The pupil response 1 Flashcards Preview

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Flashcards in The pupil response 1 Deck (43):
1

What happens in low light level?

Mydriasis - dilation of the pupil in low light level

2

What is average dilation of pupil?

8mm

3

What happens in bright light level?

Miosis - constriction of the pupil in bright light level

4

What is average constricted pupil size?

2mm

5

How are pupils size determined?

light levels
genetics
age

6

What happens to pupils as we get older?

Constricted pupil so harder at night to read

7

what do you call large and small pupil sizes/

macrocoria -big
microcoria - small

8

What does genetic factors influence?

Resting pupil size

9

What is the resting pupil size of males>/

9mm

10

What is the resting pupil size in females?

3mm

11

What is the resting pupil size in children?

6mm

12

What was used to dilate pupil?

Atropine

13

Why did womens use atropine?

Make eyes look larger and make them look younger

14

What happens to pupil in very bright light for long time?

in 200ms pupil gets smaller
takes 2 half second to constrict fully
as light levels get lower pupil response takes longer and constricts less

15

What is hippus?

The pupil oscillates around average steady state

16

What is the function of pupil?

To regulate the amount of light entering the eye

17

What is the difference between fully constricted and fully dilated pupil?

x16

18

How much does fully dilated and fully constricted pupil alter the light entering the eye bye?

1.2 log units

19

What does constriction do?

Increases image quality by increasing depth of focus
and reduce amount of spherical aberrations

20

How can you reduce spherical aberrations?

By closing the pupil- make smaller and cut out any peripheral rays

21

How does the traid improve image quality? (3)

Accommodation focuses the object
convergence puts the image on fovea
pupil constriction increases depth of field

22

What does human pupil respond to?

Changes in illuminance
viewing near objects
cortical influences - girls

23

What does the iris contain?

Two smooth muscles - dilator and sphincter muscles

24

What is the orientation of the iris muscles?

sphincter- circular muscles
dilator - runs radially

25

Where is dilator muscle?

>Close to ris pigmented double epithelium (myoepithelium)

26

What is the dilator muscle innervated by ?

Sympathetic branch of autonomic nervous system

27

Where is the sphincter muscle?

separated from iris pigmented epithelium

28

What innervates the sphincter muscle?

Innervated by the parasympathetic branch of the autonomic nervous system

29

How do pupils respond to in animals without rods and cones?

Mice can also respond to light even without photoreceptors because they have melanopsin that contain retinal ganglion cells that respond in the same way

30

What is the initial stage of pupil constriction?

light absorbed by retinal photoreceptors
>rods and cones - lower intensity
>melanopsin containing retinal ganglion cells - high light levels
>ganglion cells leave retina and stimulate ganglion cells in optic nerve

31

What happens to pathway after optic nerve?

To the optic chiasm- decussation- project axons into thE LGN - synapse to optic radiation in visual cortex and results to conscious vision

32

Not all output goes to visual cortex where does it go?

not all vision is conscious
retinal projection to the OPN (bilateral ) and comes from both eyes

33

What is OPN?

Olivary Pretactal nuclei

34

What happens after OPN?

Fibres go directly to the ipsilateral Edingher Westphal nucleus and also to contralateral EWN to mediate consensual response vai the posterior commisure

35

Explain sensory limb of reflex ARC?

>Light absorbed by photoreceptors(rods, cones, melanopsin ganglion cells)
>activity in the ON
partial decussation at the chiasm
>Projection to OPN
Bilateral Projection to EWN

36

what is the motor innervation of the iris muscles?

Autonomic nervous system

37

what is the difference between sympathetic and parasympathetic ganglia?

Sympathetic ganglia are near spinal chord
Parasympathetic ganglia are located by effector

38

What is the sensory pathway of pupil constriction?

>Bilateral projection to OPN olivary pretectal nuclei from the retina
>fibres to EWN of both sides

39

What is the motor pathway of pupil constriction?

Preganglionic parasympathetic fibres travel from the EWN within the 3rd nerve to the ciliary ganglion

Postganglionic fibres innervate the iris sphincter muscle within short ciliary nerves

40

How do ciliary ganglion cells synapse ?

Ach as neurontransmittors

41

What does Ach bind to?

Muscarinic receptors

42

Where do parasympathetic fibres arise from?

Parasympathetic fibres mediating pupillary response arise in the EWN

43

Where do ciliary muscles run?

Ciliary muscles run back to the eye, run to the choroid in front iris and innervate the sphincter pupillae muscle for constriction