Lecture Week 2 Flashcards

1
Q

What is Taste?

A
  • 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
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2
Q

Flavour

A
  • We can distinguish between taste and flavour
  • Flavour is the combination of true taste and retronasal olfaction
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3
Q

True Taste

A
  • Sweet
  • Sour
  • Salty
  • Bitter
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4
Q

Retronasal Olfaction

A
  • The sense of smell
  • Research says majority of flavour comes from smell system
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5
Q

Gustatory System

A
  • Detects taste molecules we put into our mouths
  • Molecules dissolved in saliva
  • They then make contact with tastebuds and taste receptors
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6
Q

Retronasal Olfactory Sensation

A
  • 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
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7
Q

Mozell et al., 1960

A

Without smell our ability to identify foods by taste alone is poor

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8
Q

Taste Buds

A

A cluster of cells that convey neural signals to the brain by taste nerves

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9
Q

Taste Receptor Cells

A

A cell within a taste bud that contains sites that can interact with charged particles and chemical structures

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10
Q

Types of Papillae

A
  1. Circumvallate Papillae
  2. Foliate Papillae
  3. Fungiform Papillae
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11
Q
  • Shaped like mushrooms
  • distributed along the edge of tongue
  • mostly found on tip of tongue
  • taste buds buried in surface
    *
A
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12
Q

Circumvallate Papillae

A
  • 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
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13
Q

Foliate Papillae

A
  • Folds of tissue that contain taste buds
  • Located on rear and sides of tongue
  • Lateral to circumvalate papillae
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14
Q

Bogus Tongue Map

A
  • 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
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15
Q

Neural Pathway for Taste Perception

A
  1. After leaving taste buds, taste information travels through Medulla and Thalamus
  2. Information the travels to the Insular Cortex
  3. Then projects to the orbitofrontals Cortex
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16
Q

Insular Cortex

A
  • 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
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17
Q

Nucleus of the Solitary Tract

A
  • a series of purely sensory nuclei (clusters of nerve cell bodies) forming a vertical column of grey matter embedded in the medulla oblongata.
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18
Q

Taste - Orbitofrontal Cortex

A
  • Where we have our conscious experience of flavour
  • Where taste pleasure and displeasure is processed
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19
Q

Basic Tastes

A
  • 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
  1. Salty
  2. Sour
  3. Sweet
  4. Bitter
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20
Q

Basic Taste - Salty

A
  • 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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21
Q

Basic Taste - Sweet

A
  • 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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22
Q

Basic Taste - Sour

A
  • 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
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23
Q

Basic Taste - Bitter

A
  • 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
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24
Q

Basic Taste - Umami

A
  • 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
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25
Q

Anosmia

A
  • Inability to smell
  • Usually found in older people
  • Olfactory processing with complex link to depression (Croy et al., 2014
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26
Q

Aguesia

A
  • 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
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27
Q

Supertasters

A
  • 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
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28
Q

How many senses do we have.

A
  • Aristotle described 5 major senses
    1. Touch
    2. Sight
    3. Sound
    4. Taste
    5. Smell
  • There is also the sense of Equilibrium that is run by the Vestibular System
    • Falling
    • Acceleration
    • Tilt
    • Balance
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29
Q

Vestibluar System

A
  • 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
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30
Q

Vestibular organs help us by providing a sense of

A
  1. Linear Motion
  2. Angular Motion
  3. Tilt
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31
Q

Vestibulo-Ocular Reflex (VOR)

A
  • 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.
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32
Q

Sense of Equilibrium

A
  • 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
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33
Q

Sense of Proprioception

A
  • Sense of where your body is in space
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34
Q

Spatial Orientation

A
  • Sense of where your head in relation to gravity
  • consists of three interacting modalities
    • Linear Motion
    • Angular Motion
    • Tilt
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35
Q

Sense of Linear Motion

A
  • Going forward and back and side to side
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36
Q

Sense of Angular Motion

A
  • Rotation of the head
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37
Q

Sense of Tilt

A
  • Leaning left and right, forward and back
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38
Q

Three Directions for Sense of Rotation:

Roll

A

Rotation around the x-axis

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39
Q

Three Directions for Sense of Rotation:

Pitch

A

Rotation around the y-axis

40
Q

Three Directions for Sense of Rotation:

Yaw

A

Rotation around the z-axis

41
Q

Stereocilia

A
  • Hair cells that transduce mechanical stimulus in inner ear and send neural activity to the brain
  • Depending on the directions of movement it will move towards the largest hair in the cell or away from it
  • It will then depolarise increasing action potential or hyperpolarise decreasing action potential
42
Q

The Five Vestibular Organs

A
  1. Semicicular Canals
    • Respond to pitch yaw and roll
  2. Otolith Organs
    • Utricule
    • Saccule
43
Q

Semicircular Canals

A
  • Three tubes in vestibular system that sense angulare acceleration
  • Sense of angular motion “head spinning” in pitch, yaw and roll
  • Each canal is sensitive to each type of rotation
44
Q

The Vestibular Push-Pull Relationship

A
  • We have two sets of Vestibular Organs one in each ear
  • Movement in one direction will polarise stereocilia in one ear and hyperpolarise them in another
  • this type of pattern of hyperpolarisation and depolarisation that gives us sensation of movement
45
Q

What is endolymph?

A

the fluid contained in the membranous labyrinth of the inner ear

46
Q

Neural Activity in Semicircular Canals

A
  • Neural activity in these canals are senstive to change in rotation velocity
  • constant rotation leads to decreased responding from the stereocilia after a few seconds
  • We sense the acceleration in the movement of a car but then do not sense that we are moving unless there is a sudden brake or change in the level of accelaration
47
Q

Otolith Organs

A
  • Sense linear velocity
  • where the endolymph from the canals end up
  • contain stereocilia
    • Utricle has 30,000 hair cells
    • Saccule has 16,000 hair cells
  • Semicircular
48
Q

Utricula Macula

A
  • Responsible for detecting movement along horizontal plane; forward and back, left and right
  • eg: walking, running, driving
49
Q

Saccular Macula

A
  • Responsible for detecting vertical movement
  • sky diving, falling, landing in a plane
50
Q

Otolith Organs - Anatomy (8)

A
  • Striola
  • Otoconia
  • Otolithic Membrane
  • Gelatinous layer
  • Reticular Membrane
  • Supporting Cells
  • Hair cells
  • Afferent Neurons
51
Q

Otoconia

A
  • calcium carbonate crystals that sit on top of the otolithic membrane
  • they shift around and this movements shifts the hair cells
  • they then either polarise or depolarise whcihc tells us the change in movement
  • watch Video in Week 2 Lecture 1:10:00 mins
52
Q

Striolia

A
  • a narrow curved zone that divide each macula in two areas:
    • Saccule
    • Utricle
  • It is observable in all mammalians.
53
Q

Otolithic Membrane

A
  • a fibrous structure located in the vestibular system of the inner ear
  • Plays a critical role in the brain’s interpretation of equilibrium.
  • Serves to determine if the body or the head is tilted
  • Also serves to perceive the linear acceleration of the body.
54
Q

Gelatinous Layer

A
  • Overlying the hair cells and their hair bundles is a gelatinous layer
  • Above that layer is the otolithic membrane
55
Q

Reticular Membrane

A
  • In the ear
  • A stiff membrane that forms a division between endolymph and perilymph
  • Some of the hair cells of the stereocilia make contact with the reticular membrane.
56
Q

Hair Cells

A

The sensory cells within the inner ear that transduce mechanical displacement into neural impulses.

57
Q

Afferent Neurons

A
  • Also known as sensory neurons or afferent nerve fibers
  • Pathways that carry sensory information from the body to the central nervous system
  • From the sense organs to the brain and spinal cord
58
Q

3 Experimentational techniques used to examine spatial orientation

A
  • Threshold Estimation
  • Magnitude estimation
  • Cross Modality Matching
59
Q

Threshold Estimation

A
  • What is the minimum motion needed to correctly perceive motion?
60
Q

Magnitude Estimation

A
  • Participants report how much or how many degrees they have tilted rotated or translated in linear motion
61
Q

Cross Modality Matching

A
  • Participants are tilted and then orient a line with the direction of gravity.
62
Q

Rotation Perception

A
  • Tested in the dark
  • Generally people can tell if they spin in clockwise or anti clockwise direction
  • They soon feel like they are slowing down even though the rotation is constant
  • After a short time they no longer feel like they are rotating at all
  • Upon stopping they feel like they are spinning in the opposite direction
63
Q

Vestibular response

A
  • Only respond to changes for 20-30 seconds
  • After this it normalises again until there is another change
  • If endolymph is not changing then the current position is perceived as normal
64
Q

Translation Perception

A
  • People can reproduce the velocity and direction of a linear trajectory even if they have been translated in the dark
65
Q

Tilt Perception

A
  • People can reproduce the angle of movement if they have been tilted in the dark
66
Q

Sensory Integration

A
  • The ability to combine several senses together to more accurately perceive our environment.
  • Visual and Vestibular senses combine strongly to give sense of where we are oriented
67
Q

Vection

A
  • The illusion that we are moving when we are in fact still
    eg: non moving escalators, train moving next to your own train
68
Q

Visual-Vestibular Integration

A

Visual and Vestibular senses combine strongly to give sense of where we are oriented

69
Q

What happens when the vestibular system fails

A
  • Spatial disorientation
  • Imbalance
  • Distorted vision unless head is perfectly still
  • Motion sickness
  • Cognitive problems
70
Q

Meniere’s Syndrome

A
  • Sever sudden dizziness, imbalance, spatial disorientation
  • Can cause sudden falling
  • Unpredictable and terrifying
71
Q

Vestibular Function - Gurvich et al., 2013

A

Common neural pathways for vestibular function and many psychiatric disorders

72
Q

Vestibular Function – Staab 2016

A

30-50% of patients with vestibular disorders have a co-existing psychiatric disorder such as anxiety, depression, PTSD, OCD

73
Q

Vestibular Function – Smith et al., 2016

A
  • Vestibular system influences higher order cognitive processing including working memory, spatial memory, attention and executive function
74
Q

Vestibular Function – Smith & Darlington, 2013

A
  • Personality can be affected by vestibular disturbances
  • Patients with vestibular dysfunction report depersonalisation & derealisation
  • This indicates vestibular system makes a key contribution to the sense of self.
75
Q

Why do we need a sense of touch

A
  • Detect damage
  • Detect disease and maintain homeostasis
  • Sense temperature changes
  • Determine body position and where our muscles are moving
  • Feeling deformities
  • Sustained pressure on our skin
  • Detect low and high frequency changes
76
Q

Touch Receptor Physiology

A
  • Touch receptors found in the Dermis and Epidermis
  • Grouped by:
    • Type of stimulation receptor responds to
      • Mechanorecepters
      • Olfactory sensory neurons
    • Size of receptive field
    • Rate of adaptation
77
Q

Receptor Fields

A
  • Each receptor cell will synapse to a single neuron
  • Each Neuron receives messages from multiple receptors
  • Neurons don’t differentiate which receptor it receives information from
  • Activation is activation from a many receptors which then synapse to one neuron
78
Q

Rate of Adaption – Fast Adapting

A
  • Responds when pressure is first applied
  • Responds again when pressure is taken off
79
Q

Rate of Adaptation – Slow Adapting

A

Fires continuously when pressure is applied to the skin

80
Q

Tactile Sensations

A
  • All mechanical displacement
  • Picking things up or touching things
  • Tactile Mechanoreceptors
81
Q

Kinesthetic Mechanoreceptors

A
  • Located in ligaments, muscles and bones
  • Tell us position of our body and limbs in space
82
Q

Thermoreceptors

A
  • Sense changes in temperature
  • Both Heat and Cold receptors
  • Regulate body temperature to assist in Homeostasis
83
Q

Nociceptors

A
  • Pain Receptors
  • Synapse whenever they detect damage to the body tissue.

Eg: when pin is pressed to skin mechanoreceptors fire but if pressure continues to pierce skin nociceptors begin to respond

84
Q

Kinesthesia

A

Perception of the movement of our limbs in space

85
Q

Proprioception

A

Perception of the position of our limbs in space

86
Q

Somatosensation

A
  • Sensory signals from the skin muscles tendons, joints and internal receptors
  • All sensory receptors and perception combine together to create a sense of Somatosensation
  • Different types of receptors can send messages via the same kinds of channels
87
Q

Mechanoreceptors – Meissner Corpuscle

A
  • In the Epidermis
  • Generally found in hairless skin
  • Fast Adapting type 1
88
Q

Meissner Corpuscle

A

Hand Grip Control

89
Q

Mechanoreceptors - Merkel Cells

A
  • In the Epidermis
  • Generally found in hairless skin
  • Slowly adapting type 1
90
Q

Merkel Cells

A
  • Fires to continous pressure
  • Fine details
91
Q

Mechanoreceptors - Ruffini Endings

A
  • Located in the Dermis
  • Generally found in hairless skin
  • Slowly Adapting Type II
92
Q

Ruffini Endings

A
  • Fires to continuous pressure
  • Responsible for stretching muscles
  • Large Receptive fields
93
Q

Mechanoreceptor - Pacinian Corpuscle

A
  • Located in the Dermis
  • Generally found in hairless skin
  • Fast Adapting Type II
94
Q

Pacinian Corpuscle

A
  • Large Receptive Fields
  • Fires to On and Off
  • Responsible for perceiving vibration and finetwxture by moving fingers
95
Q

Kinesthetic Receptors

A

Mechanoreceptors in muscles, tendons and joints

96
Q

Muscle Spindles

A
  • Mostly perceive angles and tension of limbs
  • lenght of the change of the spindle that tells our brain that the muscle is moving in a certain way
97
Q

Range of response for Thermoreceptors

A
  • Respond when we make contact with objects warmer than 36o
  • Respond to objects colder than 30o
  • This helps to keep the body in homeostasis
  • respond to Heat, Cold, pressure and chemicals