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Introduction to neuroscience > Sensory neuroscience > Flashcards

Sensory neuroscience Flashcards

1
Q

What are the 5 traditional senses? What are the 4 other extra ones?

A

Vision, smell. taste, hearing, touch

Balance, proprioception, thermal and pain

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2
Q

What are the four types of information sensory receptors can convery?

A

Modality, location, intensity, timing

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3
Q

What is the labelled line code?

A

How stimulus modality is coded
Receptor is selective for one type of stimulus energy
Axons of receptor/afferent neuron acts as a modality specific line of communication
These make connections with specific areas in the CNS

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4
Q

What is a receptive field in the somatic system?

A

The region of skin innervated by the terminals of the receptor neuron

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5
Q

What is a receptive field in the visual system?

A

The region of the visual field projected onto a photoreceptor

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6
Q

How is stimulus intensity coded?

A

Firing frequency of afferent neurons

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7
Q

How is stimulus location coded?

A

Receptive fields

Different sizes depending on what part of the body

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8
Q

How is onset timing of the stimulus determined?

A

When the stimulus energy is received by the receptor and causes it to fire

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9
Q

How is the stimulus duration determined? What is adaptation?

A

By adaptation rates of receptors

When continuous stimuli causes the firing rate of APs to decrease in response

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10
Q

What are tonic receptors?

A

Slowly adapting receptors responding to prolonged stimulation

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11
Q

What are phasic receptors?

A

Rapidly adapting receptors responding at the beginning and end of a stimulus

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12
Q

Why do we need divergence in terms of sensory integration?

A

Allows primary afferent neurons to signal to more than one relay neuron

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13
Q

Why do we need convergence in terms of sensory integration?

A

Ensures that relay neurons have larger receptive fields than primary afferent neurons

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14
Q

What role do inhibitory neurons play in sensory integration?

A

They ensure the signal in the most active neuron is propagated- lateral inhibition

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15
Q

When are rods used? What is the photo-pigment in them?

A

Under conditions of dark adaptation

Rhodopsin

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16
Q

When are cones used? What photo pigments allow them to do this?

A

Under conditions of light adaptation

Opsins S, M, L

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17
Q

What is the dark current? What property does this give photoreceptors?

A

An Na+ influx caused by cGMP-gated non-selective cation channels that are open in the dark
Means they are depolarized in the dark

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18
Q

What is the photo pigment in the retinal ganglion? What does it control?

A

Melanopsin

Doesn’t produce a clear image, only gives idea of light/dark to drive sleep/wake cycle

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19
Q

What happens to photo receptors when there is light?

A

Light decreases cGMP levels which closes the channels that maintain the dark current
This prevents the Na+ influx so the receptors become hyperpolarised

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20
Q

Phototransduction signal amplification

A

Rhodopsin is activated by light
Stimulates G-protein Transducin to become transducin GTP
The alpha subunit activates enzyme phosphodiesterase (PDE) which reduces cGMP levels and closes the Na+ channels

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21
Q

What enzyme produces cGMP constantly when in the dark?

A

Guanylyl cyclase

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22
Q

What are the differences in saturation between rods and cones?

A

Rods cannot process bright light as they become easily saturated
Cones are not saturated as easily so are used in bright light

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23
Q

Why are rods more easily saturated?

A

Rhodopsin is bleached

cGMP levels are so low that no additional hyperpolarisation can occur

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24
Q

What role does Ca2+ play in adaptation in the dark?

A

Ca2+ normally enters cells and blocks guanylyl cyclase

Reduces cGMP production so some channels are closed

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25
Q

What role does Ca2+ play in adaptation in the light?

A

Channels are shut so Ca2+ cannot enter cells and block guanylyl cyclase
More cGMP is produced so more channels are opened

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26
Q

What happens in terms of neurotransmitters when a photo receptor hyperpolarises in response to light? Why?

A

Reduced glutamate release

In the dark constant depolarization means constant glutamate release

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27
Q

What are bipolar cells?

A

Main retinal interneurons that provide a pathway between receptors and ganglion cells
Two types- ON and OFF

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28
Q

How do OFF bipolar cells respond to glutamate?

A

Hyperpolarise when there is a reduction in glutamate

Switched off by light as they use ionotropic glutamate receptors

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29
Q

How do ON bipolar cells respond to glutamate?

A

Depolarize when there is a reduction in glutamate

Switched ON by light as they use metabotropic glutamate receptors

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30
Q

How are bipolar cells organised? Why?

A

Centre-surround organisation
Connected to photo receptors with horizontal cells above
Gives bipolar cells centre-surround receptive fields

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31
Q

Why is the visual system important?

A

Allows us to detect prey/source food, detect predators/danger, detect mates, communicate

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32
Q

Wavelength

A

Distance between peaks or troughs

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33
Q

Frequency

A

Number of waves per second

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34
Q

Amplitude

A

Difference between wave peak and trough

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35
Q

What three ways do light rays interact with the environment?

A

Reflection, refraction, absorption

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36
Q

Why does refraction occur?

A

Speed of light differs between mediums of different densities

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37
Q

What is the function of the pupil and iris?

A

Pupil- lets light inside the eye

Iris- contains muscles which control amoutn of light entering the eye

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38
Q

What is the function of the cornea?

A

Glassy transparent covering of pupil and iris that refracts light

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39
Q

What is the function of the sclera?

A

Continuous with cornea and forms the tough protective wall of the eyeball to give it its shape

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40
Q

What do the extraocular muscles do?

A

Move the eyeball

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41
Q

What are the two nerves that are involved with the eye?

A

Optic nerve or cranial nerve II- carries axons from the retina to the brain
Oculomotor nerve or cranial nerve III- controls the extraocular muscles

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42
Q

What is the optic disc?

A

Origin of blood vessels and optic nerve, cannot sense light (blindspot)

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43
Q

What is the macula?

A

Region of retina for central vision and is devoid of large blood vessels to improve visual quality

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44
Q

What is the fovea?

A

Thinnest region of the retina, area of highest visual acuity

Contains most of the cones and no rods

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45
Q

What parts of the eye help the lens to function correctly?

A

Zonal fibre suspend the lens

Ciliary muscles enable the stretching of the lens for accommodation

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46
Q

Where does refraction onto the retina occur and in what amounts?

A

80% at the cornea

20% at the lens

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47
Q

What is the degree of refraction determined by

A

Difference in refractive indices between the two media

The angle at which light hits the interface between these two media

48
Q

How is light refracted by the cornea?

A

Light arrives at the cornea by air but the cornea is mainly water so light will travel more slowly through the cornea
Light that hits the cornea directly perpendicular will move straight through onto the retina

49
Q

What is the focal distance?

A

Distance from refractive surface to convergence of parallel light rays

50
Q

When does the lens have to change shape? Why?

A

When objects are closer up as light rays are not parallel and require additional refraction to focus them on the retina

51
Q

Eye when focusing on distant objects

A

Relaxed ciliary muscles
Taut suspensory ligaments
Flattened, weak lens

52
Q

Eye when focusing on closer objects

A

Contracted ciliary muscles
Slackened suspensory ligaments
Rounded, strong lens

53
Q

What is hyperopia and how is it corrected?

A

Lens is too flat/ eyeball is too short so image is focused behind the retina
Convex lenses

54
Q

What is myopia and how is it corrected?

A

Lens is too rounded/ eyeball is too long so image is focused in front of the retina
Concave lenses

55
Q

In what order does light pass through the retina?

A

Ganglion cells > bipolar cells > photo receptor cells

56
Q

What do the nuclear and plexiform cell layers in the retina do?

A

Nuclear- contain cell bodies

Plexiform- regions where synaptic connections occur

57
Q

What are retinal ganglion cells and what do they do?

A

Receive photo sensory information and output this

58
Q

What do amacrine cells do?

A

Modulate information transfer between ganglion cells and bipolar cells

59
Q

What do bipolar cells do?

A

Connect photo receptors to ganglion cells by either hyperpolarising or depolarising in repsonse to reduced glutamate release from photoreceptors

60
Q

What do horizontal cells do?

A

Modulate information transfer between photo receptors and bipolar cells

61
Q

What is duplicity theory?

A

You cannot have high sensitivity and high resolution in a single receptor
Separate systems for monochrome and color

62
Q

Rod structure

A

Greater number of discs
Higher photo pigment concentration so more sensitive to light than cones
Low visual acuity/ resolution

63
Q

Cone structure

A

Fewer discs
Enable color vision, lower sensitivity
High visual acuity/resolution

64
Q

What are the functions of the chemical senses?

A

Identify food sources
Avoid noxious substances
Find a mate or mark territories

65
Q

What are the 5 basic tastes?

A

Salty, sour, sweet, bitter, umami (savoury)

66
Q

What are the taste organs?

A

Primarily tongue, cheeks, soft palate, pharynx, epiglottis

67
Q

What are lingual papillae? What types are there?

A

Contain taste buds which are groups of taste cells
Filiform- spiked, no taste buds, sense texture
Foliate- ridges
Fungiform- mushrooms, at sides and front
Circumvallate- pimples, large

68
Q

How do olfactory receptor cells work?

A

Odorants must dissolve in the mucus layer to reach olfactory receptor cells
Transduction machinery is found within cilia at the end of the dendrite
The primary afferent neuron = axon of receptor

69
Q

Characteristics of olfactory receptor cells

A

Bipolar chemoreceptive neurons
Thin, unmyelinated axons
Regularly replaced

70
Q

How many odorant receptor proteins do humans have? What kind of receptor are they?

A

350

G-protein coupled receptors

71
Q

Odorant receptor Golf pathway

A

Golf > adenylyl cyclase > cAMP > cyclic nucleotide gated ion channels > depolarisation > Ca2+ gated Cl- channels > further depolarisation

72
Q

Convergence of olfactory information

A

Each glomerulus of the olfactory bulb receives input from only one type of olfactory receptor
so there is convergence on secondary neurons

73
Q

What regulates sleep?

A

Raphe nucleus, brain stem and the locus coeruleus

74
Q

What regulates the timing of sleep (not sleep itself)?

A

Superchiasmatic nucleus in the anterior hypothalamus

75
Q

What is human’s physiological range of frequency for sound?

A

20Hz-20,000Hz

76
Q

What is the high risk threshold? What is the threshold of pain?

A

120dB

140dB

77
Q

What are the three ossicles from outer to inner?

A

Malleus
Incus
Stapes

78
Q

What is the function of the outer ear/pinna?

A

Helps the brain to understand where the sound is coming from on the vertical plane
Reason for convoluted shape

79
Q

What is the tympanic membrane?

A

Large drum that vibrates backwards and forwards as sound hits it

80
Q

What structures are in the middle ear?

A

Tympanic membrane
Ossicles
Oval window

81
Q

What is the functional significance of the middle ear?

A

To amplify sound to overcome the greater impedance of cochlea fluid

82
Q

What is perilymph?

A

The fluid that the scala vestibuli and scala tympani are filled with- the canals which surround the cochlea

83
Q

What is endolymph?

A

Fluid that the scala media is filled with- the inside of the cochlea

84
Q

What is the difference between perilymph and endolymph in terms of composition? Why?

A

Perilymph has a composition similar to regular plasma

Endolymph is high in K so cells have a higher potential as this is where the hair cells are

85
Q

How do the ossicles amplify sound onto the oval window?

A

The malleus and incus have a rigid connection to each other but the stapes connection is flexible
Acts as a lever system

86
Q

What happens to the ossicles when the tympanic membrane moves inwards?

A

Bottom of malleus moves down

Pulls incus inwards which pushes stapes inwards onto the oval window

87
Q

Where are auditory hair cells located and how are they organised?

A

Organ of corti
On the basilar membrane
Below the tectorial membrane
3 rows of outer hair cells and 1 row of inner hair cells

88
Q

Anatomy of the basilar membrane and how this relates to frequencies

A

Base- narrow, thick, stiff (high)

Apex- wide, thin, floppier (low)

89
Q

What is the tonotopic map?

A

Different frequencies of sound cause maximal displacement of the basilar membrane in different regions
High at basal end
Low at apical end

90
Q

How does basilar membrane displacement affect hair cells when there is sound?

A

Stapes moves inwards and hits oval window
Basilar membrane moves upwards
Inner hair cell tip links move towards the kinocilium so that TMC1 channels are pulled open
K+ moves into cells from endolymph
Cells depolarise and send signals to primary afferent nerve

91
Q

How does basilar membrane movement affect hair cells when there is no sound?

A

Basilar membrane moves downwards
Inner air cell tip links move so that TMC1 channels close
K+ no longer moves in and cells are hyperpolarised so no signal

92
Q

How do the functions of inner and outer hair cells differ?

A

Inner- have tip links between steriocillia which allows them to be the mechanoelectrical transducers
Outer- electromotile and act as cochlear amplifiers

93
Q

What is electromotility?

A

Changes in electrical profile means they become motile (dance) to amplify the movement of the basilar membrane

94
Q

What are the three semicircular canals of the vestibular system? What do they control?

A

Anterior vertical
Posterior vertical
Horizontal
Head rotation (one for each direction)

95
Q

What are the otolith organs? What do they control?

A

Utricle- forward and backward movement

Saccule- up and down

96
Q

How is the vestibular system organised in terms of perilymph and endolymph?

A

Vestibular labyrinth is filled with endolymph with chambers either side filled with perilymph

97
Q

What are the ampullas?

A

Area at the base of each semicircular canal when the mechanotransduction machinery is

98
Q

How does the movement of hair bundles cause glutamate release?

A

Hair bundles move towards the kinocilium and subsequent tip links which opens k+ channels
Graded potentials cause Ca2+ channels to open which allow glutamate to be released
Generates EPSPs

99
Q

What are the differences between the hair cells of the vestibular and auditory systems?

A

Vestibular- more rows of hairs, respond to lower frequencies, keep their kinocilium throughout life to maintain polarity

100
Q

What are the two types of vestibular hair cells? What is the difference?

A

Type 1- calyx which encompasses whole bottom of the cell which means communication is different
Type 2- normal communication

101
Q

What parts of the saccule and utricle are the hair cells found?

A

Sensory patches called macula

102
Q

What is the striola?

A

A curved line formed from hair cells pointing toward it or away from it
When cells on one side are activated the ones on the other side are inhibited

103
Q

What is the otolithic membrane?

A

Membrane resting on top of the hair cells

Gelatinous and has otoconia in it

104
Q

What is otoconia?

A

Calcium carbonate crystals which add weight

Weight means the hair cells are pulled in given direction when the otolithic membrane moves

105
Q

How does the CNS distinguish tilting and moving in a given direction? (same signal output)

A

Integration of information from the visual system

106
Q

What is the cupula?

A

Gelatinous structure penetrated by hair bundles in the ampulla at the base of each semicircular canal

107
Q

How is angular acceleration (rotation) detected by the semicircular canals?

A

Inertia of endolymph during rotation displaces the cupula
Hair bundles deflected
Firing of sensory fibres depending on what side of the head- they work in pairs as they are on the same plane
Opposite side is decreased

108
Q

What is the vestibulo-ocular reflex?

A

Gaze-stabilizing reflex that allows your eye movements to coordinate with motion so that your vision is stable

109
Q

What is vestibular nystagmus?

A

Biphasic eye movement that enables the resetting of eye position during sustained head rotation
Slow phase- eyes rotate in opposite direction to head movement
Quick phase- rapid resetting movement back to centre of gaze

110
Q

What is the receptor for salty simuli? What kind of receptor is it?

A

ENaC

Ion channel

111
Q

What is the receptor for sour simuli? What kind of receptor is it?

A

OTOP1

Ion channel

112
Q

What is the receptor for sweet simuli? What kind of receptor is it?

A

T1R2 and T1R3

GPCR

113
Q

What is the receptor for umami simuli? What kind of receptor is it?

A

T1R1 and T1R3

GPCR

114
Q

What is the receptor for bitter simuli? What kind of receptor is it?

A

T2Rs

GPCR

115
Q

Girls and boys hate pedos

A 
Ganglion 
Amicrine
Bipolar
Horizontal
Photoreceptors

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