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Brain and Behaviour > Audition and chemical senses > Flashcards

Audition and chemical senses Flashcards

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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
Q

How does hearing loss occur?

A

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
Q

What happens in age-related hearing loss?

A

↑ = in men

Freq. sensitive depends on age

33,011,778 ears

27
Q

How do cochlea implants work to bypass degenerated inner hair cells?

A

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
Q

How are odours important?

A

Key in detecting potential dangers + opportunities for food/ social interactions
- short + long-range signalling

29
Q

Why are flavours important?

A

Help identify spec. food + food qual. + support learning assoc. between tastes + emotional events (i.e malaise)
- short-range signalling

30
Q

What are chemical senses?

A

Smell and taste

Important bc motivated + emotional bhvrl response = ↑ influenced by presence of chemical signals

31
Q

How is olfaction linked to bhvr?

A

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
Q

How relevant is smell to humans?

A

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
Q

Describe scent tracking in animals.

A

Bloodhound tracking a pheasant scent

34
Q

Describe scent tracking in people.

A

People tracked chocolate scent (Porter et al. 2007)

35
Q

How does the human nose work?

A

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
Q

What cells types are in the olfactory epithelium?

A

Supporting cells = metabolic + physical support

Basal cues = olfactory cell progenitors

Olfactory sensory neurons (OSN) = detect doors + produce mucus. Replaced constantly by basal cell.

37
Q

How do olfactory receptors work in the nose?

A

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
Q

Why are olfactory receptors important?

A

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
Q

Describe the olfactory pathways.

A

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
Q

How can olfaction change?

A

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
Q

What is olfactory fatigue?

A

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
Q

How is taste and bhvr linked?

A

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
Q

How is taste, odors and flavour occur whilst eating?

A

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
Q

What is the structure of taste sensors?

A

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
Q

How are taste buds and taste receptors linked?

A

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
Q

What are the 3 types of receptor types?

A

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
Q

What are the different types of taste receptors

A

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
Q

What the taste neural pathways?

A

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
Q

What is salty like as a class?

A

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
Q

What is sour like as a class?

A

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
Q

What is sour like as a class?

A

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
Q

What is bitter like as a class?

A

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
Q

What are taste mediated bhvrs?

A

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

Brain and Behaviour (9 decks)

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