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Audition and chemical senses Flashcards

1
Q

What do sensory systems do?

A

Each sense captures stimuli (info) from the environment/ other indvdls.

Touch = mechanical stimulation + temperature
Sight = light
Hearing = sound
Smell = volatile chemicals
Taste = soluble chemicals

Stimulus -> sensory organ -> brain activity

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2
Q

What are the functions of hearing?

A

Sounds = carry important info abt others + surroundings .

We can detect diff. sound attributes through complexity, intensity + frequency

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3
Q

What is sounds?

A

Produced by vibrating objects = vibrations displace the surrounding medium (liquid, air), creating pressure changes.

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4
Q

Describe frequency as a psychosocial property of sound.

A

Frequency = cycles per time unit.

Measured in Hertz = 1 cycle per second

Perceived as pitch = diff. animals are sensitive. to/ can detect sounds in diff. freq. range

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5
Q

Describe amplitude as a psychosocial property of sound.

A

Changes in magnitude of sound, but same frequency.

Measured in decibels (dB)

Perceived as loudness = diff. every-day sounds have diff. intensities

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6
Q

Describe complexity as a psychosocial property of sound.

A

Frequency composition.

Varies from a pure tone (single frequency) to a mix. of frequencies

Perceived as sound quality = complex sounds are the most common. Pure tones (single freq.) is rare in the environment

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7
Q

Describe complexity as a psychosocial property of sound.

A

Frequency composition.

Varies from a pure tone (single frequency) to a mix. of frequencies

Perceived as sound quality.

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8
Q

What is sound detection?

A

Auditory system = can identify change in air pressure across time in a freq. spec. manner

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9
Q

What is sound perception?

A

Human ears = perceive each
indvdl frequency + its amplitude, variation, independently.

Sound perception = only the beginning of auditory experience.

Brain receives the info of sound detection + assigns meaning to it.

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10
Q

How is the human ear structured?

A

Ear = outer, middle + inner ear

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11
Q

What is the function of the outer ear?

A

Captures + amplifies sound waves:
Made up of the Pinnae -> Ear canal -> Tympanic membrane (vibrates bc of vibration in air)

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12
Q

What is the function of the middle ear?

A

Amplifies + transmit vibrations:

Air filled cavity occupied by ossicles = 3 smallest bones in the human body: Malleus, Incus + Stapes

Ossicles vibrate bc of tympanic vibration in membrane. Amplify + transmit sounds to inner ear (oval window)

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13
Q

What is the function of the inner ear?

A

Translates vibrations into neural activity:
- Vestibular organ = balance (no function w/ hearing)
- Cochlear = 2 windows (oval = pressure comes from the middle ear, round = dissipate the pressure of the vibration after the inner ear has detected sound.

Auditory nerve = collect al the info + send to the Brian

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14
Q

What is inside the cochlea?

A

Extension of cochlea = organ of Corti + basilar membrane inside corti.

Basilar membrane = will activate depending on the freq. of the sound.

The tip of the membrane = 5x wider + 100x less stiffer than the base - difference makes it sens. to different frequencies of sound e.g 400 Hz will activate the apex (tip)

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15
Q

What is basilar membrane tonotopy?

A

Tonotopy = tones spatial agreement.

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16
Q

How does the pressure transmit along the canals?

A

Vibration of the stapes, push + pull the flexible oval window in + out of the vestibular canal at the base of cochlea

Pressure waves deflect the basilar membrane in a frequency spec. manner.

All pressure ends up moving the round window + dissipates

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17
Q

What are the three canals in the cochlea?

A

Vestibular canal
Middle canal
Tympanic canal

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18
Q

What are the importance of hair cells?

A

Outer hair cells = not involved in the perception of sound

Inner hair cells = in charge of detecting the movement of the vascular membrane + transferring the info.

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19
Q

What is the importance of the tectorial membrane to hair cells?

A

Tectorial membrane moves when the basilar membrane moves
- HE, BM is attached on both sides vs TM is attached on 1end (floats above inner hair cells) touching outer hair cells
- projects into the middle canal

The difference in movement between TM + BM = is what the inner hair cells can detect as stimulation
- vibrations = makes stereo cilia bend

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20
Q

What is stereocilia?

A

Hair-like extensions on tips of hair cells. Molecular filaments (tip link) connect the tip of each cilia to neighbouring potassium channels

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21
Q

How does stereocilia work to translate vibration into neural activity?

A

Restaing state (no sound) = basal K+ influx + neurotransmitter release

Basilar membrane vibration induce stereocilia bending = ↑ K+ influx + neurotransmitter release @ cell base.

Tip link = mechanically gated channel

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22
Q

How is the frequency coded in the cochlea?

A

Place code = freq. info. coded by the place along the cochlea (in inner hair cells) w/ greatest mechanical displacement (movement of that spec. of the membrane)

23
Q

How is amplitude coded in the cochlea?

A

Amplitude code = louder sounds produce larger vibration of the basilar membrane = inner hair cells release ↑ neurotransmitter

24
Q

What is auditory pathways?

A

Hair cell neurotransmitter release active
bipolar cells = form the auditory nerve (cranial nerve VIII).

Auditory nerve enters the medulla = synapsis in a tonotopic manner (the frequency spatial repre. of the basilar membrane - maintained).

Axons from the cochlear nuclei ascend to the
superior olivary complex in the pons. Inputs
from each ear are processed by both olivary
nuclei (sound source spatial location).

A series of ascending projection along the
midbrain ends up in the primary auditory
cortex (A1). The tonotopic representa.on is
preserved up to A1.

25
How does hearing loss occur?
Declines w/ age/ damage (permanent or temp.) to any component of the auditory pathway Temporary: - Obstruction of the ear canal = damage to the tympanic membrane - conductive hearing loss = probs. in the ossicles (i.e otitis media during ear infections) Permanent: - Otosclerosis = excessive growth of ossicles + requires surgery. - Sensorineural hearing loss (most common defect) bc defects in cochlea/ auditory nerve. Damage to hair cells = toxicity/ excessive exposure to noise
26
What happens in age-related hearing loss?
↑ = in men Freq. sensitive depends on age 33,011,778 ears
27
How do cochlea implants work to bypass degenerated inner hair cells?
Miniature flexible electrode array surgically implanted in the cochlea through oval window Receiver/ stimulator detects + process sound into radio signals = sent to stimulator (implanted inside skull during surgery) Miniature electrodes positioned in freq. spec. regions of the cochlea emit electrical signals + activate neighbouring bipolar cells + auditory nerve
28
How are odours important?
Key in detecting potential dangers + opportunities for food/ social interactions - short + long-range signalling
29
Why are flavours important?
Help identify spec. food + food qual. + support learning assoc. between tastes + emotional events (i.e malaise) - short-range signalling
30
What are chemical senses?
Smell and taste Important bc motivated + emotional bhvrl response = ↑ influenced by presence of chemical signals
31
How is olfaction linked to bhvr?
Humans have food door discrimination, but have diff. describing what they smell Olfactory cues = support diverse bhvrs: - Food/ mate seeking - Feeding - Co-spec. identification (group/ non-member) - Marking territories - Reproduction - Agression + early warning
32
How relevant is smell to humans?
generally accepted = animals rely on olfaction > humans Dogs = detect odors 100x less concentrated than humans. Dogs have 100x more receptors. But human + dog olfactory is equally sensitive = respond to 1 single odor molecule
33
Describe scent tracking in animals.
Bloodhound tracking a pheasant scent
34
Describe scent tracking in people.
People tracked chocolate scent (Porter et al. 2007)
35
How does the human nose work?
Primary function = humidify + warm air going to lungs Secondary = olfaction - Air flows onto nose cavity - Odorants interact w/ olfactory epithelium - Mucus in the epithelium captures odorants
36
What cells types are in the olfactory epithelium?
Supporting cells = metabolic + physical support Basal cues = olfactory cell progenitors Olfactory sensory neurons (OSN) = detect doors + produce mucus. Replaced constantly by basal cell.
37
How do olfactory receptors work in the nose?
Odorants = recognised by spec. receptors in the cilia of OSNS (olfactory sensory neuron) Olfactory receptors = G-coupled proteins whose activation opens Na+ /Ca2+ channels. OSN = depolarised by Na+ /Ca2+ influx, firing action potentials.
38
Why are olfactory receptors important?
Humans = around 1000 diff. odor receptors = can perceive > a trillion odorants. Shape-pattern theory = each scent — as a function of odorant-shape to OR-shape fit — activate unique arrays of olfactory receptors in the olfactory epithelium. Various arrays = spec firing patterns of neurons in the olfactory bulb - determines the scent we perceive
39
Describe the olfactory pathways.
Axons from OSNs pass through tiny holes in the cribriform plate (bone) to enter the brain. Each type of OSN projects its axon to a single glomerulus within the olfactory bulb. OSN axons make synapsis w/ mitral + tufted cells = project to the primary olfactory cortex + other brain regions
40
How can olfaction change?
Olfaction = subjective experience Detection threshold can be affected by: - Gender = women gen. ↓ thresholds vs men esp. during ovulatory period, sensitivity not heightened during pregnancy - Training = proff. perfumers + wine tasters can distinguish 100,000 odorants - Age = by 85, 50% of population is effectively anosmic (lost smell)
41
What is olfactory fatigue?
Smell detection stops = continuous exposure to odorant. Smell = detector of changes. e.g walking into a coffee shop + can only smell recently- grinded coffee for a few minutes; BC receptor adaptation = continuous exposure to an odorant, makes the receptor stop responding + detection stops. Mechanism = receptor internalisation or Na+ /Ca2+ channel inactivation in the olfactory sensory neuron
42
How is taste and bhvr linked?
Short range info (inside the mouth). Taste recognition = guide appetite + trigger physiological processes 4 absorbing nutrients + adjusting metabolism. Important for identifying nutrients + avoiding chemical threats Culture greatly influences what is good or bad. Liking/ disliking is present in newborns (innate)
43
How is taste, odors and flavour occur whilst eating?
Taste = detection of chemical compounds in the moth by direct contact w/ chemoreceptors on the tongue + roof mouth Retronasal olfactory sensation = perception of odorants while chewing + swallowing food Brain processes odors diff. = depends on if they came from nose/ mouth Flavour = taste (sweet, salty, sour, bitter, umami + fact) + olfaction (retronasal) combination
44
What is the structure of taste sensors?
Arranged in tastebuds = distributed along the tongue, palate, pharynx, epiglottis + upper third of the oesophagus Taste buds arranged in 3 kinds of papillae, distributed in spec. regions of the tongue - Circumvalate papillae - Foliate papillae - Fungiform papillae Receptors for diff. tastes group together in the same bud Receptor activation sends neural signal through taste nerves
45
How are taste buds and taste receptors linked?
Each testbed = several types of taste receptor cells Receptor cells = specialised cells containing microvilli (extensions of cellular membrane) containing receptor proteins There are 3 types of receptor types
46
What are the 3 types of receptor types?
Type 1 = support function Type 2 = detect bitter, sweet + umami. Chemical signal to neighbouring cells (including Type 3) Type 3 = detect sour. Synaptic communication w/ afferent fibers
47
What are the different types of taste receptors
G-coupled protein receptors (like in olfactory neurons) T1R and T2R. T1R detects sweet and umami taste. T2R detects bitter taste. Ion (Na+) channel ENaC detects salty taste.
48
What the taste neural pathways?
3 cranial nerves = collect taste info - Chorda tympani - Glosso-pharyngeal - Vagus Synapse at nucleus of the solitary tract (medulla) = hypothalamus -> insula -> gustatory primary cortex -> orbitofronal cortex (put together w/ other info e.g sensory, memories)
49
What is salty like as a class?
Animals = appetite 4 salt. In low salt environment animals = looking and consuming it. High concentration of salt = aversive, perhaps prevents hypernatremia (high blood Na+ concentration) + dehydration ENaC deletion (receptor for salt) in rodents removes NaCl behavioural taste response in Na+ deprived mice. Bhvr doesn't change. Mice like salt.
50
What is sour like as a class?
From acidic substances High concentrations = acids will damage both external + internal body issues. Acids assoc. w/ increased proton (H+ ) concentration Receptor cells permeate H + = contribute to cell depolarisation+ action potential initiation.
51
What is sour like as a class?
Typically evoked by sugars. T1R receptors responsible for all sweet perception = . G-coupled protein. Induce cell depolarisation + action potentials Many different sugars + artificial sweeteners activate T1R. Mice lacking T1R receptors (T1R2 or T1R3) loose preference for natural and artificial sweeteners.
52
What is bitter like as a class?
Large quant. + qual. of compounds = bitter taste. Bitter substances = poisonous. Quinine = Prototypically bitter-tasting substance. T2R bitter receptors = G-coupled protein. Induce cell depolarisation + action potentials 30 diff. T2R genes suggest certain specificity in bitter sensing.
53
What are taste mediated bhvrs?
Odour detection = helps find food, but taste determines if the food = nutritious/ potential chemical threat. Bitter taste = signal poisonousfood. Intense sour = related to acidic substances, that might cause damage. Sweet + salty tastes = normally induce seeking behaviour since substances increase survival. Infants’ behaviour + facial expressions reveal innate taste preferences

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