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Chemical senses Flashcards

1
Q

Physical senses

A

The actual source of the stimulus is far away, and does not enter our body (vision, audition, touch)

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2
Q

Chemical senses

A

Direct interaction between source of information and sensory organs allowing us to perceive the composition of our chemical environment (information enters our body)

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3
Q

List of chemical senses

A

Taste (gustation), Smell (olfaction), Trigeminal system

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4
Q

Taste

A

We perceive taste stimuli via the interaction between soluble substances with gustatory receptors located in taste buds of the tongue (and elsewhere in the oral cavity).

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5
Q

5 taste qualities we can distinguish with taste receptors

A
  • sweet
  • sour
  • salty
  • bitter
  • umami
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6
Q

Taste buds are located on the ______ of the tongue (and elsewhere in the oral cavity).

A

Mucosa

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7
Q

Taste buds are found in the ______

A

Papillae

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8
Q

How do the taste buds initiate taste perception ?

A

The saliva will get in the taste buds, where the receptors respond to the taste substances in the saliva : there will be a depolarization in those cells, and the electrical signal will travel to the brain where it will become conscious that we taste something.

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9
Q

Types of papillae

A
  • fungiform papillae
  • foliate papillae
  • circumvallate papillae : at the back of the tongue
  • (filiform papillae) : in () because have nothing to do with taste, responsible for somatosensory perception from the tongue
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10
Q

The papillae are the _____ on the tongue : they are found on the front, on the side and the back.

A

Bumps

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11
Q

The taste map

A

The taste map is an urban legend:
- We can taste all qualities everywhere on the tongue

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12
Q

The main central pathway of information goes from the taste buds on the tongue to the brain stem through the 3 …

A

cranial nerves

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13
Q

The two anterior thirds of the tongue are connected with the brain stem via …

A

cranial nerve 7 (facial nerve)

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14
Q

The taste buds on the posterior third of the tongue are connected with the brain stem via …

A

cranial nerve 9 (grosopharyngeal)

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15
Q

The taste buds on the epiglottis with the brain stem via …

A

cranial nerve 10, the vagus nerve

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16
Q

All the taste buds are ultimately connected to this same structure in the brainstem

A

solitary nucleus of the brainstem.

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17
Q

Pathway of taste

A
  1. From the solitary nucleus of the brain stem
  2. first synapse to the thalamus
  3. primary gustatory cortex in the insula and inferior parietal cortex, where we have processing of gustatory information
    - Some connections go from the brainstem solitary nucleus to the hypothalamus and to the amygdala
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18
Q

We perceive smells via olfactory receptors located in the …

A

olfactory mucosa in the upper portion of the nasal cavity.

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19
Q

How many odors can we distinguish between ?

A

millions

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20
Q

Olfactory stimuli are ______ substances. To perceive them, the odorants have to be released by the odor source, enter our body and get into contact with the olfactory receptor cells in the upper portion of the nasal cavity.

A

Volatile

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21
Q

In the upper portion of the nasal cavity is the olfactory mucosa where we find …

A

Axons of the olfactory receptor cells that together form the olfactory nerve, the cranial nerve 1 . They are sensory cells that are exposed to the outside world, unlike cells for physical senses.

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22
Q

Septum

A

What separates the 2 nostrils
- Goes on inside the nose, creating two distinct nasal cavities.
- The 2 nasal cavities are only connected at the pharynx.
- The nasal septum is often deviated to one side.

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23
Q

Vomeronasal organ

A

on the septal side of the nasal cavity, plays a role in the effect of pheromones

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24
Q

Turbinates

A

help us heat up, humidify and clean the air that goes in the nose

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25
Olfactory receptor neurons (ORN) are situated in...
The roof portion of the nasal cavity. The receptors are located in their cilia.
26
ORN are surrounded by ...
supporting cells and can regenerate from stem cells.
27
Olfactory receptors are on hair cells. How do the hair cells work ?
The hair cells are exposed to the outside air. When the air transports odorants, the air goes over the hair cells. The odorants get in contact with the olfactory receptors. The cells will send an electrical signal to the brain and we will smell something.
28
Bone separates nasal cavity from the brain. On top of this bone, we have the ...
epithelium tissue mucosa.
29
We have ____ times more olfactory receptors than receptors in the visual system.
100 (2% of our genetic information is responsible for encoding olfactory receptors)
30
We humans have approximately ___ different types of olfactory receptors
400
31
Does each odor receptor respond to one smell ?
No - Each receptor does not respond to a single odorant : rather they respond to some physical chemical characteristics of the odor molecules, e.g. the presence of a sulfur atom in the odorant
32
Each olfactory receptor neuron (ORN) in the olfactory mucosa carries ___ type(s) of receptor.
1
33
Each ORN can be activated by ...
Different substances because activated not by a particular substance, but the physical chemical property
34
Each substance can activate different types of _____
ORN * Nearly infinite combinations possible : why we can distinguish up to a trillion of odors * Each individual has a different olfactory receptor repertoire.
35
The amount of olfactory receptors is ______ from person to person
Variable E.g. someone with 400 receptors can smell odors that someone with 380 cannot. - the olfactory world smells different for everybody
36
Why does cilantro taste like soap for some people ?
They have a specific olfactory receptor that makes them more sensitive to cilantro : smells like soap; those without this receptor only perceive cilantro with other receptors
37
Pathway of odor perception
1. The axon of the first ORN in the olfactory mucosa pass through the cribriform plate of the ethmoid bone and reach the olfactory bulb : where the olfactory nerve enters the brain or the central nervous system. 2. The second neuron in the olfactory bulb sends its Axon to the primary olfactory processing areas : the information is in the cortex.
38
Olfactory bulb
first structure to be entered (part of the brain) by odor information, where the first synapse is
39
Axons of all olfactory neurons carrying one type of receptor converge to one ______ within the olfactory bulb.
Glomerulum
40
Olfactory tract
axons that form the synapse from the olfactory bulb to the orbitofrontal cortex
41
Primary olfactory cortex contains...
* Piriform cortex * Amygdala * Entorhinal cortex - hippocampus also receives direct input from the olfactory bulb.
42
Secondary olfactory cortex contains...
* Orbitofrontal cortex * Insula
43
Differences between olfactory system and other sensory systems
In the olfactory system contrary to the other sensory systems : 1. No crossing over of the fibers. 2. No mandatory relay in the thalamus 3. Only 2 neurons until the information enters the cortex 4. The regions of olfactory processing have other tasks beside olfaction
44
No crossing over of the fibers in the olfactory system
- Most of the processing processing takes place ipsilaterally. - What enters the right nostril is processed in the right hemisphere.
45
No mandatory relay in the thalamus in the olfactory system
- In all other sensory systems, the info. travels to the thalamus before the cortex - In the olfactory system, the info. travels directly to the cortex
46
Only 2 neurons until the information enters the cortex in the olfactory system
- 3 or more neurons for other sensory systems In olfactory system : - The first neuron axon in the olfactory mucosa goes to olfactory bulb for a synapse - The second neuron sends its Axon to the primary olfactory processing areas : the information is in the cortex.
47
The regions of olfactory processing have other tasks beside olfaction
In the olfactory system, the regions for olfactory processing also belong to the limbic system - the entorhinal cortex and the hippocampus are responsible for the creation of new memories, and learning - Amygdala : responsible for emotions, especially negative ones - Orbitofrontal cortex : reward
48
Orthonasal perception
When an odor source close to me gets into my nose, gets in contact with the olfactory mucosa and I perceive it
49
Retronasal perception
- The odor source is not outside our body, outside our nose, but it's inside our body. - E.g. when we have food in our month - When I pinch my nose, the air here cannot enter the nasal cavity from the back because this is closed : no retronasal perception - When i release my nose, there is a difference : an additional perception
50
Retronasal perception allows us to distinguish...
between an apple and a pineapple for example - People without a sense of smell lose the fine taste qualities, like the distinction between apple and pineapple
51
Volatile substances are released from the odor source and reach the olfactory cleft, within the respiration air stream
orthonasal smelling
52
Volatile substances are released from the odor source and reach the olfactory cleft, during swallowing
Retronasal smelling
53
Why does sniffing (orthonasal smelling) increase the smell perception ?
When we breathe vigorously, more air gets into our nostril, higher speed turbulences are created and much more of the olfactory molecules will reach the proportion of the nasal cavity, allowing us to smell something we not smell with normal breathing.
54
Why does slurping (retronasl smelling) increase the smell perception ?
- When we have something in our mouth, the odorants can enter the nasal cavity while I'm chewing and so on - But I can increase the amount of odorants by slurping : I move my tongue and my palate, creating turbulences in my mouth. By doing so, much more of these odorants will get into the nasal cavity and I will be able to perceive odorants that I'm not able to perceive usually.
55
Warning function of smell
**Microbial threats** - E.g. when something is rotten * disgust **Non-microbial threats** - E.g. smoke * fear Note :smell cannot wake you up
56
Nutrition function of smell
* detection and identification (useful for our ancestors) * expectancy violation : e.g. a banana that smells like a kiwi indicates not to eat it * intake regulation : when hungry, everything smells good : then pleasantness goes down as we continue eating until we are sated * breastfeeding
57
(Social) communication function of smell
We all have a body odor - We perceive them unconsciously : play a role in how we encounter others * reproduction * incest avoidance : body odor of someone genetically too closes to you is perceived as less attractive * fitness evaluation in potential partners : some body odors are linked to diseases * Emotional contagion : body odor of people who parachuted for the first time was collected, then had to rate threatening level of a picture : when they were exposed to the fear sweat, they rated those faces as more threatening than when they were exposed to exercise sweat.
58
Up to __% of the population suffer from olfactory dysfunction.
20
59
Anosmia (quantitative dysfunction)
Complete loss of olfactory function. * 5% of the population
60
Hyposmia (quantitative dysfunction)
* Partial loss of olfactory function. * 15% of population
61
Parosmia (qualitative dysfunction)
odors are perceived differently than they are supposed to. E.g. vanilla will smell like burnt rubber With retronasal olfaction : - What tastes vanilla will taste like burnt rubber. * 30% of patients with hyposmia
62
Phantosmia (qualitative dysfunction)
Perception of smells, typically unpleasant, in the absence of an odor source (not hallucination). * Relatively rare
63
Results of testing people who report loss of smell and taste
Only 20% usually report smell issue, but an objective evaluation shows that more than 2/3 do actually have a smell problem, and approximately 2% have indeed a taste problem. - So even if people complain about their sense of taste, in most cases it's a smell problem.
64
Diseases of the nose or the nasal mucosa as cause of olfactory dysfunction
25-50% of olfactory dysfunction * Chronic sinusitis * Polyps * Allergies * (Common cold)
65
Neurological diseases as cause of olfactory dysfunction
15-35% of olfactory dysfunction * Traumatic brain injury : When you have a concussion, little fibers that connect the nose with the brain can be severed * Alzheimer’s : 90-95% have a smell problem that predates the diagnosis 10-15 years * Parkinson’s : same as Alzheimer * Congenital anosmia : born without being able to smell due to no olfactory bulb
66
Unknown cause of olfactory dysfunction
15-35% of olfactory dysfunction * Olfactory dysfunction following upper respiratory tract infection. * Idiopathic olfactory dysfunction
67
Age and olfactory dysfunction
Sense of smell gets worse with age
68
Olfactory dysfunction is a marker for COVID-19 because ...
There is a very strong reduction of the olfactory abilities (up to 60%) in the very early phases of COVID
69
Factors that influence olfaction
* Age (younger better than older) * Sex (female better than male) * Education level (more years of schooling) * Smoking (former smokers) * Alcohol consumption (moderate drinkers better than abstainers) * BMI (normal better than obese) * Blood pressure (normal better than stage II) * Traumatic Brain Injury (skull fracture) * Positive screening for Parkinson’s * Positive screening for dementia
70
Consequences of olfactory dysfunction
Danger * spoiled food * gas, smoke, fire Professional * chef * electrician * sommelier, etc. Quality of life * eating and drinking * personal hygiene * life as a couple * depression
71
trigeminal system (chemesthesis)
third chemosensory system next to smell and taste.
72
receptors of the trigeminal system are located on...
fibers of the trigeminal nerve (cranial nerve 5) of the nasal and oral mucosa (innervates the oral and nasal cavity)
73
trigeminal stimuli (chemical substances) evoke sensations such as
* irritation * burning * freshness * tingling * etc.
74
Trigeminal stimuli is nominally ______ of smell and taste
Independent However, there is still a lot of interaction between the different chemical chemosensory systems : Usually, the three chemical senses work together. Flavor perception is the result of the integration of input from the different chemical senses.

Perception (16 decks)

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