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Ophthalmology > Physiology > Flashcards

Physiology Flashcards

1
Q

What produces the cerebrospinal fluid?

A

secretory epithelium of the choroid plexus

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2
Q

What are the main functions of the cerebrospinal fluid?

A
  • shock-absorbing to protect brain tissue
  • pH of CSF affects pulmonary ventilation and cerebral blood flow
  • exchange of nutrients and waste
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3
Q

How is cerebrospinal fluid obtained for analysis?

A

lumbar puncture

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4
Q

What is meant by the brain’s ventricles?

A

larger areas of the neural canal

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5
Q

How is the choroid plexus formed?

A
  • Developing arteries invaginate the ventricle to form the choroid fissure
  • These then enlarge into villi and form the choroid plexus
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6
Q

Plasma from the blood vessels in the choroid plexus contributes to the CSF. TRUE/FALSE?

A

TRUE
epithelial cells absorb plasma and modify it
then released from opposite

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7
Q

What constituents are found in higher concentrations in CSF than in plasma?

A

CO2
Cl
Na

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8
Q

What constituents are in higher concentrations in plasma than CSF?

A

Protein

Cholesterol

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9
Q

What connects the lateral ventricle to the third ventricle?

A

intraventricular foramina (of Monroe)

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10
Q

What connects the third and fourth ventricles?

A

Cerebral Aqueduct (of Sylvius)

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11
Q

What structures allow the CSF to exit the ventricles and enter the subarachnoid space?

A

Foramen of Magendie

Foramina of Luschka

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12
Q

What creates the blood brain barrier?

A

Tight junctions between brain endothelial cells prevent paracellular movement of molecules

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13
Q

What parts of the brain do NOT contain the blood brain barrier?

A

circumventricular organs or pineal gland

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14
Q

What tumours most commonly arise in the ventricles, choroid plexus and CSF?

A
  • Colloid cyst (found at interventricular foramen)
  • Ependymomas (from ependymal cells lining ventricles)
  • Choroid plexus tumours
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15
Q

An arterial haemorrhage between the skull and dura matter is known as what?

A

Epidural hematoma

Subarachnoid hemorrhage

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16
Q

A subdural hematoma occurs between which layers?

A

venous bleed

between dura matter and arachnoid

17
Q

what is hydrocephalus?

A
  • accumulation of CSF in ventricular system (obstruction or overproduction)
  • enlargement of one or more ventricles and increase in CSF pressure
18
Q

How is papilloedema caused?

A

optic disc swelling due to increased intracranial pressure

transmitted to the subarachnoid space surrounding the optic nerve

19
Q

How does the optic disc appear on the fundus exam if there is papilloedema?

A

optic disc bulges and appears blurred

20
Q

Describe the course of the aqueous humour

A 
ciliary body 
posterior chamber 
flows into the anterior chamber
drains to the scleral venous sinus 
through trabecular meshwork and the canal of Schlemm
21
Q

Describe the 2 layer structure of the ciliary epithelium

A

pigmented epithelium faces the blood

non-pigmented epithelium faces opposite direction

22
Q

Briefly describe how Na and Cl make their way into the aqueous humour

A

Carbonic anhydrase catalyses a reaction to produce H+ and HCO3
H+ is exchanged for Na into the pigmented cell
HCO3 is exchanged for Cl into the pigmented cell
Na and CL then pass to non-pigmented cell via gap junctions
Na and Cl use the Na/K/CL co transporter to leave non-pigmented cell and enter aqueous humour

23
Q

What drugs can be used to halt the production of aqueous humour?

A

Carbonic anhydrase inhibitors

24
Q

Give examples of carbonic anhydrase inhibitors which can be used in glaucoma

A

Dorzolamide - eye drops (=> avoids systemic side effects )

Acetazolomide - oral (beware of kidney acidosis)

25
Q

After light hits the photoreceptors, what cells does the signal pass to?

A

photoreceptor -> bipolar cell -> ganglion cell

26
Q

Where are Action Potentials generated after light is sensed at the photoreceptors?

A

Only at ganglion cell

the rest only depolarise the membrane, but dont generate an AP

27
Q

What are the two shapes of photoreceptors?

A

Rods

Cones

28
Q

What effect does light have on the cell membrane potential?

A

hyperpolarizes

closes cGMP gated Na channel => less positive into cell

29
Q

How do photosensitive rods hyperpolarize the membrane?

A

Cis-retinal + opsin = Trans-retinal
Trans-retinal activates transducin
Transducin activates cGMP phosphodiesterase (PDE)
PDE hydrolyses cGMP and prevents Na influx
=> HYPERPOLARISED

30
Q

What characteristics of photoreceptors can increase visual acuity?

A

spacing of photoreceptors (closer increases acuity)

volume of photoreceptors

31
Q

Rod photoreceptors are usually used for seeing in normal daylight. TRUE/FALSE?

A

FALSE
cone receptors are for seeing in daylights
rod receptors are for seeing in dim light

32
Q

How do photoreceptors allow us to see different shades of the same colour?

A

mixture of long, middle and short wave cones can create different shades

33
Q

What part of the retina contains cones rather than rods?

A

Fovea (centre of macula)

Ophthalmology (13 decks)

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