Lecture Week 2 Flashcards
What is Taste?
- Sensations evoked by solutions in the mouth
- They contact receptors on the tongue and roof of mouth
- Food breaks down into molecules and evoke sensation by activating taste buds
- Taste buds transduce those molecules into electrical energy
- We then perceive taste
Flavour
- We can distinguish between taste and flavour
- Flavour is the combination of true taste and retronasal olfaction
True Taste
- Sweet
- Sour
- Salty
- Bitter
Retronasal Olfaction
- The sense of smell
- Research says majority of flavour comes from smell system
Gustatory System
- Detects taste molecules we put into our mouths
- Molecules dissolved in saliva
- They then make contact with tastebuds and taste receptors
Retronasal Olfactory Sensation
- The sensation of an odour that is perceived when chewing and swallowing
- Odourant is forced into the mouth, behind the palate and to the nose
- Reach the olfactory epithelium
- The combination of activation of taste buds on tongue, olfactory epithelium gives us the flavour of the stimulus
Mozell et al., 1960
Without smell our ability to identify foods by taste alone is poor
Taste Buds
A cluster of cells that convey neural signals to the brain by taste nerves
Taste Receptor Cells
A cell within a taste bud that contains sites that can interact with charged particles and chemical structures
Types of Papillae
- Circumvallate Papillae
- Foliate Papillae
- Fungiform Papillae
- Shaped like mushrooms
- distributed along the edge of tongue
- mostly found on tip of tongue
- taste buds buried in surface
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Circumvallate Papillae
- Structures shaped like circles and mounds
- Formed in a V shape on the back of tongue
- Surrounded by trenches
- Taste buds buried in sides of trenches
Foliate Papillae
- Folds of tissue that contain taste buds
- Located on rear and sides of tongue
- Lateral to circumvalate papillae
Bogus Tongue Map
- Taste buds are found randomly on all parts of the tongue
- Different taste receptors responsible for different tastes are randomly disperesed
- There is no map of the tongue that indicates places that focus on certain tastes
Neural Pathway for Taste Perception
- After leaving taste buds, taste information travels through Medulla and Thalamus
- Information the travels to the Insular Cortex
- Then projects to the orbitofrontals Cortex
Insular Cortex
- The insular cortex links sensory experience and emotional valence
- Receives sensory information from the environment.
- Also known as Gustatory Cortex
- Projects to the Orbitofrontal Cortex
Nucleus of the Solitary Tract
- a series of purely sensory nuclei (clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata.
Taste - Orbitofrontal Cortex
- Where we have our conscious experience of flavour
- Where taste pleasure and displeasure is processed
Basic Tastes
- to be a basic taste the recpetor must be specific to that taste and respond only to that taste
- There must be an evolutionary basis for that taste
- Salty
- Sour
- Sweet
- Bitter
Basic Taste - Salty
- Produced by positive charged Salt Ions
- Evolutionary necesity: forour bodies to work we need a certain amount of salt in our body
- We crave salt when we have a salt deficiency
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Basic Taste - Sweet
- Taste quality naturally found in glucos, sucrose and fructose
- Preference for natural sweeteners because they are used for producing energy in us
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Basic Taste - Sour
- Produced by hydrogen ions in acids
- generally a disliked taste in large quantities
- Evoutionary Benefit: Large quantities of acids can damage our internal organs
- found to be preffered in small quantities
Basic Taste - Bitter
- Generally considered unpleasant in large quantities
- produced by substances such as quinine or caffeine
- Evolutionary Beneft: A lot of poisons are bitter, so it is useful to identify bitter tastes as unpleasant
Basic Taste - Umami
- Considered a ‘delicious savoury’ taste
- Produced by MSG to give a pure umami sensation
- Tends to be undetectable on its own - it needs sodium to make it palatable
- Combined with certain odours and saltiness leads to pleasant taste sensation
- Evolutionary Benefit - May indicate the prescence of proteins
- May require L-glutamate receptors and Receptors for amino acids
Anosmia
- Inability to smell
- Usually found in older people
- Olfactory processing with complex link to depression (Croy et al., 2014
Aguesia
- Inability to taste
- Usually found in older people also
- Taste dysfunction can lead to poor diet choices and may be related to obesity and well being
Supertasters
- The ability to detect Propylthiouracil (PROP)
- Hayes et al., 2008 found that both genotype and number of fungiform papillae contribute to being a supertaster
- about 1/3 population can taste and respond badly to PROP
- about 1/3 population cannot detect PROP
How many senses do we have.
- Aristotle described 5 major senses
- Touch
- Sight
- Sound
- Taste
- Smell
- There is also the sense of Equilibrium that is run by the Vestibular System
- Falling
- Acceleration
- Tilt
- Balance
Vestibluar System
- Organs and neural pathways that sense head motion, head orientation and orientation in gravity
- Often overlooked but very old evolutionarily
- Vestibular organs around the size of a pea
- Connected to the Cochlear
- Is an autonomic system
Vestibular organs help us by providing a sense of
- Linear Motion
- Angular Motion
- Tilt
Vestibulo-Ocular Reflex (VOR)
- Activation of the motoneurons that innervate the extra-ocular muscles.
- The function of these reflexes is to maintain the orientation of the eyes in space during head movements
- Assists the visual image remains stable on the retina.
Sense of Equilibrium
- Composed of multiple reflexes and perceptual Modalities
- Visual Stability
- Balance
- Autonomic Nervous System
- regulates oBlood Pressure when we stand
- Spatial Orientation
- Begins in Vestibular Organs in inner ear
Sense of Proprioception
- Sense of where your body is in space
Spatial Orientation
- Sense of where your head in relation to gravity
- consists of three interacting modalities
- Linear Motion
- Angular Motion
- Tilt
Sense of Linear Motion
- Going forward and back and side to side
Sense of Angular Motion
- Rotation of the head
Sense of Tilt
- Leaning left and right, forward and back
Three Directions for Sense of Rotation:
Roll
Rotation around the x-axis