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opthalmology > physiology > Flashcards

physiology Flashcards

1
Q

what is cerebrospinal fluid produced by

A

the secretory epithelium of the choroid plexus of each lateral ventricle

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2
Q

where does CSF circulate

A

in the subarachnoid space

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3
Q

where is CSF absorbed

A

into venous circulation

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4
Q

3 functions of CSF

A
  • mechanical protection - shock absorbing medium that protects brain tissue
  • homeostatic function - pH affects pulmonary ventilation and cerebral blood flow, transports hormones
  • circulation - medium for minor exchange of nutrients and wast products between blood and brain tissue
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5
Q

what is normal CSF like

A

contains little protein and little immunoglobulins

-clear and colourless

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6
Q

what is the choroid plexus

A

networks of capillaries in walls of ventricles

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7
Q

what ions does CSF secretion involve the transport of from basolateral to apical

A

Na+
Cl-
HCO3-

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8
Q

what are the ventricles of the brain

A

a communicating network of cavities filled with cerebrospinal fluid (CSF) and located within the brain parenchyma

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9
Q

what are the four ventricles connected by

A
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10
Q

CSF circulation

A
  • formed in lateral ventricles
  • flows to third ventricle through interventricular foramina
  • more CSF added by choroid plexus in roof of third ventricle
  • flows through aqueduct of midbrain
  • into fourth ventricle
  • another choroid plexus in fourth adds more CSF
  • then enters subarachnoid space
  • then circulates in central canal of spinal cord
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11
Q

how does CSF return to venous blood

A

through arachnoid granulations into superior sagittal sinus

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12
Q

what is blood supply ot the brain restricted by

A

the blood-brain barrier

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13
Q

what is hydrocephalus

A

accumulation of CSF in the ventricular system of around the brain

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14
Q

what is papilloedema

A

optic disc swelling due to increased intracranial pressure transmitted to the subarachnoid space surrounding the optic nerve

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15
Q

visual symptoms of papilloedema

A
  • enlarged blind spot
  • blurring of vision
  • visual obscurations
  • loss of vision
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16
Q

what is the aqueous humour

A

a specialized fluid that bathes the structures within the eye
-provides oxygen and metabolites and contains bicarbonate

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17
Q

what does bicarbonate do

A

buffers the H+ produced in the cornea and lens by anaerobic glycolysis

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18
Q

where is aqueous humour produced

A

epithelial layer of ciliary body

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19
Q

what are the two layers of ciliary epithelium

A

pigmented and non-pigmented

20
Q

what is the net movement of Cl- and Na+ through cells from interstitial fluid to aqueous humour accompanied by

A

water moving through ciliary epithelial cells water channels, aquaporins and through paracellular pathway down the osmotic gradient created by solute movement

21
Q

which enzyme is responsible for the production of these ions

A

carbonic anhydrase

22
Q

what must happen to see an object

A
  • the pattern of the object must fall on the vision receptors (accommodation)
  • the amount of light entering the eye must be regulated
  • the energy from the waves of photons must be transduced into electrical signals
  • the brain must receive and interpret the signals
23
Q

where is superior visual field seen

A

lower cortex

24
Q

where is right visual field seen

A

lower cortex

25
Q

what is involved in the visual field

A
  • retina
  • LGN
  • superior colliculus
  • cortex
26
Q

cells outside which layer of the cortex receive input from both eyes

A

4C

2,3,5,6

27
Q

what is amblyopia

A

aka coritcal blindness
term that refers to a variety of visual disorders when there is no problem with the eye but one eye has better vision that the other

28
Q

what does lack of activity cause in the LGN axons

A

less branching

29
Q

what is Hebb’s postulate

A

when an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it

30
Q

what does correlated activity between presynaptic and postsynaptic cells do

A

strengthens synaptic connections between them

cells that fire together, wire together

31
Q

direction of signal transmission in the retina

A

photoreceptors > bipolar cells > ganglion cells

32
Q

what do horizontal cells do

A

receive input from photoreceptors and project to other photoreceptors and bipolar cells

33
Q

what do amacrine cells do

A

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

34
Q

what do photoreceptors do

A

convert electromagnetic radiation to neural signals (trasnduction)

35
Q

name types of photoreceptors

A

rods and cones

36
Q

what causes closure of cGMP-gated Na+ channel

A

all-trans-retinal activates transducin > molecular cascade > decreases cGMP

37
Q

what does lowered Na entry result in

A

hyperpolarization

38
Q

what is the molecular mechanism of phototransduction

A
  • light stimulation of rhodopsin leads to activation of a G-protein, transducin
  • activated G-protein activates cGMP phosphodiesterase (PDE)
  • PDE hydrolyses cGMP reducing its concentration
  • this leads to closure of Na+ channels
39
Q

features of the Dark-current channel

A
  • open in dark
  • closes in light
  • opened by cGMP
  • permeable to Na+
  • keeps photoreceptor Vm more positive than most neurons
  • steady release of neurotransmitter
40
Q

is there more or less glutamate in the dark

A

more

41
Q

what is visual acuity

A

ability to distinguish two nearby poitns

42
Q

what is visual acuity determined by

A

photoreceptor spacing and refractive power

43
Q

what are rods used for seeing in

A

dim light

44
Q

what are cones used for seeing in

A

normal daylight

45
Q

the rod system has a high convergence, what does this mean?

A

increases sensitivity which decreasing acuity

46
Q

do cones have low or high convergence

A

low

47
Q

differences between rods and cones

A

opthalmology (16 decks)

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