Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

4. BIOL257 > Special senses I: olfaction and gustation > Flashcards

Special senses I: olfaction and gustation Flashcards

1
Q

olfaction and gustation: general features

A
  • chemoreceptors
  • continuously renewed
  • chemicals in air/ food dissolved into saliva/ watery nasal mucus
  • bind/ interact w receptors on cell membrane
  • binding causes receptor/ generator (graded) potentials -> AP
  • both pathways incl:
  • via cortex (conscious perception)
  • limbic system (emotional/ behavioural processing)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

olfaction:

A
  • dissolved substances bind to chemoreceptors on sensory neurons in olfactory epithelium at roof of nasal cavity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

olfactory epithelium: layers

A
  • olfactory mucosa (epithelium)

- lamina propria (ct)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

olfactory epithelium mucosa:

A
  • olfactory receptor cells (primary sensory neurons)
  • basal cells (precursors of new olfactory cells)
  • sustentacular cells (structural support)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

olfactory epithelium lamina propria:

A
  • bowman’s glands (secrete mucus) in nasal cavity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

olfactory sensory neurons:

A
  • spiking (AP producing) bipolar neurons w dendrites exposed at lumenal surface of olfactory mucosa
  • dendrites terminate at bulbous olfactory knobs covered in cilia - increase SA
  • ciliary membranes have odourant receptors (G protein coupled receptors) detect odourant at conc. 1 in 10 mil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

olfactory transduction: start

A
  • odorant molecule binds to GPCR on ciliary membrane
  • receptor-odorant complex activates G protein (Golf)
  • G olf activates adenyl cyclase - converts ATP to cAMP
  • [cAMP] in causes cAMP gated Na and Ca cation channels in membrane to open
  • influx of + ions depolarises cell
  • elevated [Ca] opens Ca gated Cl ion channels
  • flow out of -ve ions further depolarises cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

olfactory transduction: from sufficient depolarisation

A
  • generation of AP at axon hillock
  • AP to synaptic terminal
  • release NT glutamate onto dendrites of 2ndary neurons in olfactory bulb
  • rapid adaptation to persistent stimuli
  • Ca depolarising cell may also inhibit cAMP gated ion channels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

olfactory bulb: features

A
  • axons are thin/ unmyelinated
  • small bundles in holes of cribiform plate (CN I: olfactory)
  • axons project into olfactory bulb
  • synapses onto dendrites of mitral cells (M) and tufted cells (T) -> 2ndary neurons and output cells of olfactory bulb
  • synapes located in clusters (neuropils) called glomeruli
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

olfactory bulb: glomeruli contd.

A
  • segregate inputs from specific receptor types before relaying signals to higher brain levels for processing
  • GABAergic periglomerular cells (P) regulate activity of mitral and tufted cells via presynaptic inhibition
  • axons of mitral and tufted cells = olfactory tract project to limbic system and cerebral cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

coding of olfactory stimuli:

A
  • each olfactory sensory neuron expresses only 1 odorant receptor gene/ protein -> only responds to 1 type of odorant (labelled lines)
  • found in specific locations
  • each glomerulus receives synaptic input from 1 type of olfactory neuron = responds to only 1 odorant
  • glomeruli arranged topographically - olfactory map in olfactory bulb
  • spatial organisation seemingly lost in primary olfactory (piriform) cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

coding of olfactory info:

A
  • most odours have different odorant molecules
  • stimulate multiple receptors - multiple olfactory sensory neurons - synapse w different glomeruli
  • discrimination from recognising spatial/ temporal patterns of glomerular activation
  • 10 000 different odours
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

neural pathways for olfaction:

A
  • axons of mitral/ tufted cells = olfactory tract
  • ipsilateral temporal lobe
  • piriform cortex
  • limbic system (amygdala)
  • entorhinal cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

neural pathways for olfaction: only sensory system that

A
  • whose pathway to main processing hub in cerebral cortex does not include synapse in thalamus (but olfactory info does go to thalamus)
  • cortical areas project to other limvic structures (hippocampus, hypothalamus, amygdala)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

neural pathways for olfactory info: piriform cortex

A
  • odour recognition

- olfactory learning/ memory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

neural pathways for olfactory info: limbic system

A

emotional and visceral responses to odours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

neural pathways for olfactory info: amygdala

A
  • olfactory hedonics

- olfactory recognition/ memory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

neural pathways for olfactory info: hippocampus

A
  • olfactory memory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

neural pathways for olfactory info: hypothalamus

A
  • emotional/ motivational responses to odours (sexual arousal)
  • visceral responses to odours (salivation, nausea, vomiting)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

neural pathways for olfactory info: entorhinal cortex

A
  • transfers info from cortex - hippocampus

- implicated in odour memory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

neural pathways for olfactory info: conscious awareness

A
  • orbitofrontal cortex (prefrontal cortex)

- olfactory input from piriform cortex via thalamus, olfactory/ gustatory/ visual stimuli are integrated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

gustation: features

A
  • chemoreception
  • tastants or certain chemicals in food react to chemoreceptors in mouth
  • receptors in taste buds
  • on tongue, roof, pharynx
  • those on palate/ pharynx more important for reflex to certain tastes (gagging/ vomiting)
23
Q

types of taste buds:

A
  • circumvallate papillae
  • fungiform
  • foliate
24
Q

taste buds: cicrumvallate

A
  • 8-12 in V shape at back of tongue

- each has 100-300

25
Q

taste buds: fungiform

A
  • mushroom shape
  • tip and sides of tongue
  • each have 5
26
Q

taste buds: foliate

A
  • 4/5 vertical fold on sides of tongue

- each have 100-150

27
Q

taste buds: gustatory calyculi

A
  • flask shaped
  • epithelial layer of tongue
  • each taste bud sits beneath small pore/ opening in epithelium
  • tastants enter pore contact microvilli at apical surface of gustatory receptors
  • taste buds innervated by afferent sensory fibres travel to gustatory areas of brain via CN VII, IX and X
28
Q

taste receptors: types

A

I to IV

29
Q

taste receptors: type I

A
  • support cell
  • degrade/ absorb NT
  • like astrocytes
30
Q

taste receptors: type II

A
  • receptor
  • gustatory receptors
  • NT ATP
  • sweet, bitter, umami
  • no clear synapse
31
Q

taste receptors: type III

A
  • presynaptic cells
  • gustatory receptors
  • synapse w afferent sensory fibres
  • may be excited by ATP
  • NT serotonin
  • sour, salty
32
Q

taste receptors: type IV

A
  • basal cells
  • immature cells
  • replace receptor cell
33
Q

taste: salty

A
  • chemical salts

- Na, sometimes Cl

34
Q

taste: sour

A

H+

35
Q

taste: sweet

A
  • ligands
  • sugars, glucose, fructose, maltose
  • glycols, alcohols, ketones
  • aa.
36
Q

taste: bitter

A
  • long organic substances w N and alkaloids

- typically toxic, avoided

37
Q

taste: umami

A

L glutamate

  • meat extracts
  • aging cheese
  • MSG
38
Q

salt path:

A
  • Na from salty good enter Na channel
  • depolarisation opens voltage gated Ca channels
  • influx of Ca causes NT release
39
Q

sour path:

A
  • H ions from sour foods block K channel
  • prevents K leaving cell
  • depolarisation opens voltage gated Ca channels
  • influx of Ca causes NT release
40
Q

sweet path:

A
  • sweet substance binds to receptor, conformational change
  • activates G protein -> adenylate cyclase
  • it catalyses conversion of ATP to cAMP
  • cAMP - kinase - phosphorylates - closes K channel
  • depolarisation - opens voltage gated Ca channels
  • influx of Ca - release of NT (ATP)
41
Q

sweet, bitter, umami path:

A
  • ligands bind to GPCRs and activate G proteins (gustducins)
  • produce 2ndary messenger (cAMP, IP3)
  • release stored Ca, depolarise via membrane cation channels
  • elevated [Ca]in opens large pores of gap junction hemichannels (Panx1)
  • ATP (NT) relased into extracellular space onto afferent nerve endings
42
Q

coding of taste: serotonin

A
  • from presynaptic cells (type III)

- excites sensory afferents, inhibit receptor cells (type II)

43
Q

coding of taste: ATP

A
  • released by receptor cells (type II)
  • excites sensory afferents
  • may also produce secondary excitation in presynaptic cells (type III)
44
Q

recordings show afferent sensory fibres show responses that either:

A
  • reflect narrowly tuned sensitivities of type II receptors
  • reflect broadly tuned sensitivities of type III presynaptic cells - respond to all taste sensations, preference for one sensation
45
Q

coding of taste: may deviate from

A
  • labelled line concept of sensory processing

- instead may be coded through patterns of spiking activity across population of receptor neurons

46
Q

neural pathway: taste

A
  • tongue, oesophagus and palate -> gustatory nucleus in nucleus of solitary tract in medulla
47
Q

neural pathway: taste CN VII

A
  • ant 2/3 of tongue
48
Q

neural pathway: taste CN IX

A

post 1/3 tongue, back of throat

- gag reflex

49
Q

neural pathway: taste CN X

A
  • root of tongue
  • epiglottis
  • palate
50
Q

neural pathway: taste 2nd and 3rd order neurons

A
  • 2nd order from medulla to ventral post complex of thalamus
  • 3rd order from thalamus to primary gustatory cortex in insular and frontal operculum
  • recipient areas close to mouth region of somatosensory cortex in parietal lobe
51
Q

info from different parts of tongue segregated in:

A
  • medulla
  • cortex
  • thalamus
  • cortex
52
Q

perception of flavour: complex combo of

A
  • chemical stimulation of taste buds - gustatory cortex
  • chemical stimulation of olfactory receptors - olfactory cortex
  • stimulation of somatosensory receptors in oral/ nasal cavities - info bout temp/ spiciness/ texture/ consistency via trigeminal n (CN V) to somatosensory cortex

incorporates:

  • visual- colour (visual cortex)
  • auditory- crispiness (auditory cortex)
53
Q

perception of flavour: orbitofrontal cortex

A

important role in integration of sensory info and perception of flavour
- OFC thought to compute ‘reward value’ to guide feeding behaviour (linked w reward system eg. NAc)

4. BIOL257 (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions