nervous system is more active than the sympathetic and hence dilation of the pupils results
• Enopthalmos- retraction of the eyeball as sympathetic influence over periorbital muscle is lacking
• Prolapse of the third eyelid
• Ptosis is drooping of the third eyelid
• Peripheral vasodilation- as the vasoconstrictor tone increases more blood is flowing to the eyes and nose, they get warmer and the nasal cavities become congested- often leads to sweating in horses