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PA10315 COPY > 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
  1. releases tension on the zonular fibres
  2. which allows lens to return to a spherical shape
  3. More refraction
  4. Focus on close objects
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4
Q

What happens if the ciliary muscle is relaxed?

A
  1. zonular fibres pull lens into flattened, oval shape

2. Focus on distant objects

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5
Q

What is shortsightedness?

With age, ‘accommodation’ declines. This is when you try and focus on a near object… the lens needs to get more rounded. With age, the ability of the lens to do this decreases. This is why many older people need reading glasses.

A
  1. When the eyeball is too long and the lens is too rounded

2. can’t focus on far objects.

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6
Q

What is longsightedness?

A
  1. The eyeball is slightly too flat.
  2. Can’t focus on near objects
  3. With age, ‘accommodation’ declines.
  4. This is when you try and focus on a near object and the lens needs to get more rounded.
  5. With age, the ability of the lens to do this decreases. 6. This is why many older people need reading glasses.
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7
Q

What is cataracts?

A
  1. When the lens becomes cloudy.

2. Can be remedied with surgery.

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8
Q

What is glycoma?

A
  1. The eye ball is full of fluid (vitrous humour)
  2. Too much pressure inside the eyeball.
  3. Can damage the retina
  4. Age-related and also has a genetic component (more likely to get it if a close family member has it).
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9
Q

What are the two possible causes for glycoma?

A
  1. Too much fluid (aqueous humour) may be being produced

2. or the draining process may not be occurring correctly.

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10
Q

What are the two treatments for glycoma?

A
  1. Prostaglandin analogues to increase the drainage
  2. Beta-blocker eye drops to decrease production of the fluid.
  3. If left untreated it can cause blindness because the increased pressure in the eye damages the retina.
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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
  1. 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
  1. 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
  1. Colour blindness is caused by people having slightly different cones (retinal cells that respond to light of different colours),
  2. where the colours that they respond to overlap in terms of wavelength/colour
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19
Q

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

A
  1. The primary receives input from the eyes reaches the brain
  2. secondary (occipital lobe association area and parietal lobe association area) interpret what our eyes are telling us to see.
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20
Q

What does the frontal lobe association area/cortex do?

A
  1. Interprets our emotion from the images we see and can tell us whether something should be feared.
21
Q

How does sound enter the ear?

A
  1. The sound waves in the air enter the ear
  2. Which causes vibration of the tympanic membrane (ear drum)
  3. This then vibrates the 3 small inner-ear bones
  4. Which then vibrate the cochlea
22
Q

What is the cochlea and what does it do?

A
  1. The fluid filled inner ear.
  2. Turns vibrations into sound.
  3. The fluid in the cochlea vibrates and hair cells respond to the sound coming into the ear.
23
Q

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

A
  1. Sense of balance
  2. There are 3 semicircular canals, full of fluid. When our head moves, the fluid in these canals move
  3. Have hair cells
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
  1. There is a sensory mismatch, as our eyes tell us we’re stationary
  2. But the vestibular apparatus is activated and telling our brain that our head is moving
26
Q

What are antihistamines?

A
  1. Antagonists of histamine receptors that are involved in motion sickness.
  2. Can be used to help with sleep, hayfever, motion sickness.
  3. Inhibit receptors in the brain
27
Q

What can be used to treat motion sickness

A
  1. muscarinic receptor antagonists

2. histamine receptor antagonists

28
Q

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

A
  1. In motion sickness and sleep the antihistamines need to be able to cross the blood-brain barrier.
  2. Newer ones (eg. cetirizine) don’t cross the blood-brain barrier as much and so are effective to treat peripheral immune responses (eg. hay fever, insect bites) but not motion sickness
29
Q

binocular zone

A
  1. where left and right visual fields overlap
  2. Input from the retinal cells goes to the primary visual cortex. The right visual cortex receives input from the left visual field, and vice versa
30
Q

auditory vestibular nerve

A
  1. provides input from ears
31
Q

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

A
  1. ciliary muscle
  2. stimulated by parasympathetic nerve, contracts and lessens tension on the zonular fibres
  3. makes the lens more spherical and more refraction (closer objects)
32
Q

why does light refract when passing into the eye

A
  1. because the cornea is denser than air
33
Q

Macular degeneration

A
  1. loss of vision in centre of visual field
  2. Degeneration of the retina.
  3. Often age-related but of unknown cause.
  4. No real treatments available
34
Q

detached retina

A
  1. retina becomes physically detached from the back of the eyeball
  2. generally age- or trauma-related
  3. Can be remedied with surgery.
35
Q

what type of cells are rods and cones

A

photoreceptors

36
Q

what happens when rods and cones are stimulated

A
  1. light signal converted into electrical through interaction of rods and cones with bipolar and ganglion cells
37
Q

what is the first step of hearing

A
  1. the entrance of soundwaves into the external auditory canal, which amplifies and directs sound
  2. Air molecules push up against the tympanic membrane and cause it to vibrate at the same frequency as a soundwave
  3. The temporal membrane separates the auditory canal from the middle ear
38
Q

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

A
  1. hair cells
39
Q

what are the hair cells and what are their function

A
  1. mechanoreceptors that have hair-like stereocilia protruding from one end.
  2. The fluid in the cochlea vibrates the hair cells.
  3. When the hairs on the hair cells move, they open ion channels which causes the cell to depolarize.
  4. This then causes release of neurotransmitters onto neurons, these fire action potentials and project to the auditory cortex.
40
Q

where are hair cells also found (excluding cochlea)

A
  1. vestibular system
  2. Detect changes in motion and position of head by stereocilia transduction mechanism similar to that of cochlear hair cells
41
Q

A rounded lens refracts more/less?

A

more

42
Q

How do we see things

A
  1. We see things as light reflects from objects.
  2. Light waves have a wavelength of between around 400 and 750 nanometres.
  3. Long wavelengths are lower energy and are towards the red end of the colour spectrum
  4. Short wavelengths are higher energy and are towards the violet end of the colour spectrum
  5. Light waves are refracted by the lens of the eye to form a focussed picture on the retina (where the sight receptors are)
  6. Light activates GPCRs in the retina, which affects how many action potential the retinal cells generate
43
Q

What are sounds caused by and what is the range of frequency of human hearing

A
  1. Sounds are caused by waves
  2. Between around 20 and 20,000 Hz (waves per second)
  3. The higher the frequency of the wave, the higher the pitch of the sound
  4. The higher the amplitude, the higher the loudness of the sound

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44
Q

Name 6 hearing problem causes

A
  1. Excess wax in ear canal
  2. Outer ear infection
  3. Middle ear infection
  4. Bunged up Eustachian tube
  5. Inner ear infection
  6. Destruction of cilia in the cochlea
45
Q

Describe how to treat Excess wax in ear canal

A
  1. Can have ears syringed, or can use oil to soften wax and allow it to flow out of ear
46
Q

Describe how to treat Outer, middle and inner ear infection

A
  1. often caused by a virus (treatment – rest and plenty of fluids)
  2. sometime bacterial (treatment – antibiotics)
  3. Middle and inner ear infections can also cause dizziness, not just temporary hearing loss, as it also can affect the vestibular apparatus
47
Q

Describe causes of Bunged up Eustachian tube

A
  1. often with a cold, or, pressure changes (eg. on a plane)
48
Q

Describe causes of the destruction of cilia in the cochlea

A
  1. Caused by loud noise, or, age-related

2. Generally irreversible

PA10315 COPY (48 decks)

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