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University - Neuroscience > Sensory systems > Flashcards

Sensory systems Flashcards

1
Q

What is the stimulus receptor and location for the modularity, hearing

A

Stimulus - mechanical

Receptor - Mechanoreceptor

Location - cochlea

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2
Q

What is the stimulus receptor and location for the modularity, balance

A

Stimulus - mechanical

Receptor - mechanoreceptor

Location - Vestibular system

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3
Q

What is the stimulus receptor and location for the modularity, vision

A

Stimulus - light

Receptor - Photoreceptor

Location - retina

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4
Q

What is the stimulus receptor and location for the modularity, Touch

A

Stimulus - Mechanical

Receptor - Mechanoreceptor

Location - Skin

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5
Q

What is the stimulus receptor and location for the modularity, Temperature

A

Stimulus - thermal

Receptor - Thermoreceptor

Location - Skin

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6
Q

What is the stimulus receptor and location for the modularity, pain

A

Stimulus - mechanical,thermal and chemical

Receptor - noiceptor

Location - skin, internal organs

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7
Q

What is the stimulus receptor and location for the modularity, proprioception

A

Stimulus - mechanical

Recptor - Mechanoreceptor

Location - mucles, tendons, joints

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8
Q

What is the stimulus receptor and location for the modularity, olfaction

A

Stimulus - chemical

Receptor - Chemoreceptor

Location - nasal cavity

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9
Q

What is the stimulus receptor and location for the modularity, taste

A

Stimulus - chemical

Receptor - Chemoreceptor

Location - Tongue, Pharynx, palate, epiglottis

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10
Q

How does a stimulus allow for the perception of touch

A

Stimulus –> sensory receptor activated –> Membrane permeability is altered in the sense cell –> Receptor potential develops in the sense cell –> neurotransmitter is released onto afferent neuron terminals –> AP is generated in Afferent neuron –> AP propagates to the CNS –> CNS integrates the information

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11
Q

What does the proprioception system do

A

your body’s ability to sense movement, action, and location.

Takes information from Golgi tendon organs and Muscle spindles to tell the CNS how stretched the muscles allowing us not to fall over

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12
Q

What is the difference between a graded receptor potential and an AP

A

GRP increase in size as a response to increases in stimulus

AP are always the same size but have a threshold for activation

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13
Q

What is an example of direct neuronal activation

A

Olfactory receptors

Ion influx causes a GRP to develop in cilium

Large enough receptor potentials cause depolarisation in the soma –> APs travel to olfactory bulb

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14
Q

What is an example of neuronal activity using a synapse

A

Taste receptors

Ion influx causes membrane depolarisation and a GRP develops –> initiates synaptic vesicle to fuse w membrane and neurotransmitter is released –> NT binds to postsynaptic receptors generating an EPSP in the afferent neuron of the dendrite –> big enough EPSPs generate an AP

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15
Q

What is sensory transduction

A

the translation of the sensory stimulus into neuronal activity

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16
Q

What are the 4 types of information that a sensory receptor can convey

A

Modality

Location

Intensity

Timing

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17
Q

What is labelled line code

A

That the receptors are only selective for one type of stimulus energy

Modality specific line of communication

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18
Q

What is synaesthesia

A

When someone senses one modality but perceive it as another modality

A fault in the labelled line code

“Hear colours”

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19
Q

What is stimulus location

A

Spatial arrangement of activated receptors within a sense organ which gives information about the stimulus

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20
Q

What is a receptive field in the somatic field

A

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

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21
Q

What is stimulus intensity

A

The total amount of stimulus energy delivered to the receptor

Lowest stimulus is known as the threshold

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22
Q

When do rapidly adapting receptors respond

A

At the begging and end of a stimulus

Phasic receptors

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23
Q

When do slowly adapting receptors respond

A

Respond to prolonged stimulation

Tonic receptors

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24
Q

What is divergence

A

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

Allows for redundancy

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25
Q

What is convergence

A

Ensures that relay neurons have a larger receptive field than primary afferent neurons

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26
Q

What do inhibitory neurons allow throughout sensory integration

A

Ensures the signal in the most active neuron is propagated

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27
Q

What is the rod photopigment

A

Rhodopsin

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28
Q

What are the cone photopigments

A

S - Short wavelength (420)

M - medium (530

L- Long (560)

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29
Q

What is the retinal ganglion photopigment

A

Melanopsin - plays an important role in non-image-forming visual functions, including hormone secretion, entrainment of circadian rhythms, cognitive and affective processes.

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30
Q

What happens to the membrane potential when photoreceptors are exposed to light

A

They are hyperpolarised

cGMP - gated non selective cation channels are open in the dark allowing an influx of Na+ (dark current) so cell is depolarised

Light decreases levels of cGMP so closes the channels –> prevents Na+ influx –> K+ still leaves the cell –> hyperpolarised

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31
Q

How many photons allow the sensation of light in humans

A

5-7

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32
Q

How is rhodopsin activated

A

Light

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33
Q

What are the two parts of rhodopsin

A

Opsin and retinal

Opsin varies and retinal can change between cis and trans

Opsin is the GPCR

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34
Q

How does photo transduction occur

A

Light (photons) enters the retinal pigment causing a change from cis to trans form –> this changes opsin configuration –> activates transducin (GPCR with alpha, beta and sigma subunits) –> Alpha subunit activates Phosphodiesterase –> PDE cleaves cGMP into GMP –> removing cGMP causes Na+ gates to close so Na+ can’t get into the cell and the cell becomes hyperpolarised –> glutamate release decreases –> Light can be seen

Signal amplification as its an enzyme cascade

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35
Q

Why cant rods process bright lights

A

They become easily saturated and rhodopsin become bleached

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36
Q

What is light adaptation

A

Photoreceptors initially hyperpolarise greatly, photoreceptors then gradually depolarise with continued bright light

Requires calcium

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37
Q

How does light adaptation occur

A

in the dark: Ca2+ enters cells and blocks guanylyl cyclase –> reduces cGMP production so closes some ion channels

In the light, channels are shut so Ca2+ cannot enter cells, this causes the block on guanylyl cyclase to be released –> more cGMP produced so more channels open

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38
Q

What does arrestin do

A

Control GPCR including rhodopsin. Binds to rhodopsin so transducin cant be activated –> stopping the cascade

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39
Q

How are Bipolar cells classified

A

Based on bipolar response to glutamate

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40
Q

How do Bipolar cells turn on and off

A

Photoreceptor hyperpolarises to light –> less glutamate release

Bipolar cells hyperpolarise –> OFF bipolar cell

Bipolar cells depolarise –> ON bipolar cell

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41
Q

What receptor does an OFF bipolar cell use

A

Ionotropic glutamate receptors (positive ions into the cell)
More glutamate released –> binds to receptor which opens K+ channels –> K+ leaves
which hyperpolarises the cell –> releases more glutamate from OFF bipolar cell

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42
Q

What receptor does an ON bipolar cell use

A

GPCR (metabotropic)
Can be inhibitory
Release glutamate in the dark

In the light –> photo receptor hyperpolarises –> reduction in glutamate –> cell depolarises –> releasing more glutamate from ON bipolar cell

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43
Q

What is the organisation of bipolar cells

A

Centre-surround receptive field organisation

allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround

Centre –> direct
Surround –> Horizontal

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44
Q

What is wavelength

A

Distance between peaks or troughs

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45
Q

What is frequency

A

Waves per second

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46
Q

What is amplitude

A

Difference between wave peak and trough

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47
Q

What are the 3 ways that light rays interact

A

Reflection

Absorption

Refraction

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48
Q

What does the pupil do

A

Lets light inside the eye

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49
Q

What does the iris do

A

Contains muscles which control the amount of light entering the eye

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50
Q

What does the cornea do

A

Glassy, transparent covering of the pupil which refracts light

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51
Q

What does the sclera do

A

Continuous with cornea, forms a tough protective wall that gives the eyes shape

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52
Q

What does the extraocular muscles do

A

Move the eyeball, controlled by oculomotor nerve (CNIII) (Cranial Nerve)

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53
Q

What does the optic nerve do

A

Carries axons from retina to brain

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54
Q

What is the optic disk

A

Origin of blood vessels and optic nerve –> cant sense light

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55
Q

What is the macula

A

Region of retina for central vision

Has no large blood vessels to improve vision quality

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56
Q

What is the fovea

A

The highest area of visual acuity

Only cones

57
Q

What does the retina contain

A

Sensory receptor cells and afferent neurons

58
Q

How is stretching and relaxing of the lens enabled

A

Suspended by zonal fibres (ligaments) which attach to the ciliary muscle

Flattened (distant) - SL contract and cillary muscles relax

59
Q

Where does refraction take place

A

Cornea - 80%

Lens - 20%

60
Q

What is degree of refraction determined by

A

Angle of the light in the eye

Difference in refractive indices between the two media

61
Q

How does refraction in the cornea work

A

Light arrives through air but the cornea is mainly water

Light travels slower through water than air causing refraction

62
Q

What is the focal distance

A

The distance from refractive surface to convergence of parallel light rays

63
Q

How does the lens accommodate to see distant objects

A

Lines are almost parallel

Cornea provides sufficient refraction to focus the light rays onto the retina

64
Q

How does the lens accommodate to see close objects

A

Light rays are not parallel

Requires additional refraction to focus them onto the retina

Caused by the fattening of the lens

CM contract, SL relax

65
Q

What does the rounded lens do

A

Increases the refractive power to focus closer objects onto the fovea

66
Q

What does emmetropic mean

A

Perfect vision

67
Q

How is accommodation achieved

A

Contraction and relaxation of the ciliary muscles to move the lens

68
Q

How is the retina organised

A

Laminar organisation

69
Q

What does the retina do

A

Converts focussed light into neural activity

70
Q

What are the 5 cells of the retina

A

Ganglion cells - output from the retina

Amacrine cells - modulate information between GCs and BCs

Bipolar cells - Connect photoreceptors to ganglion cells

Horizontal cells - modulate information between photoreceptors and BCs

Photoreceptors - sensory transducers, both rods and cones

71
Q

What are photoreceptors

A

Membranous disks containing light-sensitive photopigments that absorb light

72
Q

What is the duplicity theory

A

Cant have high sensitivity and high resolution in a single receptor

73
Q

What is the difference between rods and cones

A

Rods - greater number of disks, higher photopigment concentration, 1000x more sensitive to light, enable vision in low light (scotopic), low visual acuity

Cones - enable colour vision, used in daylight (photopic), high visual acuity and lower sensitivty

74
Q

What is the difference between the central and peripheral retinal

A

Central - Low convergence, low sensitivity, high resolution - mainly cones

Peripheral - high convergence, high sensitivity, low resolution - mainly rods

75
Q

Why do cones have high resolution

A

Low convergence on retinal ganglion cells

76
Q

What is the Vitreous humor

A

colourless substance which provides pressure inside the eyeball to maintain its shape

77
Q

Why are some people farsighted

A

The eye is too short

Not enough refraction

78
Q

Why are people nearsighted

A

The eye is too long

Rays are more divergent

Increased refraction

79
Q

What is the chemical sense used for

A

Identifying food sources

Avoid noxious substances

Finding a mate

80
Q

What are the 5 basic tastes

A

Salty - electrolytes - Want high salt content

Sour - H+ content - Avoid high acidity

Sweet - Sugars - High sugar content wanted

Bitter - diverse chemical structures 0 Avoid bitter content

Unami (savoury) - Amino acids - High amino acid preference

81
Q

What are the taste organs

A

Tongue, cheek, soft palate, pharynx, epiglottis

2000-5000 taste buds with 100 chemoreceptive taste cells per taste bud

82
Q

What does the taste pore allow

A

Sensory transduction by microvilli

83
Q

Where are taste buds contained

A

Lingual papillae

84
Q

What tastes require ligand gate ion channels and which require GPCR

A

Salty - sour - bitter are ionotropic

Sweet and unami are metabotropic

85
Q

What is the specificity of taste buds and cells

A

Taste cells only respond to one stimuli whereas taste buds contain many taste cells which respond to various stimuli

86
Q

How are gustatory afferents separate from taste cells

A

Require neurotransmitter release across the synaptic cleft

87
Q

What is capsaicin

A

Receptor on the tongue which detects heat in food

88
Q

What are the 4 parts of the tongue

A

Filli form papillae - middle tongue - texture

Circumvallate - taste - back of the tongue - taste buds in indentation

Foliate papillae - small area - side of tongue

Fongiform - evaginations - top fo the tongue

89
Q

How do we taste

A

100 chemoreceptive taste cells per taste bud

Taste pore allows for sensory transduction by microvilli on apex of taste bud.

Microvilli bind to receptors in the taste cell

Synaptic transmission at base

90
Q

How do odorants reach the olfactory receptor cells

A

Dissolve in the mucus layer

91
Q

Where is transduction machinery found

A

Within the cilia at the end of the dendrite

92
Q

What is the primary afferent neuron of the olfactory system

A

The axon of the receptor cell

93
Q

What are the characteristics of axons in the olfactory system

A

They are hin and unmyelinated

94
Q

What is special about the axons in the olfactory system

A

They are regularly replaced in adults

95
Q

How many odorant receptor proteins are in the body

A

around 350

Olfactory receptor cells only express one odorant receptor

One odorant can recognise multiple odorants

The combination of odorant receptors which recognise an odoront which allows us to recognise a specific odor

96
Q

How does transduction occur

A

via G(olfs)

97
Q

What type of receptor are all ORs

A

GPCR

98
Q

What is the downstream pathway of every OR

A

G(olf) –> adenylyl cyclase –> cAMP –> cyclic nucleotide gated ion channels –> depolarisation –> Ca”+ gated Cl- channels –> further depolarisation

99
Q

What is the difference between an intense stimulus and a large stimulus in the olfactory system

A

Large - threshold for AP firing is reached

Intense - Large receptor potential - increased AP firing rate

100
Q

Where does each glomerulus receive signals from

A

Each glomerulus receives from only one type of olfactory receptor

101
Q

Where do second order neurons of the olfactory system project

A

Olfactory cortex (conscious smell)

Olfactory bulbs

Hypothalamus (sex and neuroendocrine)

Hippocampus (memory)

Amygdala (Emotional response)

Reticular formation (visceral responses)

102
Q

What scale are decibels measured

A

Logarithmic

Amplitude is measured in dB

103
Q

What is the pinna

A

Outer ear - allows brain to hear where on the vertical plane the sound is loated

104
Q

What is the tympanic membrane

A

Middle ear - moves back and forth with ear

TM gets pushed by the compression of a soundwave –> pushes stapes into oval window –> pushes fluid in cochlea –> round window allows for movement of fluid out of tympanic membrane

Movement of fluid stimulates cells to allow them to transfer sound

105
Q

What is the range of human hearing

A

20Hz to 20,000 Hz

106
Q

What are the ossicles of the middle ear

A

Malleus, incus and the stapes

107
Q

How are the ossicles arranged

A

Malleus to incus is a rigid connection

Incus to stapes is a flexible connection

108
Q

What do the ossicles do

A

Amplify the sound to cause 20x more pressure on the oval window than on the tympanic membrane

109
Q

How does the tympanic membrane move

A

TM pushed by the compression phase of the sound wave and pulled by the refraction phase of a sound wave

110
Q

What are the 3 compartments of the cochlea

A

Scala vestibuli - Filled with perilymph and connect slarge end to oval window

Scala tympani - filled with perilymph and connects large end to the round window

Scala media - filled with endolymph - high K+ concentration and high potential

111
Q

What is the anatomy of the basilar membrane

A

Runs from base to apex

Moves up and down with frequency

Basal end is narrower and stiffer

Apex is wider and floppier

112
Q

How does the basilar membrane change with the frequency

A

High frequency moves basal

Low frequency moves apex

113
Q

How does the basilar membrane displacement affect hair cells

A

Stapes moves outward –> basal membrane moves upwards –> hair cells depolarise

Stapes moves inward –> Basal membrane moves downwards –> hair cells hyperpolarise

114
Q

How are hair bundles connected

A

Tip links

115
Q

What are the types of hair cell

A

Inner HC and Outer HC

116
Q

What do tip links do

A

Fine structures, the higher the Db the more stereocilia are firing causing the tip links to be highly stimulated.

In over stimulated hearing loss, Tip links break

Tip links opens a cation channel, scala medium contains lots of potassium –> potassium moves in through tip links –> depolarises –> glutamate released –> afferent neuron activated

117
Q

What do outer hair cells do

A

They act as the cochlear amplifier (low sounds)

As the voltage changes the HCs move –> amplifies movement of the BM –> outer hair cells move with the BM –> hear at a low frequency

118
Q

What is the point of the vestibular system

A

Tells us direction (which way is up and where we are going)

Helps keep our eyes still as we move

Maintains posture

Our ability to perceive our own movement within space

119
Q

What is the vestibular labyrinth filled with

A

Endolymph

120
Q

What is the difference between hair cells of the auditory and vestibular system

A

Hair cells of vestibular respond to lower frequencies

Vestibular hair cells keep their kinocilium throughout life (sets polarity of hair bundle and changes direction of hair growth)

More rows of stereocilia in vestibular

121
Q

What are the two types of vestibular hair cell

A

Type 1 - calyx (post synaptic region which covers the bottom of the hair cell
Type 2 - afferent dendrite

Allows for different properties for communication

122
Q

What are the semi circular canals for

A

Different types of rotation

Horizontal - spinning
Anterior
Posterior - moving up while sitting

123
Q

What is the ampulla

A

Where mechanotransduction machinery is (HCs)

One ampulla per semi-circular canal

124
Q

What are the otolith organs

A

Detect linear motion

Utriculi - Linear acceleration

Saccule - Up and down

125
Q

What is the utricle and saccule filled with

A

Endolymph

126
Q

What direction do hair cells move to become excitated

A

To the right, tips tighten, Voltage gated Ca2+ channels at the base cause the release of glutamate. Glutamate activates Glutamate receptors on afferent neurons.
Generates EPSPs –> summate to become APs –> neurotransmitter is released –> increase the frequency of impulses onto the nerve

127
Q

How do the hair bundles allow for hyperpolarisation

A

Few channels are open

128
Q

What is the range of the vestibular system

A

0-20Hz

129
Q

Where are hair cells found in the vestibular system

A

In the macula

130
Q

What is the otoconia

A

Part of the vestibular system which moves with gravity to open or close ion channels

131
Q

What is the orientation of hair cells in the vestibular system

A

Has a line where hair cells face one way and then the opposite on the other side

Auditory has same orientation throughout

132
Q

How do you tell if there changes in the vestibular system are due to head tilt or linear acceleration

A

Vision

Propriosensors - muscle stretch

133
Q

What is the cupula

A

A gelatinous structure penetrated by hair bundles used for sensing torsional movements of the head

134
Q

What do the semicircular canals detect

A

Angular acceleration (rotation)

The inertia of endolymph during rotation displaces the cupula

135
Q

How do semicircular canals work

A

Either side of the head do opposite things

Work in pairs (redundancy)

If head moves to the left, there will be increased firing on the left side and a decreased firing on the right side

Hair bundles move to the shorter stereocilia and get inhibited which decreases the firing

136
Q

How is the vestibulo-ocular reflex activated

A

Movement activates hair cells –> brainstem communicates with ocular motor –> pulls eyes in opposite direction to movement

137
Q

What is nystagmus

A

The resetting of eye rotation by moving (involuntarily from side to side)

138
Q

Why do you still feel like you are spinning after stopping

A

Endolymph takes a while to stop after rotation has finished

139
Q

What is the purpose of the vestibular ocular reflex

A

Stabilise gaze by countering the movement of the head

University - Neuroscience (9 decks)

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