Lecture 22 Flashcards
Audition
Pressure waves hit the eardrum and later hair cells in the inner ear
Vision
Photons hit rods and cones of the retina
Touch
Pressure and vibration act on sensory cells of the skin
Physical Senses
-Audition
-Vision
-Touch
The Chemical Senses
-Tase, gustation
-Smell, olfaction
-Trigeminal system
Taste
Perceived via the interaction between soluble substances with gustatory receptors located in taste buds of the tongue (and elsewhere in the oral cavaity)
-Sweet
-Sour
-Salty
-Bitter
-Umami
5 Taste Qualities
Smell
-Perceived via olfactory receptors located in the olfactory mucosa in the upper portion of the nsala cavity
-We can distinguish between millions of different odors
-Olfactory stimuli are volatile substances
-In order for us to perceive a substance, the odor molecules have to be released and interact with my olfactory receptors (body)
Trigeminal System
A third chemosensory system next to smell and taste. Its receptors are located on fibers of the trigeminal nerve of the nasal and oral mucosa
Sensations evoked by Trigeminal system
-Irritation
-Burning
-Freshness
-Tingling
Flavour Perception
The result of the integration of input from the different chemical senses
Sour and Bitter
These tastes are often confused
-Lemon
-Orange
-Grapefruit
-Vinegar
-Coffee
Umami
Taste of (sodium) glutamate
-Was described as a tase enhancer, but it is an independent taste quality
-Meat
-Cheese
-Tomato
-Mushrooms
Taste Buds
Located on the mucosa of the tongue (and elsewhere in the oral cavity)
-Found in the papillae of the tongue
Fungiform Papillae
Found on the tip of the tongue, scattered amongst the filiform papillae but are mostly present on the tip and sides of the tongue
Foliate Papillae
Small sized vertical folds located on the tongue’s posterolateral sides, just anterior to the palatoglossal arch of fauces
Circumvallate Papillae
7-11 of these are located on the backside of your tongue, containing over 100 taste buds each
Filiform Papillae
Fine, small, cone-shaped papillae found on the anterior surface of the tongue. They are responsible for giving the tongue its texture and are responsible for the sensation of touch
True
The taste map is an urban legend. We can tase all qualities everywhere on the tongue.
TRUE OR FALSE
Central Pathway of Taste
- Enters brainstem via cranial nerves
- Goes to ventral posterior medial (VPM) of thalamus
- Spreads to hypothalamus + amydala
- Finishes in insula + parietal cortex
olfaction
Important to understand the nose to understand…
the nostrils
-E.g. to enter church, must go through the doors
To go to the nose, must go through…
-Narrow
-Bigger
-E.g. once you enter the church doors, big space insiden
-Nostril opening is ______, but goes far back + high up
-Behind the nostrils is a ______ space + receptors
2
-Huge wall inside that divides church in half
Inside the nose we have ____ nasal cavities seperated from each other
deviated septum
A-symmetry between nostrils = ?
Inside the Nose
-Narrow
-Very sensitive
-Olfactory cleft –> upper nose
Olfactory Receptor Neurons (ORN)
-Situated in roof portion of the nasal cavity
-Located in their cilia
-Surround by supporting cells and can regenerate from stem cells
The Olfactory Code
-app. 400 different types of receptors
1. Each olfactory receptor neuron (ORN) carries only one type of receptor
2. Each ORN can be activated by different substances
3. Each substance can activate different types of ORN
-Nearly infinite combinations possible
-Each individual has a different olfactory receptor repertoire
-E.g. people who smell silantro as ‘‘soapy’’ vs. others who don’t
Macroscopic Structures
Axons of the ORN pass through the cibriform plate of the ethmoid bone and reach the olfactory bulb
All the axons converge to the same spot
Axons of all olfactory neurons carrying one type of receptor converge to one glomerulum within the olfactory bulb
Primary Olfactory Cortex
-Piriform cortex
-Amygdala
-Entorhinal cortex
Secondary Olfactory Cortex
-Orbitofrontal cortex
-Insula
in the right hemisphere
What comes from the right nostril is processed…
0 thalamus relay
Direct to cortex = ?
These brain structures don’t just have 1 function
This is why a smell can bring you back to a specific memory
Orthonasal Olfaction
The perception of odors which occurs during sniffing
-Respiration air stream
-Sniffing can cause turbulence, therefor more molecules reach the olfactory musoca
Retronasal Olfaction
The perception of odors emanating from the oral cavity during eating and drinking
-During swallowing
-Slurping can cause turbulence, therefor more molecules reach the olfactory musoca
-In class demo with jelly-bean**
Smell Functions
- Warning
- Nutrition
- (Social) Communication
Smell Function: Warning
-Microbial threats (disgust)
-Non-microbial threats (fear)
-Smell will not wake you up while you are sleeping, only when it becomes very dense –> at this point detection is too late = fire alarms
Smell Function: Nutrition
-Detection and identification
-Expectancy violation (expected something - tasted something else)
-Intake Regulation
-Breastfeeding
Smell Function: (Social) Communication
Reproduction
-incest avoidance
-fitness evaluation in potential partners
-body odours that are genetically close to you are perceived as unattractive
-sick (fever) = more unpleasant body odour
Emotional Contagion
-What we smell (e.g. fear body odour) influences what we perceive
Olfactory Dysfunction
-Quantitative dysfunctiom
-Qualitative dysfunction
Quantitative Dysfunction
Anosmia
-complete loss of olfactory function
-5% of the population
Hyposmia
-partial loss of olfactory function
-15% of population
Qualitative Dysfunction
Parosmia
-odors are perceived differently than they are supposed to
-30% of patients with hyposmia
-doesn’t smell right
Phantosmia
-perception of smells in the absence of an odor source
-relatively rare
-constantly have a bad smell in their nose
Assessment
In many cases individuals with olfactory dysfunction think to suffer from problems with their sense of taste
-Complain about not being able to taste –> it’s actually the loss of smell
Main Causes of Olfactory Dysfunction
- Diseases of the nose or nasal mucosa
- Neurological disease
- Unknown
- Age
Nasal Mucosa
25-50% of olfactory dysfunction
-chronic sinusitis
-polyps
-allergies
-common cold
Neurological Disease
15-35% of olfactory dysfunction
-traumatic brain injury
-alzheimer’s (10-15 years before diagnosis, loss sense of smell/reduction)
-parkinson’s
-congenital anosmia
Unknown
15-35% of olfactory dysfunction
-olfactory dysfunction following upper respiratory tract infection
-idiopathic olfactory dysfunction
Aging
Half of people aged 65-80 years
-Three quarters of people over 80 years old have an olfactory disorder
Factors that Influence Olfaction
-younger better than older
-female better than male
-more years of schooling
-former smokers
-moderate drinkers better than abstainers
-normal better than obese
-normal better than stage II
-traumatic brain injury
-positive screening for Parkinson’s
-positive screening for dementia
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
Recovery
-Relatively high rate of (spontaneous) recovery
-increase in olfactory function can be observed even after long refractory periods
-training further improves function
