Lecture 8, 9 and 10 Flashcards

1
Q

What do flat-sheet eyes contain? What do these eyes provide?
What does the pigment layer contain and what does this do?

A

A layer of photoreceptor cells that form a primitive retina
Some sense of light direction and contrast
Contains shading pigment to that helps provide directional information by shading light coding from some directions

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2
Q

What is the retina like in cup-shaped eyes?

A

This folded to form a narrow aperture

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3
Q

What is the lens like in a vesicular eye? What does this mean? What can the lens often do?

A

The lens is inserted into the pinhole aperture.
It collects light from multiple sources and refracts it, thereby focusing it into the retina.
. Often the lens is able to change shape, thereby allowing to focus objects

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4
Q

In convex eyes where can the photoreceptors radiate outwards?what does this form?

A

Radiate outwards from the base, forming a convex rather than a concave, light-gathering surface

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5
Q

What is a single unit of a compound eye called?

A

Ommatidium

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6
Q

Describe how apposition compound eyes work

A

The ommatidia are surrounded by a pigment cell. Each ommatidia operates independently as detects a small part of the environment directly in front of the ommatidium

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7
Q

Describe how superposition compound eyes work and what thy are found in

A

May ommatidia work together to produce a bright, superimposed image. Those eyes are found in nocturnal insects

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8
Q

What does light entering the light pass before striking the retina?

A

Passes through the cores, the aqueous humour, the pupil, the lens m, and the vitreous humour before striking the retina

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9
Q

What is the fovea? What does it provide?

A

Is a pit in the retina which provides the clearest vision

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10
Q

What is the choroid?

A

The vascular layer of the eye (supporting the retina with blood- supply oxygen, energy etc.)

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11
Q

Where are the focal receptor cells located?

A

In the retina

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12
Q

Need to see pages 34/35 about eyes- couldn’t make flashcards about them

A

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13
Q

Where are the photoreceptors (Ross and cones) locates?

A

In the deepest layer of the retina (far away from the light)

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14
Q

What does the retina consist of in cephalopods? How does light strike the photoreceptors?

A

Retina consists of a layer of photoreceptor cells and supporting cells. Light strikes the photoreceptors directly, without passing through multiple layers

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15
Q

Why is there little to no signal processing in the retina of cephalopods?

A

Because there are no interneurons

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16
Q

How did the eye of the cephalopod evolve?

A

Independently of the vertebrate eye

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17
Q

Describe rod photoreceptor cells

A

Contain many photopigments and are therefore very sensitive. They are active under dim light (not during the day). Ross cannot discriminate colours.

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18
Q

Describe come photoreceptors

A

Contain less photopigments than Ross and operate during the day. They are able to detect different colours (wavelength of light)

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19
Q

Where is rhodopsin located?

A

Within the membrane disks of the photoreceptors (rods)

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20
Q

When are vertebrate photoreceptor cells (not invertebrates) depolarised?

A

When they are unstimulated

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21
Q

What does stimulation of the vertebrate photoreceptor do?

A

Causes hyperpolarisation

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22
Q

What do photoreceptor cells release when in the dark?

A

Transmitters (glutamate)

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23
Q

What do touch receptors in Caenorhabditis elegant contain?

A

Mechanosensott neurons with ENaC (epithelial sodium channel) type channels in their membrane

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24
Q

In Caenorhabditis elegant what do mechanical stimuli cause?

A

Extracellular anchors to move relative to the cytoskeleton, pulling on the channel and causing a conformational change that opens or closes the channel

25
Q

What do touch receptors in Drosophila contain?

A

Mechanosensory neurons with TRP channels (transient receptor potential) in their membrane

26
Q

Merkel’s disks are very sensitive what are they important in?

A

Sensing light touch

27
Q

What are Pacinian corpuscles?

A

They are phasic receptors and sensitive to vibrations

28
Q

How do hair follicles work?

A

They detect when a hair is stretched. They are rapidly adapting phasic receptors (e.g. can feel when something is crawling on you but not if it is not moving

29
Q

Describe how Ruffini’s endings work

A

They are sensitive to stretching of the skin. This helps to determine the location of the body (e.g. hitting a snooze button with you eyes closed)

30
Q

What is sound?

A

Is a vibration that propagates as an audible wave of pressure through air or water

31
Q

What does is mean if the frequency or amplitude is higher?

A

The sound is louder

32
Q

How are the ears designed?

A

To capture sound waves and guide the stimulus to cells containing the mechanoreceptors

33
Q

What does the outer ear/ external structures of the ear consist of in mammals?

A

Pinna (which can have different shapes) and the auditory canal

34
Q

What does the middle ear contain? What do they do?

A

Contains a series of small bones (Malleus=hammer, Incus=Anvil and stapes=stirrup) that transfer sound waves to the inner ear

35
Q

What are the names of the 3 small bikes in the middle ear?

A

Malleus=Hammer
Incus=Anvil
Stapes=stirrup

36
Q

What does the stirrup do?

A

Presses a membrane, the oval window, and thereby transmits pressure to the inner ear

37
Q

Because the inner ear is filled with fluid, there is a second membrane (round window) which is important for what?

A

Pressure compensation

38
Q

What is the inner ear? What does it consist of?

A

Is embedded within the skull and consists of a series of fluid-filled membraneous sacs and canals

39
Q

In the inner ear the mechanoreceptors (hair cells) are located between two membranes what are they?

A

The basilar membrane and the tectorial membrane

40
Q

How are the stereocilia connected to each other in hair cells?

A

Connected by tip links

41
Q

Where are mechanosensitive ion channels localised? What are they involved in?

A

Localised near the tips of the stereocilia and are involved in sound transduction

42
Q

What does deformation of the stereocilia lead to? What happens after this?

A

Opening or closing of mechanosensitive ion channels. When the ion channels are open potassium ions will enter the cells

43
Q

Deformation of the stereocilia leads to ion channels opening and potassium ions entering the cell. Why is this?

A

Because the scale media (extracellular environment of the hair cells) contain high amount of potassium

44
Q

Information about sound frequency is specified by what?

A

Which hair cells are activated

45
Q

In the cochlea what do pressure waves do?

A

Waves of different frequencies flex the basilar membrane at different locations

46
Q

What does the base of the inner ear contain?

A

A swelling (ampulla) and a series of sacs including the utricle and the saccule

47
Q

What animals are cochlea found in?

A

Only mammals

48
Q

The mechanoreceptors of the utricle and saccule are found in what structures?

A

The maculae

49
Q

The hair cells of each macula are embedded in what?

A

A gelatinous matrix that is overlain with a series of mineralised otoliths

50
Q

What to the utricle and saccule do?

A

Detect gravity and are important for determining the position of the body

51
Q

What does the semicircular canal in the ear consist of?

A

A fluid filled tube with a swelling (ampulla) at the bottom

52
Q

What is the fluid in the semicircular canal?

A

Is endolymph (high concentrations of potassium)

53
Q

What does the ampulla consist of?

A

A neuromast that senses pressure

54
Q

What are the hair cells in the neuromast embedded in?

A

A cup-shapes gelatinous mass called the cupula

55
Q

What is the most common convex eye? What is a single unit of those eyes called?

A

Compound eyes in Arthropods.

Ommatidium

56
Q

What are the photoreceptors in compound eyes called?

A

Reticular cells

57
Q

What are TRPM8 ion channels involved in?

A

The sensation of environmental cold

58
Q

In snakes where is TRPA1 located? What is it responsible for?

A

Located in trigeminal nerve fibres and responsible for the detection of infrared radiation