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BIOL373 > Unit 3b - Special Senses > Flashcards

Unit 3b - Special Senses Flashcards

1
Q

What is special about olfaction?

A

the only sensory modality that does not go first to thalamus; does not cross the midline
- the only special sense for which the sensory cell itself is the neuron that carries the info to the CNS

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2
Q

What is olfactory epithelium?

A

lines the nasal cavity, with embedded primary sensory neurons called olfactory sensory neurons

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3
Q

What is olfactory receptor neurons (ORNs)?

A

bipolar neurons (neurons that have 2 extensions, 1 axon and 1 dendrite) which are replaced ~60 days
- dendrites end in non-motile cilia which express odorant receptor proteins
- axons end go through gaps in cribiform plate; synapse on 2nd order neurons

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4
Q

What are odorant receptor proteins?

A

are GPCRs, which form one of the largest gene families in vertebrates (3-5% of the genome) and there are 1000s of different types of receptors

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5
Q

How do you code for olfactory?

A

each olfactory receptor neuron expresses only one type of odorant receptor protein, but each receptor can recognize more than one odorant, and each odorant can stimulate more than one receptor

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6
Q

What is gustation?

A

combination of five basic tastes: sweet, sour, salty, bitter, and umami

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7
Q

What is sweet taste triggered by?

A

carbohydrates, which convert to energy

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8
Q

What is sour taste triggered by?

A

presence of H+

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9
Q

What is salty taste triggered by?

A

presence of Na+

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10
Q

What is bitter taste triggered by?

A

many compounds, warns of possible toxicity

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11
Q

What is umami taste triggered by?

A

glutamate, some nucleotides (protein)

its a basic taste that enhances the flavour of foods eg. MSG

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12
Q

What type of cells are taste receptor cells?

A

non-neural epithelial cells which frequently come into contact with harmful/poisonous chemicals so it is replaced every 10 days

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13
Q

How many taste receptor cells are on each taste bud?

A

about 50-150

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14
Q

What is the taste transduction process?

A
  1. ligands activate GPCR on taste receptor cell
  2. various intracellular pathways activated
  3. Ca2+ signal triggers exocytosis or ATP formation
  4. neurotransmitter or ATP released
  5. primary sensory neuron fires; APs sent to brain
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15
Q

What are the structures part of the external ear?

A
  1. pinna
  2. ear canal
  3. tympanic membrane
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16
Q

What is pinna?

A

important accessory structure that directs sound waves into the ear, varies in shape and location from species and depends on animals’ survival needs

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17
Q

What is ear canal?

A

sealed at its internal end by the tympanic membrane

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18
Q

What is tympanic membrane?

A

a thin membranous sheet of tissue that separates external ear from the middle ear

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19
Q

What are the structures part of the middle ear?

A
  1. malleus, incus, stapes
  2. eustachian tube
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20
Q

What is malleus, incus, and stapes?

A

three small bones that conduct sound from the external environment to the inner ear
- they’re connected together with hinges
- one end of malleus connected to tympanic membrane, and one end of stapes attached to a thin membrane separating the middle and inner ear

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21
Q

What is eustachian tube?

A

connects the middle ear with the pharynx; it is normally collapsed, sealing off the middle ear, but it opens shortly to allow middle ear pressure to equilibrate with atmospheric pressure during chewing, swallowing, and yawning

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22
Q

What are the structures part of the inner ear?

A

vestibular apparatus and semicircular canals, cochlea, oval window and round window, vestibbulocochlear nerve

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23
Q

What is vestibular apparatus and semicircular canals?

A

the sensory transducer for our sense of equilibrium

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24
Q

What is cochlea?

A

contains sensory receptors for hearing (snail shell shape)

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25
Q

What is oval window (attached to stapes) and round window?

A

separates the lliquid-filled cochlia with air-filled middle ear

26
Q

What is vestibulocochlear nerve?

A

leads from inner ear to the brain

27
Q

How does sound transmit through the ear?

A
  1. sound waves strike the tympanic membrane and become vibrations
  2. the sound wave energy is transferred to the three bones of the middle ear, which vibrate
  3. the stapes is attached to the membrane of the oval window. vibrations of the oval window create fluid waves within the cochlea
  4. the fluid waves push on the flexible membranes of the cochlea duct. hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter release
  5. neurotransmitter release onto sensory neurons creates action potentials that travel through the cochlear nerve to the brain
  6. energy from the waves transfer across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window
28
Q

What are the 3 fluid filled channels in the cochlea?

A
  1. vestibular duct
  2. cochlear duct
  3. tympanic duct
29
Q

What is vestibular duct?

A

continuous with tympanic dust and connects at tip of the cochlea
- fluid is similar to plasma called perilymph (low K+, high Na+)

30
Q

What is cochlear duct?

A

a dead end tube filled with endolymph secreted by epithelial cells in the duct
- endolymph Is similar to intracellular fluid (high K+, low Na+)
- contains the organ of Corti which are sensory hair cells that support cells, and creates oscillations when waves travel through the cochlea

31
Q

What is tympanic duct?

A

continuous with vestibular duct and has fluid similar to plasma called perilymph (low K+, high Na+)

32
Q

What are hair cells?

A

nonneural receptor cells
- the surface of each hair cell has 50-100 stiffened cilia called stereocilia arranged in ascending height

33
Q

What is the Place Code Hypothesis for coding for pitch?

A

sound waves trigger activity at different places along the cochlea’s basilar membrane and are perceived as different pitches eg. piano
- wave travels along cochlea, hair cells in areas that bend the most at a given frequency encode that pitch

34
Q

What is the Temporal Code Hypothesis for coding for pitch?

A

frequency of sound waves determine frequency of action potentials travelling along auditory nerve, perceived as pitch
eg. low frequency sound is slow waves along basilar membrane which means low firing rate of primary afferent neurons and is then perceived as low pitch sound

problem: we can hear up to 20,000 Hz but no neuron can transmit at this rate

35
Q

What is the current hypothesis for coding for pitch?

A

multiple neurons with staggered firing rates carry the temporal code
- place coding (which region / hair cells along basilar membrane are stimulated) also plays a role
- relative important of place and temporal coding depends on pitch (low pitch is temporal coding, and high pitches is place coding)

36
Q

What happens during hearing loss?

A
  1. conductive - no transmission through either external or middle ear eg. issues with earwax or fluid in middle ear (can usually be repaired)
  2. central - damage to neural pathway between ear and cerebral cortex or damage to cortex itself eg. stroke (uncommon)
  3. sensorineural - damage to structures of inner ear eg. death of hair cells due to loud noises (common in young and elderly, but hair cells cannot be replaced)
37
Q

What are the 2 components of the special sense of equilibrium?

A
  1. dynamic component - movement of body through space
  2. static component - position of head (if its in a normal upright position)
38
Q

What is vestibular apparatus?

A

an intricate series of interconnected fluid-filled chambers that consists of octolith organs and semicircular canals; like the cochlear duct, is filled with high K+ and low Na+

39
Q

What is octolith organs?

A

saccule and utricle, tells us about linear acceleration and head position

40
Q

What is semicircular canals?

A

superior, horizontal, and posterior; they sense rotational acceleration in various directions, and are oriented at right angles to one another

41
Q

What are hair cells grouped in that detect spin (rotational acceleration)?

A

hair cells are grouped in cristae, within ampulla of canals

42
Q

What are hair cells grouped in that detect forward/backward acceleration and vertical acceleration?

A

hair cells grouped in maculae, within utricles/saccules
utricle - forward/backward acceleration, head tilt
saccule - vertical acceleration

43
Q

What is the pupil?

A

an opening through which light can pass into the interior of the eye
- pupil sizes varie with contraction and relaxation
- appears as the black spot inside the coloured ring of pigment known as the iris (pigments and other components of the iris determine eye colour)

44
Q

What is the lens?

A

a transparent disk that focuses light and separates the 2 compartments of the eye

45
Q

What is the aqueous humor?

A

a low protein plasma-like fluid secreted by the ciliary epithelium supporting the lens

46
Q

What is the cornea?

A

a transparent disk of tissue that is a continuation of the sclera
- light from environment enters the anterior surface of the eye through the cornea

47
Q

How is light modified?

A
  1. the amount of light that reaches photoreceptors is modulated by changes in size of pupil
  2. the light is focused by changes in shape of lens
48
Q

What is the retina?

A

light-sensitive lining of the eye that contains the photoreceptors

49
Q

What is optic disk (blind spot)?

A

region where optic nerve and blood vessels leave the eye
crisscrossed small arteries and veins that radiate out from one spot in the retina
- where neurons of the visual pathway form the optic nerve and exit the eye
- lateral to the optic disk is a small dark spot, the fovea

50
Q

What is the pupillary light reflex?

A

control of pupil diameter according to intensity of light

autonomic reflex:
detector: photoreceptors in retina
afferent: afferent neurons travelling in optic nerve
integrating centre: thalamus/brainstem (midbrain)
efferent: motor neurons travelling in oculomotor nerve
effectors: smooth muscles regulating pupil diameter (circular is constriction- parasympathetic; radial is dilation- sympathetic)

51
Q

What is phototransdunction?

A

converting light into changes in membrane potential by photoreceptor cells inretina

52
Q

What are the photoreceptors?

A

neurons that convert light energy to electrical energy
rods and cones

53
Q

What are rod?

A

photoreceptors that function well in low light. andare used in night vision, when objects are seen in black and white
- they outnumber cones by 21:1 ratio, except in the fovea, which only contains cones

54
Q

What is cones?

A

photoreceptors that are responsible for high-acuity vision and colour vision during the daytime
- fovea, the region of sharpest vision, has a high density of cones and is also free of neurons and blood vessels that would block light reception

55
Q

What is pigment epithelium?

A

absorbs any light rays that escape the photoreceptors, preventing distracting light from reflecting inside eye and distorting images

55
Q

What is pigment epithelium?

A

absorbs any light rays that escape the photoreceptors, preventing distracting light from reflecting inside eye and distorting images

56
Q

Where are photoreceptors located?

A

photoreceptors (rods and cones) are located at the bottom layer, with their photosensitive tips against the pigment epithelium

57
Q

What are ganglion and bipolar cells?

A

neurons where signals from rods and cones are integrated
- sensory information about light passes from the photoreceptors to bipolar neurons, then to a layer of ganglion cells

58
Q

What is fovea?

A

free of neurons and blood vessels that would block light reception, so photoreceptors receive light directly

59
Q

What is the basic structure of the 2 photoreceptors?

A
  1. an outer segment whose tip touches the pigment epithelium of the retina
  2. an inner segment that contains the cell nucleus and organelles for ATP and protein synthesis
  3. basal segment with a synaptic terminal that releases glutamate onto bipolar cells
60
Q

What takes place in the outer segment?

A

light transduction takes place in the outer segment of the photoreceptor using visual pigments (transducers that convert light energy into a change in membrane potential eg. rhodopsin) in membrane disks

BIOL373 (3 decks)

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