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Opthalmology > CsfVision again > Flashcards

CsfVision again Flashcards

1
Q

Normal CSF

A

Normal CSF is clear and colorless, contains little protein (15-45mg/dl), little immunoglobulins and only 1-5 cells/ml

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2
Q

Who would you see idiopathic intracranial hypertension/pseudotumour cerebri in?

A

Obese females of child bearing age

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3
Q

Management of idiopathic intracranial hypertension/pseudotumour cerebri

A

Weight loss, medication and potentially ventriculopertioneal shunt

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4
Q

Normal pressure hydrocephalus triad

A

Dementia
Incontinence
Gait disturbances

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5
Q

What does aqueous humour contain?

A

Oxygen, metabolites, bicarbonate

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6
Q

Ascorbate

A

Powerful antioxidant

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7
Q

Purpose of bicarbonate

A

Buffers the H+ produced in the cornea and lens by anaerobic gylcolysis

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8
Q

Direct (vertical) pathway for signal transmission

PBG

A

Photoreceptors
Bipolar cells
Ganglion cells

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9
Q

What do horizontal cells do?

A

Receive input rom photoreceptors and project to other photo receptors and bipolar cells

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10
Q

What do amacrine cells do?

A

Receive input from bipolar cells and project to ganglion cells, bipolar cells and other amacrine cells

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11
Q

What do photoreceptors do?

A

Convert electromagnetic radiation into neural signals (transduction)

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12
Q

4 main segments of photoreceptors?

A

Outer segment
Inner segment
Cell body
Synaptic terminal

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13
Q

Which current allows the brain to perceive objects in the visual field in light?

A

Na+ dark current

-cGMP channel open in the dark and closes in the light

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14
Q

Vm of photoreceptors

A

-20

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15
Q

Vm of photoreceptors

A

-20

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16
Q

Ciliary epithelium

A

Pigmented epithelium overlain by inner non pigmented epithelium

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17
Q

How is dorzolamide administered?

A

Eye drops

18
Q

How is acetozolamide administered?

A

Oral administration –> targets kidneys

19
Q

Most common type of glaucoma

A

Primary open angle

20
Q

Pathogenesis of primary open angle glaucoma

A

Raised intra-ocular pressure

Obstruction to aqueous outflow across trabecular meshwork

21
Q

Modulation of the dark channel

A

In the dark,
PNa –> PK (Na channels in the outer segment)
Vm therefore between ENa and EK

In response to light,
PNa is reduced (outer segment channels close), PK > PNa
therefore, Vm –> EK, hyperpolarizes
Change is local and graded

22
Q

Rhodopsin

A

Primary pigment in rod receptors

Sensitive to light and allow light in low conditions

23
Q

Molecular mechanism of phototransduction

A

all-trans-Retinal activates transducin
molecular cascade

decreases cGMP

This leads to closure of cGMP-gated Na+ channel
Lowered Na entry results in hyperpolarization

24
Q

Dark channel and cGMP

A

Opened by cGMP

25
Q

What is the purpose of the dark channel?

A

Keeps photoreceptors Vm more positive than most neurons

26
Q

What does the dark channel transmit?

A

Steady release of neurotransmitter

27
Q

What is visual acuity and how is it determined?

A

Visual acuity is the ability to distinguish two nearby points
Determined largely b photoreceptor spacing

(i.e. lots of photoreceptors together = better visual acuity)

28
Q

Help you to see in dim light

A

Rods

29
Q

Help you to see in normal daylight

A

Cones

30
Q

More convergence in rods or cones?

A

More convergence in rod system, increasing sensitivity while decreasing acuity

31
Q

Short wave cones

A

Blue

32
Q

Middle wave cone

A

Green

33
Q

Long wave cone

A

Red

34
Q 
Chromatic
Central retina (fovea)
Low convergence
Low light sensitivity
High visual acuity
A

Cones

35
Q 
Achromatic
Peripheral retina
High convergence
High light sensitivty
Low visual acuity
A

Rods

36
Q

What is the receptive field

A

The part of the retina that needs to be stimulated to elicit actin potentials from a ganglion cell

37
Q

What is the importance of the central surround organisation?

A

Emphasizes areas of contrast

38
Q

Our visual system detects what differences in light?

A

LOCAL differences in light intesnsity not absolute differences in amount of light

39
Q

Right visual field

A

Left cortex

40
Q

Superior visual field

A

Lower cortex

Opthalmology (10 decks)

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