Special Senses Flashcards

1
Q

What is the stimulus for vision?

A

Light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is special about light that results in vision?

A

The only thing special about light is that we have special receptors that can interact with light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the units for visual wavelengths?

A

Nanometers

nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What wavelengths are our photoreceptors receptive to?

A

Approximately 400-750nm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do we perceive variations in wavelength as?

A

Changes in colour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do we perceive variations in amplitude of wavelengths as?

A

Changes in brightness/intensity of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the job of the visual system?

A

To detect visible radiation and use it as a basis for formation of visual perceptions of the world to guide behaviour

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the special structure for light?

A

The Eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What makes special senses special?

A

They are all a result of a unique structure that house the particular receptor - whereas other systems have the receptor all over the body.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the two basic components of the eye and their job?

A

An optical component that has the main job of collecting and focusing light into the plane of the retina.

A neural component that converts energy of light into patterned change of membrane potential that OTHER parts of the brain can decode to generate visual perceptions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the retina part of?

A

The Brain / part of the CNS.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why do we have a blind spot?

A

Because there are no photoreceptors on top of the optic disc where the optic nerve opening is (retina is not continuous).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where is the optic nerve located?

A

Back of the eye on the side closest to the nose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the sclera?

A

The whites of the eye.

it is a fibrous capsule.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the pigmented disc of the eye?

A

The iris - what gives eye its colour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the black spot in iris?

A

Pupil

Pupil is perceive as a black spot but it is actually a hole in the iris. What we are seeing is black pigment at the back of the eye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What prevents internal reflections?

A

The black pigment at the back of the eye (what we see are the pupil).

Black absorbs all wavelengths and reflects nothing therefore no internal reflections. Because there is no light reflecting off the black pigment it means we can localise where light is coming from = locality.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the Cornea?

A

The transparent structure in front of the iris.

Transparent because it is avascular (meaning it does not have any blood vessel and gets nutrients via transfusion from surrounding vessels).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Draw the major structures of the eye.

A

Refer to slide image.

Should include:
Cornea
Aqueous humor
Anterior chamber
Iris
Lens
Posterior Chamber
Zonule Fibers
Cilary body
Sclera
Viteous humor
Retina
Fovea
Optic disc
Optic nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the anterior chamber?

A

Structure that is filled with aqueous humor fluid.

It keeps pressure in the eye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What continuously produces aqueous humor?

A

Cilary body.

As aqueous humor is continuously produced it is also continuously drained away.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the characteristics of the lens?

A

A fibrous capsule filled with crystallised cells.

It is avascular.

It is slightly elastic and flexible meaning the shape of the lens can change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are ligaments attaching the lens to the ciliary body called?

A

Zonule Fibres.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is composition of the ciliary body?

A

Smooth muscle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the vitreous humor?

A

The majority of the eye.

Mostly a solution of transparent protein - no tissues of cells in this area.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the optic disc?

A

Head of the optic nerve - where axons leave the back of the eye and go to visual centres in the brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the fovea?

A

A area of the retina.

It has the highest 2 point discrimination - bit of the brain/retina we use when we focus on something.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is refraction?

A

Bending of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What does refraction result in?

A

Upside down and back to front.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is refraction related to?

A

The difference between the refractive indices of the two media, and to the curvature of the refractive surface.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the refractive index of water and why is this important?

A

1.333

Light coming from the air first hits water (tear drops that surround our eye) - the refractive index of air is 1.000. This change means that majority of refraction occurs when light goes from air to water because it is the biggest change in refractive index - most other areas of the eye have about the same refractive index as water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is refractive power?

A

Refractive power is the reciprocal of focal length in meters.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is refractive power measured in?

A

Diopters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the focal point of a “relaxed” eye?

A

About 1.7cm (1/60).

Because the relaxed eye has a total refractive power of about 60 diopters.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What would the effect of a lens having more diopters be?

A

The more diopters a lens has, the closer it brings the light to a focus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What are the three process of the “near response” that occur as you shift your gaze from distant to near objects?

A

(1) Accomodation
(2) Constriction of pupil
(3) Convergence of eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is accomodation?

A

Contraction/relaxation of ciliary muscle to alter lens shape and change refractive power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is happening during convergence of eyes?

A

(E.g., cross eyed).

Convergence of the eyes refers to the coordinated movement of both eyes towards each other to maintain focus on an object as it moves closer to the observer.

Object remain in register on corresponding parts of the two retinae.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is the autofocus mechanism called?

A

The near response (it is the way we change refractive power of optical components).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What happens to refractive power when the lens becomes more round?

A

refractive power increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

If we want to bring the image forward what do we need to do to refractive power?

A

Adding refractive power brings the image forward.

When you increase the refractive power of the lens, you’re essentially increasing its ability to bend light rays. This means the light rays converge more sharply, bringing the focal point closer to the lens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What shape is the lens when the ciliary muscle is relaxed?

A

Flat = shallow curvature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Is the ciliary muscle relaxed when looking at something close up or looking at something far away?

A

Far away

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is happening to the zonular fibres when the ciliary muscle is relaxed?

A

They are taut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

When gaze shifts to close up objects what happens to the parasympathetic activity and beyond that allows you to see close up object?

A

It increases the parasympathetic activity of the ciliary muscle causing it to contract.

Tension is removed from zonular fibers.

Lens becomes more spherical due to natural elasticity.

Eyes total refractive power increase from about 60 up to about 75 diopters.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What happens to the size of the pupil when you look at something close up and why?

A

Decreases in size because ciliary muscle contracts.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What are 5 optical defects?

A

Myopia
Hypermetropia
Astigmatism
Presbyopia
Cataract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What is emmetropia?

A

Normal vision - 20/20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is myopia?

A

Short sighted.

Myopia occurs when the eyeball is too long or the cornea is too steep, causing light rays to focus in front of the retina rather than directly on it. As a result, distant objects appear blurry, while close objects can be seen more clearly.

To correct myopia, concave (diverging) lenses are used. These lenses help to diverge light rays before they enter the eye, allowing them to focus correctly onto the retina. This effectively shifts the focus point back onto the retina, improving distance vision.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is hypermetropia?

A

Far sighted.

Hypermetropia occurs when the eyeball is too short or the cornea is too flat, causing light rays to focus behind the retina rather than directly on it. This results in blurry vision, particularly when looking at close objects, while distance vision may remain relatively clear.

To correct hypermetropia, convex (converging) lenses are used. These lenses converge incoming light rays before they enter the eye, allowing them to focus correctly onto the retina. This brings the focus point forward onto the retina, improving both distance and near vision.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What are optical defects?

A

Abnormalities in the shape and size of the eyeball.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is astigmatism?

A

Where the eye ball is aspherical (more of a rugby ball than a soccer ball).

The result of this is that there are different amounts of refraction in different planes (different refraction dependant on where the light comes from).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

What corrects astigmatism?

A

Cylindrical lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is presbyopia?

A

Age related loss of accommodation = caused by lens losing elasticity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What does the elasticity of the lens fall from children –> 45/50 year –> 70 year and the consequence on near point?

A

Therefore accommodation falls from about 15 diopters in children to 2 diopters at around 45-50 years and essentially 0 at 70.

recedes from 10cm at 20 years to 80cm at 60 years.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What lens is required to correct presbyopia?

A

Convex - restore near vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What is a cataract?

A

Where the lens becomes opaque due to the lens being broken up inside lens capsule.

Occurs predominately with age but some children (Alice) are born with it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

How is a cataract fixed?

A

Plastic lens - but plastic is not flexible so therefore no accommodation so require convex lens.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Where is the neural circuit of the eye?

A

Retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Where in the neural circuit are photoreceptors (light sensitive cells) located?

A

Furtherest from the light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

What are the three interneurons in the eye neural circuit?

A

Bipolar cells
Amacrine cells
Horizontal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

What are the retinal ganglion cells?

A

The only cells within eye neural circuit with axons. They send information from retina to other visual centres in the brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

What cells are pushed out in the Fovea Pitt and what is the effect of this?

A

Ganglion and interneuron cell bodies pushed out to side.

Means that photons have a more direct path to reaching photoreceptors as less intervening substances that may reflect light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

What are the proportion of Rods and Cones in eye?

A

More Rods than Cones in retina.

But less rods than cones in fovea.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

What are the two types of photoreceptors?

A

Rods
Cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Are rod or cones used for night vision?

A

Rods function in low light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Do rods or cones detect colour?

A

Cones - require relatively hight light levels - day and twilight vision.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

What are the three colours types that Cone photoreceptors detect?

A

Red, Green and Blue light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

Why do rods have bigger surface areas than cones?

A

Rod are made up of individual free floating discs whereas cones are made up of folding membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

What are photopigments?

A

Proteins that are sensitive to different wavelengths of light - I is what gives photoreceptors the capacity to response to light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

What are the two components that photopigments consist of?

A

Opsin (membrane spacing protein)

Retinal (chromophore)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

What type of opsin do rods have?

A

Rhodopsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

What type of opsin do cones have?

A

Photopsin

Either Short (Blue), Medium (Green) or Long (Red)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

What is retinal a derivative of?

A

Vitamin A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

Describe phototransduction in the dark:

A

Phototransduction in the dark is essentially the excitatory process.

The inactive retinal is in its 11-CIS isoform.

We have enzymes in the eye making lots of cyclic GMP.

cGMP gated channels open and there is a influx of cations including Na (sodium).

Positive charge coming in means that photoreceptors are a little depolarised due to the cGMP.

Depolarisation results in releasing lots of neurotransmitter glutamate onto the interneuron terminals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

Describe phototransduction in the light:

A

Phototransduction in the light is essentially the inhibitory process.

Light energy is absorbed and used to convert retinal from CIS to TRANS isomer. TRANS is the active isoform.

cGMP is broken down - this results in less cGMP and gated channels close. Therefore less Na influx, photoreceptors hyperpolarised and less glutamate released.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

What is the one thing that light does?

A

Converts retinal from CIS to TRANS form.

Everything else in the eye is all a consequence of this and not because of light itself.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

What are the only cells in the retina that fire AP?

A

Retinal ganglia cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

What is the perception of colour created by?

A

Relative activation of the three cone types of photopigments (S, M, L).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

How can you become colourblind?

A

Opsin is a protein which is a product of a gene - therefore colour blindness can be inherited. Can also be acquired due to disease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

Why are males more likely to be colour blind than females?

A

Colourblindness affects 8% of males and 0.5% of females.

This is because the gene encoding production of M and L photopsin are on the X chromosome. Therefore males only get one of them so if have it, it will be expressed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

What do electrical responses of ganglion cells depend on for retinal processing?

A

The spatial and temporal pattern of light stimulation on the retina.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

What role does receptive fields have in retinal processing?

A

The input to each ganglion cell arises from neighbouring photoreceptors in a circumscribed area of the retina = the cells receptive fields.

RF are roughly circular and divided into two parts = central and the surround.

Ganglion cells respond optimally to the differential illumination of the centre and the surround.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

What is light illumination?

A

Contrast in the light - enables us to see shapes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

What are the two types of ganglion cell receptive fields?

A

On-centre and off-centre.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

If you have an on-centre RF and light falls on the surround what happens?

A

If more light on the surround you inhibit AP.

If more light in centre then it is excited.

The opposite is true for off-centre RF.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

What is the effect of large receptive fields on acuity?

A

Low acuity (Acuity meaning 2 point discrimination).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

What is the pathway of information from the eye to the primary visual cortex?

A

Retina
Optic Chiasm
Optic Tract
Material Geniculate Nucleus
Primary Visual Cortex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

If someone is in your left visual space where do axons from each eye go?

A

If in left visual space light reflects to the nasal of left eye and temporal of right eye.

Information is brought together on the same side of the brain due to different crossing pathways at chiasm - ipsilateral (same) projection of axons from right eye and contralateral (opposite) projection from left eye.

Means that information concerning images from visual space falling on equivalent parts of the two retinas are brought together for central processing.

Axons got to the primary visual cortex at the dorsal end of the brain for first visual processing.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

What are the four subcortical visual nucleus that ganglion cell axons project to?

A

Superior Colliculus
Lateral Geniculate Nucleus
Pretectum
Suprachiasmatic Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

What is the Superior Colliculus?

A

The subcortical visual nucleus that sends information of head movement to move eyes along with it to give stable vision.

Concerned with eye movements and orientation to visual stimuli.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

What is the Lateral Geniculate Nucleus?

A

The subcortical visual nucleus concerned with the sensation of vision.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

What is the Pretectum?

A

The subcortical visual nucleus that is concerned with the control of pupils - for focus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

What is the Suprachiasmatic nucleus?

A

The subcortical visual nucleus that controls diurnal rhythms (senses daylight).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

What is sound?

A

Pressure waves in the air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

What determines the pitch of sound?

A

Frequency of pressure waves (number of cycles per second).

97
Q

What determines the loudness of sound?

A

Amplitude of pressure waves

98
Q

What is the unit of frequency?

A

Hertz

99
Q

What is volume of noise measured in?

A

Decibels (dB)

100
Q

What range of frequency are humans most sensitive to?

A

200-1000 HZ e.g., we can hear 0dB at these frequencies.

101
Q

What is the special structure that allows us to hear (what is the hearing apparatus)?

A

The ear

102
Q

What is the human threshold of hearing?

A

Around 50 Hz

103
Q

What happens to the threshold of hearing curve when someone has a hearing impairment?

A

The curve moves up - e.g., require higher dB (louder volume) to be able to hear.

104
Q

What dB is normal speech?

A

60dB

105
Q

At what dB would noise cause pain and immediate permanent hearing damage?

A

140dB

106
Q

How many components are there in the ear?

A

Three: External ear, Middle ear and Inner ear.

107
Q

Which component of the ear is not air filled?

A

Inner ear

108
Q

What is the inner ear filled with?

A

Fluid

109
Q

What are the two main components of the inner ear?

A

Cochlea and The Vestibule System.

The inner ear is a network of fluid filled tubes.

110
Q

What is “popping” of the ear drums?

A

The air pressure equalising across the tympanic membrane.

111
Q

What is the auditory apparatus of the ear?

A

Cochlea

112
Q

What are the names of the three small bones in the middle ear?

A

Malleus, incus and the stapes.
Collectively known as the ossicles.

113
Q

What is the function of the ossicles bones?

A

Delivers vibration caused by pressure waves across the middle ear cavity to stapes which is touching oval window of inner ear.

114
Q

What does the external ear consist of?

A

Pinna
External auditory canal
Tympanic membrane

115
Q

What is the pinna and why is its structure important?

A

The folded cartilage covered in skin.

Shape and depth of the pinna is important for reflecting sound waves into external auditory canal.

116
Q

What is the external auditory canal?

A

The tunnel that leads from external of head to the tympanic membrane (the ear drum).

117
Q

What are both the Scala vestibule and Scala tympani filled with?

A

Perilymph fluid

118
Q

What is the Scala Media filled with?

A

Endolymph fluid

119
Q

What is the composition of endolymph fluid?

A

Like intracellular fluid = high in potassium.

(Fluid of the Scala media)

120
Q

What is the composition of perilymph fluid?

A

Like extracellular fluid = high in sodium

(Fluid of the Scala tympani and Scala vestibuli)

121
Q

What are the three cross section compartments of the cochlea?

A

Scala Vestibule
Scala Media
Scala Tympani

122
Q

What are the three membranes in the cochlea and which compartment does each surround?

A

Scala Vestibule surrounded by Reissner membrane

Scala Media surrounded by Tectorial membrane

Scala Tympani surrounded by baslar membrane

very rarely, my teeth, turn black

123
Q

What is the Organ of Corti and where is it located?

A

A collection of cells where signal transduction of the ear occurs.

Located in the middle compartment of cochlea = scarla media.

124
Q

Does potassium or sodium cause depolarisation in the ear and why?

A

Potassium - because the Organ of Corti is located in scarla media which is filled with endolymph fluid which has a high concentration of potassium.

125
Q

What is significant about the basilar membrane?

A

The membrane has different flexibility along its length e.g., wide and floppy at one end and narrow and stiff at the other end.

The wide and flopping ends natural frequency of oscillation is lower = it oscillates in time with low frequency sounds.

The narrow and stiff ends natural frequency of oscillation is higher = it oscillates in time with high frequency sounds.

126
Q

What are the steps taken for the ear to transfer pressure waves to AP?

A

Pressure waves from the air enter external auditory canal > deflects the tympanic membrane > middle ear bones move > staples middle ear bone causes the membrane in oval window to move > basilar membrane moves at the point along it’s length that is in tune with the frequency of the pressure waves > deflection of stereocelia on overlying organ of corti (cells in scale media) > opening of mechanoreceptors > influx of K+ > Depolarisation at a location along the Basilar Membrane that corresponds to the pitch of the sound > AP to auditory cortex.

127
Q

What are stereocilia?

A

The hair cells of the ear

128
Q

What membrane of the cochlea overlies stereocilia cells?

A

Tectorial membrane

129
Q

What type of ion channels are located on the tips of steocilia?

A

Mechanically gated K+ ion channels

130
Q

What is the kinocilium?

A

The specialised single cilia at the end of every row of sterocilia - it is the longest one.

131
Q

What is happening during positive mechanical deformation?

A

Sterocilia are moving towards the kinocilium causing mechanically gated K+ channels in sterocilia to open = depolarisation.

132
Q

What is happening during negative mechanical deformation?

A

Sterocilia are moving award from the kinocilium causing mechanically gated K+ channels in sterocilia to close = hyper-polarisation.

133
Q

Is the process of signal transduction faster for hearing or vision?

A

Hearing - because sound wave directly opens ion channels itself (mechanically gated) - no secondary messengers involved.

134
Q

What are the four sound qualities we can discriminate?

A

Pitch
Intensity
Duration
Direction

135
Q

What does the frequency of sound waves determine?

A

Pitch

136
Q

What does the frequency of AP determine?

A

Loudness

137
Q

How do we discriminate the direction of sound?

A

The time difference in activation of receptors in each ear and by the intensity (loudness) difference in each ear.

138
Q

What are the four central auditory pathways?

A

1) Auditory receptors in cochlea
2) Brain stem neuron’s
3) Medial Geniculate Nucleus
4) Auditory cortex (each side receives information for both ears)

139
Q

What is deafness?

A

A raised threshold to sound stimuli

140
Q

What are the two types of deafness?

A

Conduction Deafness
Sensorineural Deafness

141
Q

What is conduction deafness?

A

Impair sound transmission through out or middle ear due to blockage or infection.

Can be generated by yourself by sticking fingers in ears which blocks sound waves.

142
Q

What is sensorineural deafness?

A

Damage to receptors or neural pathways - can be due to exposure to loud noises, some antibiotics, tumour or meningitis.

Arises due to damage to auditory apparatus.

143
Q

What does exposure to loudness damage that leads to deafness?

A

Hair cells

144
Q

Can damage to hair cells be repaired?

A

No - once you loose them they don’t grow back.

145
Q

What is the importance of the vestibular system?

A

The sensory system that creates the sense of balance and spatial orientation for the purpose of coordinating movement with balance e.g., it mediate our sense of balance and gives the brain information about what the head is doing.

Keeps image of the world on the retina stable.

146
Q

Where is the vestibular system?

A

The other part of the inner ear - that is not the cochlea.

147
Q

What does the vestibular system report?

A

Acceleration (change in velocity).

148
Q

What are the two types of acceleration that the vestibular system reports?

A

Linear
Angular (rotational)

149
Q

What is the stimulus for the vestibular system?

A

Change in head position (typically reliant on gravity).

150
Q

Why can we not rely on visual signalling for balance?

A

Because visual transduction is slow due to secondary messenger system.

Whereas, vestibular transduction is fast as does not rely on secondary messengers.

151
Q

What are the components of the vestibular system?

A

Otolith organs for linear acceleration reporting.

Semicircular canals for rotational acceleration reporting.

152
Q

How many semicircular canals do we have in total?

A

6 (three in each ear).

153
Q

What type of fluid is the semicircular canals filled with?

A

Endolymph

154
Q

What is the swelling at the based of each semicircular canal called?

A

Ampulla

155
Q

Where in the ampulla do hair cells sit?

A

Cupula

156
Q

What part of the vestibular reports on linear acceleration?

A

Otolith organs (saccule and utricle)

157
Q

What is the hair cell membrane of the ampulla called?

A

Crista ampullaris

158
Q

During acceleration what does the movement of enclosed endolymph cause?

A

Pushed against the cupula which displaces the hairs on the hair cells causing the opening of mechanical gated ion channels = influx of K+.

159
Q

At rest are AP firing from vestibular hair cells?

A

Yes - they have a resting rate of discharge meaning that they can signal in two directors (increase or decrease - if at rest was 0 then wouldn’t be able to decrease).

160
Q

What direction do the hair cells go to cause an increase in the frequency of AP?

A

Towards the longest hair cell (towards the kino)

161
Q

Does the Utricle or Saccule report on vertical linear acceleration?

A

Utricle = horizontal

Saccule = vertical

162
Q

What makes otolith organs top heavy?

A

Otoconia - stones of calcium carbonate located onto of fluid.

163
Q

What is information from vestibular system used for in the brainstem and how?

A

stabilise eyes - through oculomotor nuclei

stabiles the head - via input from neck muscle motoneurons

maintain balance - via pathways to cerebellum and spinal cord

164
Q

What are the three vestibular disorders?

A

Vertigo
Motion Sickness
Bedspins

165
Q

What is vertigo caused by and its symptoms?

A

Caused by diseases affecting the vestibule or its afferent fibres.

Causes illusion of movement, dizziness, nausea.

166
Q

What is motion sickness caused by?

A

Caused by mismatch between visual and vestibular information.

167
Q

What helps motion sickness?

A

If the horizon is visible

168
Q

What causes ‘bed-spins’?

A

Caused by alcohol - the ethanol infiltrates the cupula, lowers elasticity and causes it to float creating perception of movement when your not actually moving.

169
Q

What are Ototoxic drugs?

A

Drugs that are known to be harmful to hair cells = can result in temporary or permanent hearing loss and disorders of balance.

170
Q

What type of antibiotics are amongst the worst ototoxic drugs?

A

Aminoglycoside antibiotics e.g., gentamicin, streptomycin and kanamycin.

171
Q

What helps reduce the effects of ototoxic drugs?

A

Vestibular rehabilitation

172
Q

What is the Cupula?

A

A gelatinous matrix

173
Q

What causes mechanically gated ion channels of the semicircular canals to open?

A

During rotational acceleration the enclosed endolymph (due to cupula blocking) pushes on the cupula which displaces the hair cells that sit within it. The displacement of hair cells opens mechanically gated ion channels and causes depolarisation.

174
Q

Are sterocilia more active on the left or the right if the head turns to the left?

A

Left

175
Q

What direction does endolymph in the ampulla move if the head accelerates to the left?

A

right - endolymph moves in opposite direction to head acceleration in the ampulla.

176
Q

What do vestibule-ocular reflexes do?

A

Promote stable images on the retina during head movements - Nystagmus is a type of vestibule-ocular reflex.

177
Q

Is the semicircular canal in the same plane as acceleration the only canal stimulated?

A

No - it is just most stimulated by acceleration in its preferred plane.

178
Q

What type of receptors are used to sense taste and smell?

A

Chemoreceptors

179
Q

What are 5 purposes of having chemical sense (taste and smell)?

A

Sample the content of food/drunk for nutrient content, palatability and toxicity.

Generate sensory perceptions in response to ingested and inhaled chemicals.

Guide appetite, trigger processes for absorbing nutrients.

Avoid poisons and chemical hazards.

Find a mate.

180
Q

What percent of odours are ‘pleasant’?

A

20%

181
Q

Where are taste buds located?

A

Within tongue papillae - on upper surface of the tongue.

182
Q

What are the three types of tongue papillae?

A

Foliate - outside edge
Circumvallate - back of tongue
Fungiform - front/around outside

183
Q

What type of cells are taste bud cells?

A

Columnar epithelial cells (come in clusters)

184
Q

What type of cells do taste buds sit within?

A

Epithelia cells

185
Q

Where else other than the tongue are taste buds located?

A

Palate
Pharynx
Epiglottis

186
Q

What is the turned over half life of sensory cells?

A

10-14 days

187
Q

What are the three types of cells found in each taste bud?

A

Type 1 (support)
Type 2 (chemoreceptors = GPCR)
Type 3 (ion channels)

188
Q

What is the role of Type 1 taste bud cells?

A

They are essentially support cells (glial like role) - they mop up transmitters and K+.

Are not directly involved in taste sensation.

189
Q

What type of receptor do Type 2 taste bud cells have?

A

GPCR chemoreceptors

190
Q

What are the 5 detectable classes of taste?

A

Sweet
Sour
Salt
Bitter
Umani (amino acids)

191
Q

How does signal transduction occur in Type 3 taste bud cells?

A

through ion channels

192
Q

What is sweet taste stimulated by?

A

Sugars

193
Q

What is sour taste stimulated by?

A

Acids (esp organic acids like citric and acidic acids)

194
Q

What is salty taste stimulated by?

A

Sodium (NaCl)

195
Q

What is bitter taste stimulated by?

A

Typically alkaloids (but complex)

196
Q

What is umani taste stimulated by?

A

Amino acids esp glutamate

197
Q

What molecules/neurotransmitters are involved in taste signalling in taste buds?

A

ATP
GABA
Serotonin
ACh

198
Q

What is different about type 2 receptor cell mechanism to sensing taste?

A

In cases of type 2 receptor cells - release of signalling molecule is via a non-vesicular mechanism (does not involve the formation or transport of vesicles - instead relies on other mechanisms of transport).

199
Q

What tastes are type 2 taste bud cells receptive to?

A

Sweet, Umani, and Bitter

200
Q

Is insulin released before or after blood sugar rises?

A

Before

201
Q

As well as indicating sweet substances in the mouth what else does T1R (homodimeric GPCR) activation initiate?

A

Cephalic Phase Insulin Release

202
Q

What is the name of the G protein complex that is activated by T1R?

A

Gustducin

203
Q

What does gustducin activate?

A

PLC

204
Q

What does PLC activation result in?

A

Release of Ca2+ from the ER –> depolarisation (via TRPM5) –> release of signalling molecule via atypical non-vesicular mechanism.

205
Q

What type of channel is the TRPM5?

A

Temperature sensitive (why ice cream tastes sweet when it is warmer because results in bigger release of neurotransmitters thought channel and therefore bigger response).

206
Q

What does binding of sweet to sweet receptor cause an increase in?

A

IP3

207
Q

What is the umani taste?

A

“savoury, delicious”

208
Q

What is umami sensed by and stimulated by?

A

Sensed by Type 2 cells, stimulated by amino acids, esp glutamate and asparate

209
Q

What type of T1R is umami detected by?

A

T1R subtype GPCR heterodimers

210
Q

What does umami promote?

A

Eating behaviour to ensure uptake of essential amino acids

211
Q

What type of GPCR are involved in bitter taste?

A

Monomeric GPCR

212
Q

What results in depolarisation for sour taste?

A

Accumulation of protons via Otop 1 > reduces pH and blocks the leaky K+ channels which normally keep cells at RMP. Therefore, results in depolarisation and the influx of Ca2+ results in release of neurotransmitter.

213
Q

Does salty taste use a G-protein signalling pathway?

A

No

214
Q

How does Na+ enter cells?

A

Through ENaC - epithelial Na channel

215
Q

What drug blocks the epithelial Na channels?

A

Amiloride

216
Q

What makes other ‘tastes’ such as spiciness not true tastes?

A

Because the stimulating chemicals do not interact with specific oral taste receptors

217
Q

What senses spiciness?

A

heat and pain sensitive nerve fibres in the mouth that are stimulated by chemical such as capsaicin and piperine

218
Q

What is capsaicin?

A

An active component of chili peppers - plants from the genus capsicum

219
Q

What is piperine?

A

The alkaloid that gives pepper its pungency

220
Q

What nerves innervate anterior tongue taste buds?

A

Chorda tympani

221
Q

What nerves innervate posterior tongue taste buds?

A

Glossopharyngeal

222
Q

Where do afferent fibres of central taste pathways synapse?

A

Medulla

223
Q

Is most gustatory input to the brain crossed or uncrossed?

A

Uncrossed

224
Q

What does hypolglossal mean and how does it relate to the tongue?

A

Hypolglossal means the area below the tongue - location where the main motor nerve supply of the tongue goes.

225
Q

Where is the taste cortex (gustatory cortex)?

A

below parental lob and behind somatosensory cortex (nearest to bottom of cortex map that has lips/tongue etc)

226
Q

What are odorant’s inhaled and swirled around by?

A

Nasal conchae

227
Q

What do ordorants dissolve in?

A

Water mucus in the roof of the nasal cavity - e.g., snot. Then binds to receptors within it.

228
Q

What projects from olfactory receptors?

A

Non-motile cilia

229
Q

Do olfactory hair cells move?

A

No - they are non motile.

230
Q

What do odourants interact with?

A

Receptors (GPCR) on the olfactory cell membrane

231
Q

Once olfactory GPCR are activated what happens?

A

There is an increase in cAMP which causes the opening of cation channel and cation entry causing depolarisation.

This causes the opening of voltage gated Cl- channels and Cl- to go out of the cell increasing depolarisation.

This carries the AP to olfactory bulb.

232
Q

What is are olfactory cells?

A

Neurons

233
Q

Where are olfactory bulbs?

A

Underside of frontal lobes

234
Q

What do olfactory axons form?

A

The first cranial nerve

235
Q

Where do olfactory bulb axons pass to?

A

Olfactory cortex in limbic system - the part of our brain associated with emotion, food-getting and sexual behaviour.

236
Q

What is flavour the sum of?

A

Input from 5 taste cells
Input from odour receptors
Product temperature
Product texture
Spiciness (pain)
Also influence by appearance

237
Q

Can one odorant activate more than one receptor type?

A

Yes - the combination of activated receptors is interpreted in the brain to give the quality of the odour.

238
Q

What are the three nerves in the central pathway that taste buds can innervate?

A

Chorda tympani nerve (anterior taste buds)
Glossopharyngeal nerve (posterior taste buds)
Vagus Nerve (some)