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PA10315 > Ears and eyes > Flashcards

Ears and eyes Flashcards

1
Q

What is the optic nerve?

A

A sensory nerve.

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2
Q

What is the oculomotor nerve?

A

The output nerve from the brain back to the eye.

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3
Q

What happens if the ciliary muscle in the eye is contracted?

A

releases tension on the zonular fibres, which allows lens to return to a spherical shape
Focus on close objects

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4
Q

What happens if the ciliary muscle is relaxed?

A

zonular fibres pull lens into flattened, oval shape

Focus on distant objects

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5
Q

What is shortsightedness?

A

When the eyeball is too long and the lens is too rounded

can’t focus on far objects.

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6
Q

What is longsightedness?

A

The eyeball is slightly too flat.

Can’t focus on near objects

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7
Q

What is cataracts?

A

When the lens becomes cloudy.

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8
Q

What is glycoma?

A

Too much pressure inside the eyeball.

can damage the retina

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9
Q

What are the two possible causes for glycoma?

A

Too much fluid (aqueous humour) may be being produced or the draining process may not be occurring correctly.

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10
Q

What are the two treatments for glycoma?

A

Prostaglandin analogues to increase the drainage or beta-blockers to decrease production of the fluid.

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11
Q

What do rods do?

A

Perceive light and dark.

sensitive and respond well to low light

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12
Q

What do cones do?

A

Perceive red/green/blue light.

respond to bright light

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13
Q

How are neurones in the eye different to other neurones?

A

They constantly fire action potentials in the dark - a silent neurone is firing action potentials.

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14
Q

How does light change the way the neurones act?

A

Light causes the molecules in redopsin receptors to change shape and the the cell becomes less depolarised and is less likely to fire action potentials when light is present.

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15
Q

What happens to rods if they are constantly exposed to light?

A

They become bleached.

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16
Q

How is the input from the eyes to the brain different to the body?

A

The right side of the brain receives a little bit of input from the right eye and vice versa for the left side due to the overlap of the left and right visual fields.

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17
Q

Why can you not see colour in the dark?

A

Cones can only function in bright light conditions.

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18
Q

How does colourblindness arise?

A

The wavelengths of the different cones overlap as the cones are slightly different to normal.

19
Q

What is the difference between the primary visual cortex and the secondary visual cortex?

A

The primary receives input from the eyes and the secondary interpret what our eyes are telling us to see.

20
Q

What does the frontal lobe association area/cortex do?

A

Interprets our emotion from the images we see and can tell us whether something should be feared.

21
Q

What does the chochlea do?

A

Turns vibrations into sound. The fluid in the cochlea vibrates and hair cells respond to the sound coming into the ear.

22
Q

What is the cochlea?

A

The fluid filled inner ear.

23
Q

What are the semi-circular canals of the vestibular involved in?

A

Balance.

24
Q

How is the sensation of dizziness created?

A

When spinning around, the fluid in the vestibular continues moving which creates the sensation.

25
Q

Why does motion sickness occur?

A

There is a sensory mismatch, as our eyes tell us we’re stationary but the vestibular apparatus is activated.

26
Q

What are antihistamines?

A

Antagonists of histamine receptors that are involved in motion sickness.

27
Q

What can antihistamines be used to treat?

A

Sleep, hayfever, motion sickness.

28
Q

What is the difference between antihistamines used to treat motion sickness and sleep and those used to treat hayfever?

A

In motion sickness and sleep the antihistamines need to be able to cross the blood-brain barrier.

29
Q

binocular zone

A

where left and right visual fields overlap

30
Q

auditory vestibular nerve

A

provides input from ears

31
Q

What is the shape of the lens controlled by and how does it work

A

ciliary muscle
stimulated by parasympathetic nerve, contracts and lessens tension on the zonular fibres
makes the lens more spherical and more refraction (closer objects)

32
Q

why does light refract when passing into the eye

A

because the cornea is denser than air

33
Q

Macular degeneration

A

loss of vision in centre of visual field

34
Q

detached retina

A

retina becomes physically detached from the back of the eyeball

35
Q

what type of cells are rods and cones

A

photoreceptors

36
Q

what happens when rods and cones are stimulated

A

light signal converted into electrical through interaction of rods and cones with bipolar and ganglion cells

37
Q

in the absence of light

A

action of guanylyl cyclase converts GTP into cGMP
cGMP binds to cation channels and opens them
Na+ and Ca2+ flow in
The cell maintains a relatively depolarised state

38
Q

In the presence of light

A

Light strikes retinal, which changes in conformation and dissociates from opsin
There is an interaction between opsin and transducin and transducin activates cGMP-phosphodiesterase, which degrades cGMP
A decrease in cGMP means cation channels close, so hyperpolarization occurs

39
Q

what is the first step of hearing

A

the entrance of soundwaves into the external auditory canal, which amplifies and directs sound
Air molecules push up against the tympanic membrane and cause it to vibrate at the same frequency as a soundwave
The temporal membrane separates the auditory canal from the middle ear

40
Q

what are the receptor cells of the organ of corti (cochlea) called

A

hair cells

41
Q

what are the hair cells

A

mechanoreceptors that have hair-like stereocilia protruding from one end.
Movement of the tectorial membrane with sound waves moves cilia on the hair cells and effects neurotransmitter release by the hair cells

42
Q

where are hair cells also found (excluding cochlea)

A

vestibular system

43
Q

function of hair cells in vestibular system

A

detect changes in motion and position of head by stereocilia transduction mechanism similar to that of cochlear hair cells

44
Q

A rounded lens refracts more/less?

A

more

PA10315 (47 decks)

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