CsfVision again

Question 1

Normal CSF

Answer 1

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

Question 2

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

Answer 2

Obese females of child bearing age

Question 3

Management of idiopathic intracranial hypertension/pseudotumour cerebri

Answer 3

Weight loss, medication and potentially ventriculopertioneal shunt

Question 4

Normal pressure hydrocephalus triad

Answer 4

Dementia
Incontinence
Gait disturbances

Question 5

What does aqueous humour contain?

Answer 5

Oxygen, metabolites, bicarbonate

Question 6

Ascorbate

Answer 6

Powerful antioxidant

Question 7

Purpose of bicarbonate

Answer 7

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

Question 8

Direct (vertical) pathway for signal transmission

PBG

Answer 8

Photoreceptors
Bipolar cells
Ganglion cells

Question 9

What do horizontal cells do?

Answer 9

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

Question 10

What do amacrine cells do?

Answer 10

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

Question 11

What do photoreceptors do?

Answer 11

Convert electromagnetic radiation into neural signals (transduction)

Question 12

4 main segments of photoreceptors?

Answer 12

Outer segment
Inner segment
Cell body
Synaptic terminal

Question 13

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

Answer 13

Na+ dark current

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

Question 14

Vm of photoreceptors

Answer 14

-20

Question 15

Vm of photoreceptors

Answer 15

-20

Question 16

Ciliary epithelium

Answer 16

Pigmented epithelium overlain by inner non pigmented epithelium

Question 17

How is dorzolamide administered?

Answer 17

Eye drops

Question 18

How is acetozolamide administered?

Answer 18

Oral administration –> targets kidneys

Question 19

Most common type of glaucoma

Answer 19

Primary open angle

Question 20

Pathogenesis of primary open angle glaucoma

Answer 20

Raised intra-ocular pressure

Obstruction to aqueous outflow across trabecular meshwork

Question 21

Modulation of the dark channel

Answer 21

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

Question 22

Rhodopsin

Answer 22

Primary pigment in rod receptors

Sensitive to light and allow light in low conditions

Question 23

Molecular mechanism of phototransduction

Answer 23

all-trans-Retinal activates transducin
molecular cascade

decreases cGMP

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

Question 24

Dark channel and cGMP

Answer 24

Opened by cGMP

Question 25

What is the purpose of the dark channel?

Answer 25

Keeps photoreceptors Vm more positive than most neurons

Question 26

What does the dark channel transmit?

Answer 26

Steady release of neurotransmitter

Question 27

What is visual acuity and how is it determined?

Answer 27

Visual acuity is the ability to distinguish two nearby points Determined largely b photoreceptor spacing (i.e. lots of photoreceptors together = better visual acuity)

Question 28

Help you to see in dim light

Answer 28

Rods

Question 29

Help you to see in normal daylight

Answer 29

Cones

Question 30

More convergence in rods or cones?

Answer 30

More convergence in rod system, increasing sensitivity while decreasing acuity

Question 31

Short wave cones

Answer 31

Blue

Question 32

Middle wave cone

Answer 32

Green

Question 33

Long wave cone

Answer 33

Red

Question 34

``` Chromatic Central retina (fovea) Low convergence Low light sensitivity High visual acuity ```

Answer 34

Cones

Question 35

``` Achromatic Peripheral retina High convergence High light sensitivty Low visual acuity ```

Answer 35

Rods

Question 36

What is the receptive field

Answer 36

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

Question 37

What is the importance of the central surround organisation?

Answer 37

Emphasizes areas of contrast

Question 38

Our visual system detects what differences in light?

Answer 38

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

Question 39

Right visual field

Answer 39

Left cortex

Question 40

Superior visual field

Answer 40

Lower cortex