Special Senses Flashcards
1
Q
What are the chemical senses?
A
Olfaction
Gustation
2
Q
Olfactory epithelium
A
5 cm squared; 10-100 million receptors
Covers superior nasal cavity and cribiform plate
3
Q
What type of cells are contained within the olfactory epithelium?
A
Olfactory receptor
Support
Basal
Bowman’s (olfactory) glands
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)
5
Q
Olfactory Supporting cells
A
Columnar epithelial cells
Provide physical support, nourishment, insulation to receptor cells
6
Q
Basal olfactory cells
A
Stem cells
Produce new receptors or supporting cells
7
Q
Bowman’s Glands
A
Produce nasal mucous
In the nasal epithelium
8
Q
What cranial nerve innervates nasal glands and epithelium?
A
CN VII Facial
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
10
Q
Olfactory adaptation
A
Initially very fast (50% in first second), then slower
11
Q
Cribiform plate
A
In ethmoid bone
Contains 20 foramina (per nostril) to allow passage of olfactory nerves
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)
13
Q
Location of olfactory bulb
A
Just below frontal lobes
Lateral to crista galli of ethmoid\
Acts as a filter
14
Q
Location of Primary Olfactory area
A
Brodmans 34
Inferior-medial temporal lobe
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
16
Q
Periglomerular cells
A
Interneurons which synapse within and between glomeruli
17
Q
Anosmia
A
Absence of smell
18
Q
Hyposmia
A
Reduced sense of smell
19
Q
Dysosmia
A
Distortion of sense of smell
20
Q
Cacosmia
A
Form of dysosmia, in which things smell baaa-aad
21
Q
Parosmia
A
Sensation of smell in the absence of appropriate stimuli
22
Q
Phantosmia
A
Olfactory hallucination
Uncinate fits
23
Q
Sweet
A
Activated by sugars, alcohol and some amino acids.
Measured by sucrose
Indicates energy rich foods
24
Q
Salty
A
Activated by metal ions (especially Na+)
Measure by Na+
Indicates electrolyte-rich foods
25
Sour
Activated by H+ ions (acids)
Measured by HCl
Aversive
26
Bitter
Lowest threshold receptor
Activated by alkaloids (caffeine, nicotine)
Measured by quinine
Aversive
27
Umami
Activated by glutamate and aspartate
Indicate foods high in amino acids.
28
Where are taste buds found?
Tongue
Soft palate
Epiglottis
Pharynx
29
Papillae
Elevations on tongue.
Circumvallate, fungiform and folate contain taste buds.
Filiform contain tactile receptors.
30
(Circum)vallate papillae
12 found on posterior tongue (inverted V).
Contain 100-300 taste buds each
Innervated by glossopharyngeal nerve (IX)
31
Fungiform papillae
Mushroom shaped
All over tongue
Contain 5 taste buds each.
32
Folate papillae
On lateral tongue. Usually disappear by the end of childhood
33
Filiform papillae
All over tongue.
Contain tactile receptors (texture) but no taste buds.
Help move food
Trigeminal nerve (V).
34
5 basic taste receptors
1. sweet
2. salty
3. sour
4. bitter
5. umami
35
How many taste buds?
Around 10000
36
Three type of cells in a taste bud
Gustatory receptor
Supporting cells
Basal cells
37
How frequently are new gustatory cells produced?
10 days (olfaction about 30 days)
38
What nerve is responsible for taste in the anterior 2/3 of the tongue?
Facial nerve (VII)
39
What nerve is responsible for taste in the posterior 1/3 of the tongue, including vallate papillae?
Glossopharyngeal (IX)
40
What nerve is responsible for taste in the palate and epiglottis?
Vagus (X)
41
What nerve is responsible for the sensation of texture when chewing?
Trigeminal (V)
42
How many gustatory receptors per taste bud?
About 50
43
How do the various tastands generate receptor potentials?
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.
44
What NT is released by the gustatory receptor cells?
ATP
45
Gustatory pathway
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)
46
Gustatory adaptation
Quick (1-2 min)
Involves gustatory receptors, olfactory receptors, CNS pathways
47
How many sensory receptors are in the eye?
More than half
48
How much of the eyeball is in the orbit?
7/8
49
Palpabrae
Eyelids
Protect and lubricate, provide shade
```
Epidermis
Dermis
Tarsal plate
Tarsal glands
Conjunctiva
```
50
Conjunctiva
Mucous membrane that lines inner eyelid and covers sclera
Stops at edge of cornea
Bulbar and palpabrael
51
Tarsal plate
Part of Palpabrae
Provides structural support
52
Tarsal glands
In tarsal plate of Palpabrae
Secrete meibom (prevents eyelids from sticking together)
53
Three regions of the ear
Outer ear
Middle eat
Inner ear
54
Outer ear consists of
Auricle
External auditory canal
Eardrum
55
Auricle
Flap of elastic cartilage
Rim= helix
The ear you see
56
External auditory canal
Curved tube inside temporal bone
| Leads to eardrum.
57
Tympanic membrane
AKA eardrum
Partition between outer and middle ear
58
Ceruminous glands
Secrete earwax
Near external opening of external auditory canal
59
Middle ear
Small air filled cavity in temporal bone
Extend from tympanic membrane to oval and round windows.
60
Auditory ossicles
Three smallest bones in the body
Middle ear.
Malleus
Incus
Stapes
61
Malleus
Auditory ossicle
"Handle"
Attached to internal surface of tympanic membrane; head articulates with body of incus.
62
Incus
Middle auditory ossicle.
"The stirrup"
Articulate with malleus and head of stapes.
63
Stapes
Third auditory ossicle
"Anvil"
Articulates with incus; base fits into oval window.
64
Round window
In middle ear
Directly below oval window of stapes
Enclosed by secondary tympanic membrane.
65
Tensor tympani
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
Stapedius
Smallest skeletal muscle
Middle ear
Dampens large vibrations in stapes; protects oval window but also decreases sensitivity of hearing.
Facial nerve (VII)
67
Hyperacusia
Abnormally sensitive hearing
Associated with paralysis of stapedius muscle. (CN V)
68
Auditory tube
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
What can result from pressure imbalance between middle ear and atmosphere?
Pain
Vertigo
Hearing impairment
Ringing in ears.
70
Inner ear
AKA the labyrinth
Composed of bony and membranous labyrinth.
71
Bony labyrinth can be divided into what three areas
Semicircular canals
Vestibule
Cochlea
72
The bony labyrinth is lined with ___________ and filled with ____________.
Periosteum
| Perilymph.
73
What sections of the inner ear are involved in equilibrium? With hearing?
Equilibrium: semicircular canals and vestibule
Hearing: cochlea
74
Components of the membranous labyrinth
```
Utricle
Saccule
Ampulla
Cochlea
Semicircular canals
```
75
What parts of the inner ear are contained within the vestibule?
Utricle
| Saccule
76
The membranous canal is lined with _________ and contains ___________?
Epithelium
| Endolymph
77
Perilymph
In bony labyrinth
Similar to CSF. Rich in K+
78
The cochlea makes ______ spiral turns around a centre called the _______
Three
Modiolus
79
Orientation of the semicircular canals
Anterior and posterior: vertically
Lateral: horizontally
80
Ampulla
Large swelling at end of each semicircular canal
81
Semicircular duct
Portion of labyrinth that lies within the semicircular canals.
Connect with urtricle of vestibule.
82
Vestibulaocochlear Nerve
CN VIII
Vestibular branch: ampullary, utricular, and saccular nerves.
Cochlear branch: spiral ganglion in bones modiolus.
83
Hearing in a nutshell
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
Oval window vibration vis á vis the eardrum
About 20 X more vigorously.
Ossicles transmit vibrations over a smaller surface area.
85
Three channels of the cochlea
Cochlear duct
Scala vestibuli
Scala tympani
86
Scala vestibuli
In cochlea. Part of bony labyrinth.
Above cochlear duct
From oval window to helicotrema
87
Scali tympani
In cochlea. Part of bony labyrinth.
Below cochlear duct
Helicotrema to round window.
88
Vestibular membrane
Separates scala vestibuli from cochlear duct
89
Basilar membrane
Separates cochlear duct from scala tympani.
90
Spiral organ
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
Inner hair cells
On spiral organ
Arranged in single row
Synapse with 90-95% first order neurons.
92
Outer hair cells
On spiral organ
Rows of three
Outnumber inner hair cells 3:1
Synapse with 90% of motor neurons in cochlear nerve
93
Tectorial membrane
Covers hairs of spiral organ
94
Pitch
Frequency of sound vibrations
Measured in Hz
95
Volume
Amplitude of sound waves.
Measured in dB.
Uncomfortable at 120 dB, pain at 140.
96
Two types of deafness
Nerve deafness
| Conduction deafness
97
Otosclerosis
A form of conduction deafness caused by hardening of the ossicles
98
Pitch and basilar membrane
High frequency --> near base of cochlea (stiff and narrow)
Low frequency --> apex of cochlea (flexible and wide)
99
Sound heard best by human ears
1000-4000 Hz.
100
Two types of equilibrium
1. Static
| 2 Dynamic
101
Static Equilibrium
Maintenance of body position relative to force if gravity
Tilting head
Linear acceleration/deceleration
Utricle and saccule
102
Dynamic equilibrium
Maintenance of body position in response to rotational acceleration or deceleration.
Semicircular canals
103
Vestibular apparatus
Receptor organs foe equilibrium
Saccular
Utricle
Semicircular ducts.
104
Utricle and saccula
Sacs in the vestibule of the inner ear
Otolithic organs
Receptors for static equilibrium
Contain maccula
105
Macula
Thick sensory epithelium within the saccule and utricle
Contains supporting cells, stereocilia and one kinocilium
Overlaid with otolithic membrane, containing otoliths.
106
Positioning of otolithic organs
Saccule: vertical (stimulated more by vertical acceleration)
Utricle: horizontal (stimulate more by horizontal acceleration)
107
Hair bends toward kinocilium:
Depolarization: receptor potential
108
Hair bends away from kinocilium
Hyper polarization
109
Semicircular canals
Contain endolymph
Dynamic equilibrium
Lie at right angles to each other
110
Anterior semicircular canal
Vertical in the frontal plane
| Detects side tilt
111
Posterior semicircular canal
Vertical in sagittal plane
Detects yes nod
112
Lateral semicircular canal
Horizontal
Detects head shake
113
Ampulla
Swollen section of the semicircular canal
Contains cristae
114
Cristae
Elevated ridge of the ampulla, which contains hair cells and supporting cells
Covered by cupula
115
Equilibrium receptor potentials are created by:
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
Main Equilibrium pathway
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
The vestibular nuclei also receives input from
Eyes
Proprioceptors (especially head and limbs)
118
The vestibular nuclei also sends efferent signals to
1. nuclei for CN III, IV, VI (eye movement)
2. Nuclei for CN XI (traps and SCM)
3. Vestibulospinal tract (maintain muscle tone)
119
Age related changes in the eye
```
Presbyopia
Cataracts
Weakening pupil muscles
Macular disease
Detached retinas
Glaucoma
Decreased tear production
Decreased colour perception nod acuity
```
120
Presbycusis
Age related hearing loss
Damaged/lost hair cells in organ of coti or degeneration of nerve
121
Cataract
Loss of transparency of the lens
Most common cause of blindness
122
Glaucoma
High interocular pressure which destroys neurons in retina
Second most common cause of blindness
123
Meinere's syndrome
Malfunction of inner ear
Deafness, loss of equilibrium
124
Otitis media
Ear infection
Often strep
125
Learning
Ability to acquire new memory or skills
126
Memory
Process by which knowledge is retained over time
127
Plasticity
The capacity of the brain to create persistent functional change
128
Consolidation of memory
Conversion of short term into long term memory
129
Anterograde amnesia
Can't create new memories after event
130
Retrograde amnesia
Can't recall memories from before event
131
Receptor potentials generated by stereocilia involve what ions?
Ca+
| K+
132
Cotton wool spots
Sign of diabetes in eye
133
Big tortuous blood vessels in eye
Hypertension
