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Opthalmology > Physiology > Flashcards

Physiology Flashcards

1
Q

Where is CSF produced

A

The secretory epithelium of the choroid plexus

This is found in the ventricles of the brain (spaces)

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2
Q

Describe the appearance of the CSF

A

Clear, colourless liquid

Mostly water

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3
Q

Roughly how much CSF is produced daily

A

150ml is present at any time and is replaced 3-4x per day

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4
Q

What does CSF give to tissues

A

Water
Amino acids
Ions
Removes metabolites

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5
Q

Describe how CSF ‘circulates’

A

Produced from lateral ventricles
Passes through interventricular foramen to 3rd and then through the cerebral aqueduct to 4th ventricle
They add to CSF as it drains through
Passes through the median and lateral apertures to subarachnoid space
Then absorbed back into venous circulation by passing through arachnoid villi into the SSS

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6
Q

What are the main functions of CSF

A

Mechanical protection - shock absorber that protects brain
Homeostasis - pH affects pulmonary system and cerebral blood flow
Some hormones are transported in it
Provides nutrients

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7
Q

How do you analyse CSF clinically

A

Lumbar puncture
Should be completely clear
Presence of blood or pus indicates a problem

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8
Q

What is the choroid plexus

A

Network of capillaries are lined by the ependymal cells of the ventricles
Good connection between blood and brain

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9
Q

The apical surface if the ependymal cells faces the circulation - true or false

A

FALSE
basolateral surface faces capillary
CSF is secreted through the apical membrane

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10
Q

Which ions are transported in the production of CSF

A

Na, Cl and HCO3

Water also moves across due to ion movement

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11
Q

What drives the ion movement needed for CSF production

A

The distribution of ion channels

NOT arterial blood pressure

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12
Q

Are the ventricles in the brain connected to each other?

A

YES

There are 4 - 2x lateral and the third + fourth

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13
Q

How many ventricles are in the brain

A

4
2x lateral
The third
The fourth

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14
Q

How does CSF pass from the ventricles to the subarachnoid space

A

There are 3 holes in the roof of the 4th ventricles
The median aperture
2x lateral apertures

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15
Q

How does CSF return to the venous system

A

Passes into the superior sagittal sinus via

Gets there by entering arachnoid villi - areas of arachnoid layer that push up into dura to be nearer blood

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16
Q

What forms the blood brain barrier

A

Tight junctions between endothelial cells in the brain capillaries- prevent molecules passing through

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17
Q

What are the pros and cons of the BBB

A

Pro = protects brain from many bacterial infections and toxins
Con - barrier to drug delivery into the CNS

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18
Q

What is the aqueous humour

A

Specialized fluid that bathes the structures within the eye.
It provides oxygen and metabolites and contains bicarbonate

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19
Q

Where is aqueous humour produced

A

Epithelial layer of the ciliary body

20
Q

Describe the path of aqueous humour

A

Produced in ciliary body
Flows into anterior chamber
Drains into the scleral venous sinus
Continuous process of secretion and reabsorption

21
Q

How do you block the production of aqueous humour

A

Block carbonic anhydrase (involved in its production)

Can be used to reduce pressure in glaucoma

22
Q

Which ions are involves in the production of aqueous humour

A

carbonic anhydrase in the cells generates HCO3

The bicarb is used to drive Na and Cl movement in the cell

23
Q

What 4 things must happen for us to see an object

A

Pattern of object must fall on the visual receptors in the retina
Amount of light entering must be regulated
The energy from light must be transduced to electrical signals
The brain must receive these signals

24
Q

Describe the layers of the retina

A

Photoreceptors are the furthest back
Bipolar cells sit in front and Ganglion cells in front of those

Light passes to back of eye and signal passes forward again

25
Q

What are the 2 types of photoreceptors

A

Rods and cones

3 different types of cones

26
Q

What is the function of photoreceptors

A

Converts electromagnetic radiation to neural signals

27
Q

Describe the changes in membrane potential in photoreceptors

A

When exposed to light the photoreceptor becomes hyperpolarised
Doesn’t quite trigger a AP
Releases less glutamate

28
Q

How is an AP triggered in the eye

A

Hyperpolarisation of photoreceptor then bipolar cells causes AP generation in ganglion cells
Caused by light

29
Q

What is the dark current in the eye

A

A cGMP-gated Na+ channel that is open in the dark and closes in the light
More glutamate is released in the dark so more sodium moves in

30
Q

What is rhodopsin

A

A visual pigment molecule
Made of retinal and opsin
Undergoes a conformational change when exposed to light
When active it triggers a cascade involving G proteins which closes the Na channel
Causes AP

31
Q

What is visual acuity and what determines it

A

Ability to distinguish two nearby points. Determined largely by photoreceptor spacing and refractive power

32
Q

What cells allow us to see colour

A

Cones cells

Different types absorb different wavelengths of light

33
Q

List features of cone cells

A 
See colour 
Found in central retina - fovea 
Low convergence 
Low light sensitivity - work in well lit 
High visual acuity
34
Q

List features of rod cells

A 
Achromatic - no colour vision 
Peripheral retina 
High convergence 
High light sensitivity - used in dark places 
Low visual acuity
35
Q

Why is the left visual field perceived by the right side of the brain

A

The nerves cross over at the optic chiasm

36
Q

Where is visual information processed

A

Visual cortex in the brain

37
Q

What are the meninges

A

3 layers of tissue surrounding the entire brain
Dura mater - tough, fibrous layer
Arachnoid mater - thinner, spidery layer
Pia mater - single cell layer

38
Q

CSF is found between which layer of the meninges

A

Deep to the arachnoid layer (subarachnoid space)

Between arachnoid and pia

39
Q

What passes through the tentorial notch in the dura mater

A

The brain stem and some cranial nerves

40
Q

The optic nerves are covered by meninges - true or false

A

TRUE

therefore some consider optic nerves as extensions of the brain/CNS

41
Q

Which type of fibres are contained in the oculomotor nerves

A

Motor

Parasympathetic

42
Q

Describe the trochlear nerve

A

Long intracranial course

Very thin as only supplies 1 muscle - superior oblique

43
Q

Describe the abducent nerve

A

Also has a long intracranial course

Innervates the lateral rectus in eye

44
Q

What do the parasympathetic fibres of the oculomotor nerve supply

A

Constrictor papillae
Responsible for constricting the pupil
If damaged the eye will dilate

45
Q

What are the 3 components of the accommodation reflex

A

Fattening of the lens
Constriction of the pupil
Convergence of the eyes

46
Q

What is the purpose of the accommodation reflex

A

It is used to focus on near objects

Opthalmology (9 decks)

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