Special Senses Flashcards

1
Q

What are the chemical senses?

A

Olfaction

Gustation

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2
Q

Olfactory epithelium

A

5 cm squared; 10-100 million receptors

Covers superior nasal cavity and cribiform plate

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3
Q

What type of cells are contained within the olfactory epithelium?

A

Olfactory receptor
Support
Basal
Bowman’s (olfactory) glands

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4
Q

Olfactory receptor

A

AKA 1st order neuron in olfaction AKA Cranial Nerve I (Olfactory Nerve)

Bipolar neuron
Has olfactory hairs/cilia that project from dendrites

Produces generator potential (not receptor potentila)

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5
Q

Olfactory Supporting cells

A

Columnar epithelial cells

Provide physical support, nourishment, insulation to receptor cells

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6
Q

Basal olfactory cells

A

Stem cells

Produce new receptors or supporting cells

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7
Q

Bowman’s Glands

A

Produce nasal mucous

In the nasal epithelium

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8
Q

What cranial nerve innervates nasal glands and epithelium?

A

CN VII Facial

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9
Q

Olfactory transduction

A

Odorant binds to receptor protein on an olfactory cilia

Receptor protein is coupled to G protein, which activates Adenylate cyclase

Which produces cAMP

Which open Na+ channels, causing depolarization

Generator potential generated, impulse propogated

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10
Q

Olfactory adaptation

A

Initially very fast (50% in first second), then slower

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11
Q

Cribiform plate

A

In ethmoid bone

Contains 20 foramina (per nostril) to allow passage of olfactory nerves

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12
Q

Olfaction: Pathway

A

Odorants bind to receptor cilia
Generator potential –> action potential propagates along Olfactory Nerve

Pass through cribiform plate

Enter Olfactory Bulb

Synapse in Glomerulus with Mitral nerve

Mitral axons combine to form olfactory tract, which heads to the Primary Olfactory area (34). Then on to orbitofrontal area (11)
(Olfactory tract axons also project to limbic system and hypothalamus)

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13
Q

Location of olfactory bulb

A

Just below frontal lobes
Lateral to crista galli of ethmoid\

Acts as a filter

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14
Q

Location of Primary Olfactory area

A

Brodmans 34

Inferior-medial temporal lobe

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15
Q

Lateral- and auto- inhibition

A

Between excitatory mitral neurons and the inhibitory granule cells that form dendrodentritic synapses in between them.

Bidirectionality means that mitral cells can inhibit themselves and their neighbours

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16
Q

Periglomerular cells

A

Interneurons which synapse within and between glomeruli

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17
Q

Anosmia

A

Absence of smell

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18
Q

Hyposmia

A

Reduced sense of smell

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19
Q

Dysosmia

A

Distortion of sense of smell

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20
Q

Cacosmia

A

Form of dysosmia, in which things smell baaa-aad

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21
Q

Parosmia

A

Sensation of smell in the absence of appropriate stimuli

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22
Q

Phantosmia

A

Olfactory hallucination

Uncinate fits

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23
Q

Sweet

A

Activated by sugars, alcohol and some amino acids.

Measured by sucrose

Indicates energy rich foods

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24
Q

Salty

A

Activated by metal ions (especially Na+)

Measure by Na+

Indicates electrolyte-rich foods

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25
Q

Sour

A

Activated by H+ ions (acids)

Measured by HCl

Aversive

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26
Q

Bitter

A

Lowest threshold receptor

Activated by alkaloids (caffeine, nicotine)

Measured by quinine

Aversive

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27
Q

Umami

A

Activated by glutamate and aspartate

Indicate foods high in amino acids.

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28
Q

Where are taste buds found?

A

Tongue
Soft palate
Epiglottis
Pharynx

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29
Q

Papillae

A

Elevations on tongue.

Circumvallate, fungiform and folate contain taste buds.

Filiform contain tactile receptors.

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30
Q

(Circum)vallate papillae

A

12 found on posterior tongue (inverted V).

Contain 100-300 taste buds each

Innervated by glossopharyngeal nerve (IX)

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31
Q

Fungiform papillae

A

Mushroom shaped
All over tongue
Contain 5 taste buds each.

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32
Q

Folate papillae

A

On lateral tongue. Usually disappear by the end of childhood

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33
Q

Filiform papillae

A

All over tongue.

Contain tactile receptors (texture) but no taste buds.

Help move food

Trigeminal nerve (V).

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34
Q

5 basic taste receptors

A
  1. sweet
  2. salty
  3. sour
  4. bitter
  5. umami
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35
Q

How many taste buds?

A

Around 10000

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36
Q

Three type of cells in a taste bud

A

Gustatory receptor
Supporting cells
Basal cells

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37
Q

How frequently are new gustatory cells produced?

A

10 days (olfaction about 30 days)

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38
Q

What nerve is responsible for taste in the anterior 2/3 of the tongue?

A

Facial nerve (VII)

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39
Q

What nerve is responsible for taste in the posterior 1/3 of the tongue, including vallate papillae?

A

Glossopharyngeal (IX)

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40
Q

What nerve is responsible for taste in the palate and epiglottis?

A

Vagus (X)

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41
Q

What nerve is responsible for the sensation of texture when chewing?

A

Trigeminal (V)

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42
Q

How many gustatory receptors per taste bud?

A

About 50

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43
Q

How do the various tastands generate receptor potentials?

A

Salty: Na+ enters via Na+ channel.

Sour: H+ enters via H+ channel. Slows K+ leakage.

Bitter/sweet/umami: bind with receptor on membrane, activate G protein, activate secondary messenger.

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44
Q

What NT is released by the gustatory receptor cells?

A

ATP

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45
Q

Gustatory pathway

A

Gustatory receptor

First order neuron (CN VII, IX or X)

Synapse in Gustatory Nuclei (brain stem).

Second order neuron –> Thalamus
(Others go to hypothalamus/Limbic system)

Third order neuron –> primary gustatory area (43)

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46
Q

Gustatory adaptation

A

Quick (1-2 min)

Involves gustatory receptors, olfactory receptors, CNS pathways

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47
Q

How many sensory receptors are in the eye?

A

More than half

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48
Q

How much of the eyeball is in the orbit?

A

7/8

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49
Q

Palpabrae

A

Eyelids

Protect and lubricate, provide shade

Epidermis
Dermis
Tarsal plate
Tarsal glands 
Conjunctiva
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50
Q

Conjunctiva

A

Mucous membrane that lines inner eyelid and covers sclera

Stops at edge of cornea

Bulbar and palpabrael

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51
Q

Tarsal plate

A

Part of Palpabrae

Provides structural support

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52
Q

Tarsal glands

A

In tarsal plate of Palpabrae

Secrete meibom (prevents eyelids from sticking together)

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53
Q

Three regions of the ear

A

Outer ear
Middle eat
Inner ear

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54
Q

Outer ear consists of

A

Auricle
External auditory canal
Eardrum

55
Q

Auricle

A

Flap of elastic cartilage
Rim= helix
The ear you see

56
Q

External auditory canal

A

Curved tube inside temporal bone

Leads to eardrum.

57
Q

Tympanic membrane

A

AKA eardrum

Partition between outer and middle ear

58
Q

Ceruminous glands

A

Secrete earwax

Near external opening of external auditory canal

59
Q

Middle ear

A

Small air filled cavity in temporal bone

Extend from tympanic membrane to oval and round windows.

60
Q

Auditory ossicles

A

Three smallest bones in the body

Middle ear.

Malleus
Incus
Stapes

61
Q

Malleus

A

Auditory ossicle
“Handle”
Attached to internal surface of tympanic membrane; head articulates with body of incus.

62
Q

Incus

A

Middle auditory ossicle.
“The stirrup”

Articulate with malleus and head of stapes.

63
Q

Stapes

A

Third auditory ossicle
“Anvil”

Articulates with incus; base fits into oval window.

64
Q

Round window

A

In middle ear
Directly below oval window of stapes

Enclosed by secondary tympanic membrane.

65
Q

Tensor tympani

A

Muscle in middle ear

Limits movement and increases tension on eardrum to prevent damage to inner ear from loud noise.

Mandible branch of trigeminal nerve (V)

66
Q

Stapedius

A

Smallest skeletal muscle

Middle ear

Dampens large vibrations in stapes; protects oval window but also decreases sensitivity of hearing.

Facial nerve (VII)

67
Q

Hyperacusia

A

Abnormally sensitive hearing

Associated with paralysis of stapedius muscle. (CN V)

68
Q

Auditory tube

A

AKA pharyngotympanic or Eustachian tube.

Connects middle ear with nasopharynx. Normally closed at the medial end.

Opens to equalize pressure between middle ear and atmosphere.

69
Q

What can result from pressure imbalance between middle ear and atmosphere?

A

Pain
Vertigo
Hearing impairment
Ringing in ears.

70
Q

Inner ear

A

AKA the labyrinth

Composed of bony and membranous labyrinth.

71
Q

Bony labyrinth can be divided into what three areas

A

Semicircular canals
Vestibule
Cochlea

72
Q

The bony labyrinth is lined with ___________ and filled with ____________.

A

Periosteum

Perilymph.

73
Q

What sections of the inner ear are involved in equilibrium? With hearing?

A

Equilibrium: semicircular canals and vestibule

Hearing: cochlea

74
Q

Components of the membranous labyrinth

A
Utricle
Saccule 
Ampulla 
Cochlea
Semicircular canals
75
Q

What parts of the inner ear are contained within the vestibule?

A

Utricle

Saccule

76
Q

The membranous canal is lined with _________ and contains ___________?

A

Epithelium

Endolymph

77
Q

Perilymph

A

In bony labyrinth

Similar to CSF. Rich in K+

78
Q

The cochlea makes ______ spiral turns around a centre called the _______

A

Three

Modiolus

79
Q

Orientation of the semicircular canals

A

Anterior and posterior: vertically

Lateral: horizontally

80
Q

Ampulla

A

Large swelling at end of each semicircular canal

81
Q

Semicircular duct

A

Portion of labyrinth that lies within the semicircular canals.

Connect with urtricle of vestibule.

82
Q

Vestibulaocochlear Nerve

A

CN VIII

Vestibular branch: ampullary, utricular, and saccular nerves.

Cochlear branch: spiral ganglion in bones modiolus.

83
Q

Hearing in a nutshell

A
  1. Auricle directs sound waves into external auditory canal
  2. Tympanic membrane vibrates
  3. The malleus in the middle ear vibrate, then the incus, then the stapes
  4. Oval window membrane vibrates and pushes into perilymph.
  5. Pressure waves in perilymph deform walls of scala vestibuli and scala tympani.
  6. Scala V & T push vestibular membrane back and forth, creating pressure waves in endolymph inside cochlear duct.
  7. Basilar membrane vibrates, which moves hair cells of spiral organ, which bends stereocilia.
  8. Nerve impulse generated.
84
Q

Oval window vibration vis á vis the eardrum

A

About 20 X more vigorously.

Ossicles transmit vibrations over a smaller surface area.

85
Q

Three channels of the cochlea

A

Cochlear duct
Scala vestibuli
Scala tympani

86
Q

Scala vestibuli

A

In cochlea. Part of bony labyrinth.
Above cochlear duct
From oval window to helicotrema

87
Q

Scali tympani

A

In cochlea. Part of bony labyrinth.
Below cochlear duct

Helicotrema to round window.

88
Q

Vestibular membrane

A

Separates scala vestibuli from cochlear duct

89
Q

Basilar membrane

A

Separates cochlear duct from scala tympani.

90
Q

Spiral organ

A

AKA organ of Corti
In circular duct, resting on basilar membrane

Coiled sheet of epithelial cells and 16000 hair cells (receptor cells)

Hairs continue stereocilia which project into endolymph.

91
Q

Inner hair cells

A

On spiral organ

Arranged in single row
Synapse with 90-95% first order neurons.

92
Q

Outer hair cells

A

On spiral organ

Rows of three
Outnumber inner hair cells 3:1
Synapse with 90% of motor neurons in cochlear nerve

93
Q

Tectorial membrane

A

Covers hairs of spiral organ

94
Q

Pitch

A

Frequency of sound vibrations

Measured in Hz

95
Q

Volume

A

Amplitude of sound waves.

Measured in dB.
Uncomfortable at 120 dB, pain at 140.

96
Q

Two types of deafness

A

Nerve deafness

Conduction deafness

97
Q

Otosclerosis

A

A form of conduction deafness caused by hardening of the ossicles

98
Q

Pitch and basilar membrane

A

High frequency –> near base of cochlea (stiff and narrow)

Low frequency –> apex of cochlea (flexible and wide)

99
Q

Sound heard best by human ears

A

1000-4000 Hz.

100
Q

Two types of equilibrium

A
  1. Static

2 Dynamic

101
Q

Static Equilibrium

A

Maintenance of body position relative to force if gravity

Tilting head
Linear acceleration/deceleration

Utricle and saccule

102
Q

Dynamic equilibrium

A

Maintenance of body position in response to rotational acceleration or deceleration.

Semicircular canals

103
Q

Vestibular apparatus

A

Receptor organs foe equilibrium

Saccular
Utricle
Semicircular ducts.

104
Q

Utricle and saccula

A

Sacs in the vestibule of the inner ear

Otolithic organs

Receptors for static equilibrium

Contain maccula

105
Q

Macula

A

Thick sensory epithelium within the saccule and utricle

Contains supporting cells, stereocilia and one kinocilium

Overlaid with otolithic membrane, containing otoliths.

106
Q

Positioning of otolithic organs

A

Saccule: vertical (stimulated more by vertical acceleration)

Utricle: horizontal (stimulate more by horizontal acceleration)

107
Q

Hair bends toward kinocilium:

A

Depolarization: receptor potential

108
Q

Hair bends away from kinocilium

A

Hyper polarization

109
Q

Semicircular canals

A

Contain endolymph

Dynamic equilibrium

Lie at right angles to each other

110
Q

Anterior semicircular canal

A

Vertical in the frontal plane

Detects side tilt

111
Q

Posterior semicircular canal

A

Vertical in sagittal plane

Detects yes nod

112
Q

Lateral semicircular canal

A

Horizontal

Detects head shake

113
Q

Ampulla

A

Swollen section of the semicircular canal

Contains cristae

114
Q

Cristae

A

Elevated ridge of the ampulla, which contains hair cells and supporting cells

Covered by cupula

115
Q

Equilibrium receptor potentials are created by:

A

Utrucle and saccule: movement of otoliths on otolithic membrane, causing stereocilia to distort.

Semicircular canals: movement of endolymph again cupula pushing hair in opposite direction as head.

116
Q

Main Equilibrium pathway

A

Stereocilia bend
Receptor potential generated in vestibular axons
Glutamate released

Action potential generated in CN VIII (vestibular branch):FIRST ORDER
[cell bodies in vestibular ganglion]

Synapse in Vestibular Nuclei in pons and medulla
(Some fibres go directly to inferior cerebellar peduncle)

SECOND ORDER NEURON to Ventral Posterior nuclei in thalamus

THIRD ORDER NEURON: to Vestibular Area in parietal lobe

117
Q

The vestibular nuclei also receives input from

A

Eyes

Proprioceptors (especially head and limbs)

118
Q

The vestibular nuclei also sends efferent signals to

A
  1. nuclei for CN III, IV, VI (eye movement)
  2. Nuclei for CN XI (traps and SCM)
  3. Vestibulospinal tract (maintain muscle tone)
119
Q

Age related changes in the eye

A
Presbyopia 
Cataracts
Weakening pupil muscles
Macular disease
Detached retinas
Glaucoma
Decreased tear production
Decreased colour perception nod acuity
120
Q

Presbycusis

A

Age related hearing loss

Damaged/lost hair cells in organ of coti or degeneration of nerve

121
Q

Cataract

A

Loss of transparency of the lens

Most common cause of blindness

122
Q

Glaucoma

A

High interocular pressure which destroys neurons in retina

Second most common cause of blindness

123
Q

Meinere’s syndrome

A

Malfunction of inner ear

Deafness, loss of equilibrium

124
Q

Otitis media

A

Ear infection

Often strep

125
Q

Learning

A

Ability to acquire new memory or skills

126
Q

Memory

A

Process by which knowledge is retained over time

127
Q

Plasticity

A

The capacity of the brain to create persistent functional change

128
Q

Consolidation of memory

A

Conversion of short term into long term memory

129
Q

Anterograde amnesia

A

Can’t create new memories after event

130
Q

Retrograde amnesia

A

Can’t recall memories from before event

131
Q

Receptor potentials generated by stereocilia involve what ions?

A

Ca+

K+

132
Q

Cotton wool spots

A

Sign of diabetes in eye

133
Q

Big tortuous blood vessels in eye

A

Hypertension