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ophthalmology > physiology > Flashcards

physiology Flashcards

1
Q

describe CSF

A

clear, colourless liquid comprised mainly of water

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2
Q

what produces CSF

A

secretory epithelium of the choroid plexus located in the ventricles

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3
Q

what are the 3 main function of CSF

A
  1. Mechanical protection = acts as a shock-absorber
  2. Homeostatic functions = pH affects pulmonary ventilation and cerebral blood flow. Also transports hormones
  3. Circulation = medium for minor exchange of nutrients and waste between blood and brain
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4
Q

give a brief description of the circulation of CSF

A

circulates in the subarachnoid space before being absorbed into the venous circulation

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5
Q

what does the choroid plexus develop from

A

cells in the walls o the ventricles

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6
Q

where is the choroid plexus located

A

3rd, 4th, and lateral ventricles

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7
Q

what are choroid cells

A

specialised cells that produce CSF in an active process.

network of capillaries in the walls of ventricles

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8
Q

why can secretion of CSF occur

A

due to the polarised distribution of Na+, Cl-, and HCO3- in the apical or basement membrane of the epithelium cells

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9
Q

describe the circulation of CSF in detail

A

from the choroid plexuses of each lateral ventricle it then flows to the 3rd ventricle via the interventricular foramina. More CSF is added by the choroid plexus in the roof of the 3rd ventricles which then flows through the aqueduct of the midbrain into the 4th ventricle. Another choroid plexus on the 4th ventricle adds more CSF. The CSF then enters the subarachnoid space through 3 openings in the roof of the 4th ventricle before circulating in the central canal of the spinal cord

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10
Q

what is a ventricular haemorrhage

A

accumulation of blood in the ventricles

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11
Q

what is hydrocephalus

A

accumulation of CSF in the ventricle system or around the brain

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12
Q

what is papilloadema

A

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

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13
Q

what is aqueous humor

A

specialised fluid that bathes the structures within he eye

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14
Q

what is the role of aqueous humour

A

provides O2 and metabolites while contains bicarb to buffer the H+ produced in the cornea and lens by anaerobic glycolysis

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15
Q

how and where is aqueous humour produced

A

produced by an energy decent process in the epithelial layer of the ciliary body

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16
Q

describe the circulation of aqueous humour

A

from the ciliary body it flows into the posterior then anterior chamber of the eye before draining to the scleral venous sinus via a trabecular meshwork and canal of schlemm

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17
Q

where is the canal of schlemm located

A

in the angle between the iris and cornea (iridocorneal angle)

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18
Q

how is HCO3- and H+ formed by epithelial cells

A

hydration of CO2 catalysed by carbonic anhydrase

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19
Q

what will carbonic anhydrase inhibitors produce

A

reduction in the production of aqueous humour

20
Q

what 4 things are required for vision

A
  1. pattern of object must fall onto vision receptors
  2. amount of light entering eye must regulated
  3. light energy must be converted into electrical signals
  4. brain must receive and interpret signals
21
Q

what are the 2 pathways inside the lamina, what are they involved in

A

direct = signal transmission

lateral connections = influence signal processing

22
Q

what cells are involved in the direct pathway (from posterior to superior)

A

photoreceptors
bipolar cells
ganglion cells

23
Q

what cells are involved in the lateral connections, what do they do?

A

horizontal cells = receive input from photoreceptors and projects to other photoreceptor and bipolar cells

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

24
Q

what do photoreceptors do

A

convert light to neural signals in a process known as transduction

25
Q

what are the 2 types of photoreceptors

A

cones

rods

26
Q

what are the 4 regions of a photoreceptor

A

outer segment
inner gement
cell body
synaptic terminal

27
Q

what region of the photoreceptor releases the neurotransmitter

A

synaptic terminal

28
Q

what is the basis of colour vision

A

Light comprises of discrete wavelengths, different opsins can detect specific wavelengths

29
Q

what is visual acuity

A

ability to distinguish between 2 nearby points

30
Q

what is visual acuity determined by

A

photoreceptor space (more dense = better acuity) and refractive power

31
Q

what is the visual acuity of cones

A

high

32
Q

what is the visual acuity of rods

A

low

33
Q

what type of colour vision is seen via rods

A

achromatic (Black and white)

34
Q

what type of colour vision is seen via cones

A

chromatic (colours)

35
Q

where are rods found

A

peripherally

36
Q

where are cones found

A

centrally in the fovea

37
Q

what is the light sensitivity of rods, what does this mean

A

high, used to see in dim light

38
Q

what is the light sensitivity of cones, what does this mean

A

low, used to see in normal light

39
Q

what is the convergence of rods

A

high

40
Q

what is the convergence of cones

A

low

41
Q

when are photoreceptors depolarised

A

in darkness/ no light

42
Q

what happens to photoreceptors when they are exposed to light

A

they become hyperpolarised

43
Q

what is the ‘dark current’ caused by

A

cGMP gated Na+ channel that is open in the dark and closed in the light

44
Q

what is the signal that enables the brain to perceive objects, what causes it

A

change in Na+ due to closing in the presence of light

45
Q

what is the basis of phototransduction

A

light stimulation of rhodopsin leads to activation transducin that activates PDE to hydrolyse cGMP reducing its concentration leading to it to close the cGP gated Na+ channel

46
Q

what is transducin

A

G-protein

47
Q

what is PDE

A

cGMP phosphodiesterase

ophthalmology (7 decks)

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