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BioMed S2 > 18. Sense Organs > Flashcards

18. Sense Organs Flashcards

1
Q

Which cranial nerve supplies the ear?

A

Vestibulocochlear (8th)

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2
Q

What are the sections of the ear?

A

Outer ear
Middle ear
Inner ear

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3
Q

How is the middle ear connected to the nasopharynx?

A

Eustachian tube

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4
Q

What does the outer ear consist of?

A

Auricle/pinna
External auditory canal
Tympanic membrane (ear drum)

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5
Q

What is the auricle/pinna?

A

Flap of elastic cartilage
Covered by skin

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6
Q

What is the function of the pinna?

A

Traps and directs sounds waves into the external auditory canal

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7
Q

What is the tympanic membrane?

A

Ear drum
Thin semi-transparent partition between the external auditory canal and middle ear

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8
Q

What is the tympanic membrane lined with?

A

Simple cuboidal epithelium
Elastic fibres
Collagen fibres

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9
Q

What is the function of the tympanic membrane?

A

Transmits sound from the outer ear to the auditory ossicles
Converts sound waves into mechanical vibration

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10
Q

What is the middle ear?

A

A small air-filled cavity in the temporal bone

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11
Q

What does the middle ear consist of?

A

Malleus (hammer)
Incus (anvil)
Stapes (stirrup)

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12
Q

What is the function of the middle ear?

A

Transmits sound in the form of vibration from the tympanic membrane to the inner ear (cochlea)

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13
Q

What does the stapes connect to?

A

Oval window

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14
Q

What does the oval window connect to?

A

Cochlea

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15
Q

What is the stapedius?

A

Small muscle that dampens large vibrations
Innervated by the facial nerve

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16
Q

What is the alternative name for the inner ear?

A

Labyrinth

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17
Q

What does the labyrinth consist of?

A

Bony labyrinth (outer)
Membranous labyrinth (inner)

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18
Q

What does the bony labyrinth consist of?

A

Series of cavities in the temporal bone:
Three semi-circular canals
Vestibule
Cochlea

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19
Q

What do the semi-circular canals and vestibule help with?

A

Balance

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20
Q

What does the cochlea help with?

A

Hearing

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21
Q

Which fluids does the labyrinth contain?

A

Perilymph
Endolymph

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22
Q

What is the cochlea?

A

Spiralled, hollowed chamber
Almost 3 turns around a central bony core

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23
Q

What does the cochlea contain?

A

Epithelial cells lined with hair cells

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24
Q

What are the hair cells in the cochlea called?

A

Stereocilia

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25
Q

What is the function of the stereocilia?

A

Hearing receptors that extend into the endolymph

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26
Q

How does the structure of the cochlea aid hearing?

A

Movement of the endolymph causes stereocilia movement
This initiates an electrical impulse

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27
Q

What does the vestibulocochlear nerve do?

A

Provides sensory information for hearing and balance

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28
Q

What are the two parts of the vestibulocochlear nerve?

A

Vestibular branch/fibres
Cochlear branch/fibres

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29
Q

What do the vestibular fibres consist of?

A

Nerve branches that synapse with receptors for balance

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30
Q

What do the cochlea nerve fibres do?

A

Provides hearing

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31
Q

Where does the vestibulocochlear nerve terminate?

A

Brainstem (pons/medulla oblongata)

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32
Q

How can the vestibulocochlear nerve get damaged?

A

Basilar skull fracture
Affecting both hearing and balance

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33
Q

How does the outer ear make sound?

A
  1. Sound comes in
  2. Pinna concentrates the soundwaves and directs them along the external auditory canal
  3. This causes the tympanic membrane to vibrate
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34
Q

How does the middle ear make sound?

A
  1. Vibrations from the tympanic membrane are transmitted through the middle ear by movement of the three auditory ossicles (malleus, incus, stapes)
  2. The footplate of the stapes rocks at the oval window sending fluid waves into the cochlea perilymph
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35
Q

How does the inner ear make sound?

A
  1. Pressure waves are transmitted into the cochlea which causes the round window to bulge into the middle ear
  2. This pressure wave is transmitted into the endolymph and vibrates the basilar membrane and stereocilia
  3. The bending of the stereocilia creates a receptor potential - generating an action potential to the nerves
  4. The nerve impulses move along the vestibulocochlear nerve to the hearing area in the cerebrum
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36
Q

What are the properties of sound?

A

Pitch
Volume

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37
Q

What is pitch?

A

Frequency of sound waves

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38
Q

How is pitch measured?

A

Hertz (Hz)

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39
Q

What is volume?

A

Amplitude of sound waves

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40
Q

How is volume measured?

A

Decibels (dB)

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41
Q

What is the decibel scale?

A

0 dB - near silence
10 dB - 10x more powerful
20 dB - 100x more powerful
30 dB - 1000x more powerful

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42
Q

What is a whisper in decibels?

A

15 dB

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43
Q

What is a normal conversation in decibels?

A

60 dB

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44
Q

What is a lawnmower in decibels?

A

90 dB

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45
Q

What is a car horn in decibels?

A

110 dB

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46
Q

What is a rock concert/jet engine in decibels?

A

120 dB

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47
Q

What is a gunshot in decibels?

A

140 dB

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48
Q

What decibel level can cause hearing loss?

A

85 dB

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49
Q

What decibel level can cause pain/damage?

A

140 dB

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50
Q

What is white noise?

A

A constant, background noise that contains all the different frequencies of sound
Brain ignores

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51
Q

What is white noise used for?

A

To block out other sounds
Aid concentration

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52
Q

What is the function of the eustachian tube?

A

Opens for air to equalise pressure between middle ear and atmosphere
Drains mucus

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53
Q

What can make the eustachian tube open?

A

Yawning
Swallowing

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54
Q

Why is it essential that air can escape the middle ear?

A

Damage could occur with pressure changes

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55
Q

What is common in children as a result of the eustachian tube being horizontal?

A

Infection between middle ear and pharynx

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56
Q

What do the semi-circular canals and vestibule provide information about?

A

Head position

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57
Q

What do the semi-circular canals and vestibule contain?

A

Stereocilia

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58
Q

What extends and rests on the stereocilia?

A

Dense layer of calcium carbonate crystals

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59
Q

What is the layer of calcium carbonate crystals also known as?

A

Otolithic membrane

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60
Q

What does a change in head position create?

A

Movement in the perilymph and endolymph that causes stereocilia to bend

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61
Q

What does bending of the stereocilia in the semi-circular canals and vestibule stimulate?

A

Stimulates the sensory nerve endings, creating action potential via CN8

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62
Q

Where does the action potential stimulated in the semi-circular canals and vestibule transmit to?

A

Cerebellum

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63
Q

Where does the cerebellum get information from to help with balance?

A

Vestibular feedback (from inner ear)
Visual feedback (from eyes)
Proprioceptors (skeletal muscles, joints, ligaments)

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64
Q

How does the cerebellum maintain balance?

A

Co-ordinates:
Vestibular feedback (from inner ear)
Visual feedback (from eyes)
Proprioceptors (skeletal muscles, joints, ligaments)
and passes efferent impulses to the cerebrum and skeletal muscles

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65
Q

Where is the eye located?

A

In the orbital cavity

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66
Q

Which cranial nerve serves the eye?

A

Optic nerve (CN II)

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67
Q

What are the layers of the eye?

A

Sclera & cornea (outer)
Uvea (middle)
Retina (inner)

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68
Q

What does the uvea consist of?

A

Iris
Ciliary body (muscle)
Choroid (rest of the layer)

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69
Q

What is the iris?

A

Coloured part of the eye
Controls the amount of light reaching the retina by adjusting pupil size

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70
Q

Where is the lens located?

A

Behind the pupil

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71
Q

What does the lens do?

A

Focuses light along with the cornea

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72
Q

What are the accessory structures of the eye?

A 
Eyebrows
Eyelids
Eyelashes
Conjunctiva
Lacrimal apparatus
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73
Q

What function do the eyebrows play?

A

Prevents sweat/materials entering the eye

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74
Q

What function do the eyelids play?

A

Spread secretions over the eye
Protection

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75
Q

What is the conjunctiva?

A

Transparent mucus membrane of columnar epithelial cells lining the internal eyelids and anterior eyeball

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76
Q

What is the function of the conjunctiva?

A

Protects the cornea

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77
Q

What does the lacrimal apparatus do?

A

Produces tears

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78
Q

What does blinking do?

A

Spreads tears
Protects the eyes from injury (when eyelids are closed)

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79
Q

What function do tears have?

A

Protect the eye from infection
Lubricate eye movement
Emotions

80
Q

Which cranial nerve controls the secretion of tears?

A

Trigeminal nerve (CN V)

81
Q

What do tears contain?

A

IgA
Lysozymes

82
Q

Where are tears produced from?

A

Lacrimal gland

83
Q

How do tears cover the eye?

A

Through blinking

84
Q

What is the lacrimal punctum?

A

Where tears run in to before entering the nose

85
Q

How do tears enter the nose?

A

Via the nasolacrimal gland

86
Q

What are eyes responsible for?

A

Detecting visible light

87
Q

What is visible light?

A

Part of the electromagnetic spectrum
Wavelengths between 400-700nm
Exhibits colour depending on wavelength

88
Q

How does light affect the colour of objects ?

A

The appearance of colour is the wavelength reflected by the object

89
Q

What is white light?

A

Combination of all the colours of the visible spectrum

90
Q

How is clear vision achieved?

A

By light focusing on the retina

91
Q

How does light focus on the retina?

A

Refraction of light rays
Accommodation of the eyes
Changing the size of the pupils

92
Q

What is refraction?

A

Bending of light rays

93
Q

How does refraction happen?

A

When light moves from one substance to another which has a different density

94
Q

How do the cornea and lens help with refraction?

A

They both refract light rays and help focus the image on the retina

95
Q

How do images appear to the retina?

A

Inverted (upside down)
Left-right reversed

96
Q

What happens when objects are closer than 6m?

A

Light rays are refracted more to enable the retina to focus

97
Q

What is the process of refracting more light rays called?

A

Accommodation

98
Q

What happens during accommodation?

A

Lens curvature becomes greater, the focusing power increases

99
Q

What are the characteristics of the lens?

A

Convex on anterior and posterior surfaces
Allows refraction of incoming light

100
Q

What do the lens and ciliary muscles do to project a sharp image on the retina?

A

Lens changes its refractive power:

  1. Close objects - ciliary muscle contracts
  2. Distant objects - ciliary muscle relaxes
101
Q

What happens when the ciliary muscle contracts?

A

Reduces the suspensory ligament tension
Lens becomes more convex = greater refraction

102
Q

What happens when the ciliary muscle relaxes?

A

Lens becomes flattened = less refraction
Increases the suspensory ligament tension

103
Q

What does looking at near objects constantly do to the eyes?

A

Tires them out

104
Q

What happens to pupil size during sympathetic nervous stimulation?

A

Radial muscles contract = dilation of pupils

105
Q

What happens to pupil size during parasympathetic nervous stimulation?

A

Circular muscles contract = constriction of pupils

106
Q

What is meant by convergence?

A

The medial movement of two eyeballs so that both are directed towards an object

107
Q

Which muscles move the eyes during convergence?

A

Extra-ocular

108
Q

What happens to eye rotation if an object is near?

A

More rotation

109
Q

What happens if convergence isn’t completed?

A

Two images are sent to the brain
Leads to double vision - diplopia

110
Q

What does focusing on one object allow for?

A

Perception of depth

3D

111
Q

What happens in binocular vision?

A

Two images from the two eyes are fused in the cerebrum so only one image is perceived

112
Q

What is optic chiasma?

A

Where the optic nerve crosses over in the brain

113
Q

Where is the optic chiasma located?

A

Next to the pituitary gland

114
Q

What condition can pituitary tumours cause?

A

Tunnel vision

115
Q

What is the retina?

A

Inner layer of the eye
Beginning of the visual pathway
Lines the posterior 3/4 of the eyeball

116
Q

How can the retina be viewed?

A

Through an ophthalmoscope

117
Q

What can be viewed in the retina?

A

Blood vessels
Optic nerve

118
Q

What is the optic disc?

A

Location where the optic nerve exits the eyeball

119
Q

What is the location where the optic nerve exits the eyeball also called?

A

Blind spot

120
Q

What is the optic nerve bundled with?

A

Central retinal artery and vein

121
Q

What does the retina contain?

A

Pigmented layer of melanin-containing epithelial cells
Layer of photoreceptors

122
Q

What are the photoreceptors called?

A

Rod cells
Cone cells

123
Q

How many rod cells are in the eye?

A

120 million

124
Q

What is the function of rod cells?

A

Allows us to see in dim light
Provides black, white and greyscale

125
Q

How many cone cells are in the eye?

126
Q

What is the function of cone cells?

A

Produce colour vision

127
Q

What are the types of cone cells?

A

Blue
Red
Green

128
Q

One of the reasons the optic disc is called the blind spot

A

Contains no rod or cone cells

129
Q

What is the macula lutea?

A

Yellowish spot at the exact centre of the retina

130
Q

What is the fovea centralis?

A

Small depression in the centre of the macula lutea that only contains cone cells
Area of highest visual acuity

131
Q

Where are rod cells more plentiful?

A

Periphery of the retina

132
Q

What do rod and cone cells form?

A

Invaginations of their cell membrane to create stacks of discs

133
Q

What are photopigments?

A

Transmembrane proteins within the discs of rod and cone cells

134
Q

What happens when light hits the photopigment?

A

It changes shape initiating an action potential

135
Q

What are photopigments derived from?

136
Q

What happens once a photopigment is activated?

A

It must then be restored/regenerated

137
Q

What contributes to the regeneration of rod cells?

138
Q

What are derivatives of vit A called?

139
Q

What do retinoids include?

A

Retinol
Retinal
Retinoic acid

140
Q

What does retinal do in the retina?

A

Binds to a protein called opsin to produce photopigments

141
Q

Which foods contain preformed vit A

A

Foods of animal origin
Liver
Egg yolks

142
Q

What are carotenoids?

A

Vit A precursors
Powerful antioxidants

143
Q

What are carotenoids turned into?

144
Q

Where are carotenoids metabolised into retinol?

A

Intestines

145
Q

Which foods contain carotenoids?

A 
Carrots
Sweet potatoes
Squash
Mango
Leafy greens
146
Q

How are carotenoids different to preformed vit A?

A

Not toxic
Absorption is regulated

147
Q

What happens during light/dark adaptation?

A

Dark to light = eyes adjust quite quickly
Light to dark = eyes adjust more slowly

148
Q

Why does light/dark adaptation differ?

A

Rods and cones must regenerate photopigments
Cones regenerate within 8 mins
Rods take much longer

149
Q

What is the sense of smell called?

150
Q

How many receptors does the nose contain?

A

10-100 million

151
Q

Where can the nasal receptors be found?

A

Olfactory epithelium

152
Q

What does the olfactory epithelium contain?

A

Olfactory receptors
Supporting cells
Basal cells

153
Q

What are olfactory receptors?

A

Neurons attached to olfactory hairs

154
Q

How do olfactory receptors produce an action potential?

A

By responding to chemical stimulus of odorants

155
Q

What is the function of supporting cells?

A

Physical support
Nourishment
Detoxify odorant chemicals

156
Q

What are basal cells?

A

Stem cells that continually divide to produce new olfactory receptors

157
Q

How long do olfactory receptors live for?

158
Q

Why are taste and smell ‘chemical senses’?

A

They arise from interaction with molecules

159
Q

Where can the olfactory glands be found?

A

In the connective tissue supporting the olfactory epithelium

160
Q

What do the olfactory glands do?

A

Produce mucus that is carried to the surface by ducts

161
Q

What does the mucus secreted by the olfactory glands do?

A

Moistens the olfactory epithelium
Helps to dissolve odorants

162
Q

What is affected if the nasal mucosa becomes inflamed?

A

Olfaction is inhibited

163
Q

Which cranial nerve is involved in the sense of smell?

A

Olfactory (CN I)
Unmylinated

164
Q

Where do olfactory nerves extend through?

A

About 20 olfactory foramina in the cribriform plate of the ethmoid bone

165
Q

Where do the olfactory nerves terminate?

A

Olfactory bulb - olfactory tract - olfactory area in temporal lobe

166
Q

Where do some of the axons in the olfactory tract project in to?

A

Limbic system
Hence relation between smell and emotion

167
Q

What can a sense of smell also affect?

A

Appetite
Mood

168
Q

Why does olfaction have a low threshold?

A

Only a few molecules are needed for us to detect a smell

169
Q

How do we adapt our sensitivity to odours?

A

Rapidly decreating sensitivity to odour
By 50% in first second
80% less powerful after a few mins of exposure

170
Q

When can olfaction adaptation reach 100%?

A

When constantly been exposed to an odour

171
Q

Why do we have olfaction adaptation?

A

To protect us from danger
If the scent isn’t dangerous, olfaction recalibrates to be able to detect other smells which may be harmful

172
Q

What is taste also known as?

173
Q

How do we taste?

A

Food chemicals dissolve in saliva, stimulating chemoreceptors
They encounter gustatory hairs which generates an action potential

174
Q

How many muscles are in the tongue?

175
Q

Which cranial nerve innervates the tongue?

A

Hypoglossal (CN XII)
Sensory and Motor

176
Q

How many taste buds can be found in an adult’s mouth?

177
Q

Where can the taste buds be found?

A

Tongue
Soft palate
Pharynx
Epiglottis

178
Q

What do taste buds contain?

A

Gustatory receptor cells
Supporting cells
Basal cells

179
Q

What is the function of the gustatory receptor cells?

A

Detect taste

180
Q

How long do gustatory receptor cells live for?

181
Q

What do the basal cells do?

A

Produce new gustatory receptor cells

182
Q

Where can taste buds on the tongue be found?

A

In elevations called papillae

183
Q

What are the three types of papillae?

A

Circumvallate papillae
Fungiform papillae
Foliate papillae

184
Q

What are circumvallate papillae?

A

Largest papillae
V-shaped
Found at back of tongue

185
Q

What are fungiform papillae?

A

Mushroom-shaped
Present all over tongue
Contain about 5 taste buds each

186
Q

Where can foliate papillae be found?

A

Small trenches at lateral margins of tongue
Most degenerate in childhood

187
Q

What are filiform papillae?

A

Tactile receptors that help the tongue move food

188
Q

What are the 5 tastes we can detect?

A

Sour
Sweet
Bitter
Salty
Umami

189
Q

When is taste impaired?

A

When the mouth is dry
No saliva to dissolve the tastants

190
Q

What does a sense of taste trigger?

A

Salivation
Gastric juice secretion (in preparation)

191
Q

Which cranial nerve innervates taste in the anterior 2/3 of the tongue?

A

Facial (CN VII)

192
Q

Which cranial nerve innervates taste and sensation in the posterior 1/3 of the tongue?

A

Glossopharyngeal (CN IX)

193
Q

Which cranial nerve supplies general sensation to the anterior 2/3 of the tongue?

A

Trigeminal (CN V)

194
Q

Which cranial nerve innervates the throat and epiglottis?

A

Vague nerve (CN X)

195
Q

Where does all the taste and sensory information go?

A

To the gustatory nucleus in the medulla oblongata
Some fibres to the limbic system

BioMed S2 (34 decks)

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