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Ophthalmology > Physiology > Flashcards

Physiology Flashcards

1
Q

What is CSF?

A

A clear colourless liquid composed mostly of water

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2
Q

What are the 3 major functions of CSF?

A

mechanical protection homeostatic function circulation

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3
Q

How does CSF contribute to mechanical protection?

A

It is a shock absorbing medium that protects brain tissue (brain floats inside the cranial cavity)

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4
Q

How does CSF have a homeostatic function?

A

PH of CSF affects pulmonary ventilation and cerebral blood flow. It also transports hormones

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5
Q

How does CSF help with circulation?

A

it is a medium for minor exchange of nutrients and waste products between blood and brain tissue

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6
Q

How can CSF for clinical analysis be obtained?

A

lumbar puncture

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7
Q

Does CSF contain lots or a little bit of protein?

A

very little protein

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8
Q

At 3 weeks of embryological development what does the developing nervous system consists of? What does this structure give rise to in adults?

A

neural canal- that adult’s brain ventricles and the spinal cords central canal

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9
Q

what does the chord plexus develop from?

A

cells in the walls of the ventricles

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10
Q

in the adult brain where are choroid plexuses found?

A

in the 3rd, 4th and lateral ventricles

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11
Q

How are the lateral ventricles connected to the the third ventricle?

A

intraventricular foramena

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12
Q

how are the 3rd and 4th ventricles connected?

A

cerebral aquaduct

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13
Q

how is the 4th ventricle connected to the subarachnoid space?

A

median aperture and lateral apertures

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14
Q

What does the blood brain barrier consist of?

A

capillary endothelium, its basal membrane and perivascular astrocytes

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15
Q

what do tight junctions between brain endothelial cells prevent?

A

paracellular movement of molecules

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16
Q

which parts of the brain do not have a blood brain barrier?

A

circumventricular organs or pineal glands

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17
Q

what is the function of the blood brain barrier?

A

protects brain from common bacterial infections and toxins

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18
Q

what is hydrocephalus?

A

accumulation of CSF in the ventricular system or around the brain

19
Q

What is papilloedema?

A

optic disc swelling due to raised ICP

20
Q

what are the visual symptoms of papilloedema?

A

enlarged blind spot blurring of vision visual obscuration loss of vision

21
Q

what is aqueous humour?

A

a specialised fluid that bathes the structures of the eye

22
Q

what does aqueous humour provide?

A

oxygen and metabolites

23
Q

what cells are responsible for th production of aqueous humour?

A

the epithelial layer of the ciliary body

24
Q

Outline the cellular structure of the retina (from anterior to posterior)

A
  • photoreceptor - receive signal
  • [horizontal cells (input from photoreceptors project to other photoreceptors and bipolar cells)] - lateral connection
  • bipolar cells
  • amacrine cells (input from thebipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells)] -lateral connection
  • ganglion cells
25
Q

What do the photoreceptors do?

A

convert electromagnetic radiation to neural signals - tranduction

26
Q

what are the 2 types of photoreceptor?

A

rods and cones

27
Q

What are the 4 main regions of photoreceptors?

A

outer segment

inner segment

cell body

synaptic terminal

28
Q

what is the resting membrane potential of photoreceptors?

A
  • 20 mV
29
Q

upon light exposure what happens to the membrane potential of photoreceptors?

A

it hyperpolarises

30
Q

what is the name of the current that causes the membrane potential of photoreceptors to change?

A

the dark current

31
Q

what is the signal that enables the brain to percieve objects in the visual field?

A

The change in Na+ with light

32
Q

what are the visual pigment molecules called and where are they found?

A

Rhodospin present in the membrane folds in the outer segment of photoreceptor cells

33
Q

What effect does light have on the sodium channels in the photoreceptor membrane - briefly outline how this happens.

A

causes the Na+ channels to close

light causes change in the structure of the retinal in Rhodopsin

This actiavates a molecular cascade –> reduced cGMP

closure of cGMP Na+ channels

reduced Na+ entry results in hyperpolarisation

34
Q

What is the basis of phototransduction?

A

modulation of the dark current

35
Q

Fill in the blanks

dark- current channels are in the dark and in response to light

They are gated channels that are permeable to

The resting membrane potential is . This is more than most neurons and so results in the steady release of neurotransmitter.

A

dark- current channels are open** in the dark and **closed in response to light

They are cGMP gated channels that are permeable to Na+

The resting membrane potential is -20mV. This is more positive than most neurons and so results in the steady release of neurotransmitter.

36
Q

what helps to distinguish between two nearby points?

A

photoreceptor spacing and refracrive power

37
Q

What is visual acuity

A

the clarity of vision - distinguishing two nearby objects

38
Q

in what type of light do rods help us to see in?

In what type of light do cones help s to see in?

breifly explain why

A

Rods- dim light

cones - normal daylight

more convergence in rod syste, increasing sensitivity while decreasing acuity

39
Q

how many photoreceptor types are there in the human retina and what are they?

A

4 types:

  1. short wave cone - blue light
  2. middle wave cone - green light
  3. long wave cone - red light
  4. rods - black and white
40
Q

where are rods and cones distributed over the retina?

rods - peripheral retina

cones - central retina (fovea)

A
41
Q

fill in the blanks:

Each eye sees part of the visual space -

but their visual fields to create a

A

Each eye sees part of the visual space - monocular visial field

but their visual fields overlap** to create a **binocular visual field

42
Q

How is the retina divided and where is it divided?

A

into a nasal and hemiretina relative to the fovea

43
Q

fill in the blanks

nerve fibres from the the half of each retina cross over at the

A

nerve fibres from the the nasal half of each retina cross over at the optic chiasm

Ophthalmology (9 decks)

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