Neurotransmitters
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Transcript of Neurotransmitters
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Neurotransmitters
Ca++ K+ Na+
Where a venom (or drug) could work. . .
Receptor Agonists / AntagonistsReuptake Inhibitors
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The first neuron was probably a chemo-receptor. . .
‘Taste’ is sensing a chemical in a liquid phase‘Olfaction’ is sensing a chemical in a gas phase
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A Cellular Understanding of Taste
We eat for our cells What do cells need? Well. . . What are cells doing?
Amino Acids (to build proteins, enzymes)
Carbohydrates (cellular energy) Some Basic Elements (salts, metals) Enzyme Co-factors (vitamins)
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Obvious Biological Importance
Where’s FAT in all this?
What do we perceive as taste?Bitter, Sour, Salt, Sweet, and Umami. . . And then we ‘feel’
Approach vs. Avoidance Do you think these two will be equal?
Is this learned?
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Resting dH2O Sweet Sour Bitter
Examples of the characteristic facial expressive features in response to gustatory stimulation (gustofacial reflex) in
the perinatal human infant (Steiner 1987).
Evidence That Taste Is Innate
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Examples of the gustofacial reflex in normal and abnormal perinatal infants and in normal, blind, and severely learning-disabled adolescents (Steiner 1987).
Resting face
Sweet
Sour
Bitter
Normal An-encephalic
Hydro-anencephalic
Normal Blind LearningDisabled
Neonates Adolescents
Reflex is Controlled by Brainstem Structures
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2D Receptor Arrays
Rat’s tongue viewed from the side. Lopez & Krimm, 2006
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Looking down on a rat’s tongue. Lopez & Krimm, 2006
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Taste BudStructure
Important Features:
Taste Pore
Microvilli
Tight Junctions
Nerve Fibers to Brain
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‘Labeled-Line’ receptors for Taste
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Overlap in the distribution of receptors for the 5 basic tastes (however, thresholds for
each differ)
Bitter Salty Sweet Umami Sour
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Individual taste buds typically contain
receptor cells for each class of taste
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Transduction: 2 of the ‘basic tastes’ rely on ‘second
messenger’ systems, as does Umami
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Transduction: 2 of the basic tastes rely on ‘second messenger’
systems, as does Umami
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2nd Messenger Systems:G-Protein Coupled
Receptors
The end result is similar to ‘1st Messenger’ systems
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Effect of Temperature on Thresholds
The lower the threshold, the greater the perceived taste or sensitivity.
Important features:• Sweet Range• Sour sensitivity• Bitter sensitivity
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Vagus Nerve
Regions of the tongue are innervated by specific sensory taste nerves.
GlossopharyngealNerve
Chorda Tympani Nerve (something familiar here. . .)
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Neural Pathways
Note: No Left/Right Crossing
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Brain regions receiving taste information
2. AMYGDALAConditioned Taste Aversions
1. Primary Gustatory Cortex - Perception of taste quality (bitter, sour, salty, sweet, umami)
3. Hypothalamus - Hunger and satietyH
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Primary Gustatory Cortex: Gustotopic Mapping
Cortical Field Sensitive to Bitter
Chen et al. 2011
1:1
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Neural Pathways: Orbitofrontal Cortex
Note: No Left/Right Crossing
Many:1
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National Geographic, 1985
Compared to Taste, Olfaction seems to be mostly learned. . .
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Olfactory Stimuli
Must be volatileThink of things that have taste but no smell . . . and vice versa
Similar to Taste in FunctionApproach/Avoidance – but LEARNEDRetronasal OlfactionAdditional ‘Social’ Role (pheromones)
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Three ‘Olfactory’ Systems
The Main Olfactory SystemMain Olfactory BulbWhat we think of as ‘smell’
The Vomeronasal SystemAccessory Olfactory BulbPheromonal Signals
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University of Washington. 1997.
Mid-saggital View in Human
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Some Drawbacks in Design
Olfactory Receptors and SomeNeurons in the Bulb also Regenerate
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Olfactory ReceptorsAre G-Protein Coupled
Receptors
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Model for olfactory coding
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Optical Imaging of Odorant
Representations in the
Mammalian Olfactory Bulb
Odorants with similar
molecular structures
activate similar sets of
glomeruli
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Marchand et al., 2003
Relationships Among Response Patterns and Receptor Distributions
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Projections of the Main Olfactory System
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Projections of the Accessory Olfactory System
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The Accessory Olfactory System• Pheromones (may be volatile or soluble)• Role in mammalian social behavior, endocrine function• The Vomeronasal organ - Accessory Olfactory Bulb• Primary output of AOS to Amygdala, Hypothalamus• Do humans have a VNO?
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Pheromones
Used by most mammals, many insects to communicate: Sex (and reproductive status) Lineage Individuality
Modest positive evidence for a role in humans McClintock Effect – which is not a behavioral effect
Humans use Visual and Auditory cues to signal SLI Emphasis on the head and face Skin, hair, eyes, other facial features, voice
The reduced importance of pheromonal signaling in humans has implications for understanding our behavior
Why sex is not a strictly ‘reproductive’ behavior in humans Why sexual attraction in humans is complex Why there are ‘races’ of humans, and what ‘race’ means