2 Smell and Taste Flashcards
what is defined as the process which a sensory receptor is stimulated, producing nerve impulses (action potentials) that travel to the brain?
sensation
what occurs when the brain interprets impulses as a visual image, a sound, taste, odor, touch, or pain?
sensation
what is defined as a CNS process when the brain organizes the sensation and then begins the process of translation and interpretation
perception
what occurs when the brain processes information to give meaning to it, by means of identification, meanings, emotions, memories, etc.
perception
what is the preferred energy form of a receptor; its adequate stimulus
specific modality
what is the minimum stimulus needed to achieve an action potential
stimulus threshold
what is the physical location where sensory cells/neurons are activated
receptive fields
what is the activation of sensory receptor cells and their primary, or first order neurons (except sound)
coding stimulus locations
how does the brain localize sound
brain uses encoded APs timing/intensity differences from each ear to localize sound
what are the number of receptors activated and the frequency, or rate of action potentials (AP) per unit timie
coding stimulus inttensiity
what is the length of time that action potentials are generated, regardless of the frequency of APs
coding stimulus duration
what is a 1:1 association of receptor with sensation
labeled line coding
regardless of the stimulus, activating a particular ___ results in the sensation/perception that receptor’s adequate stimulus
labeled line
(bascially, when a particular population of neurons is active, the conscious perception is of a specific stimulus, regardless of the actual stimulus)
do labeled lines of the senses have a specific topographic projection to the cerebrum?
YES
what is a neuron(s) reduction and/or elimination of APs from neighboring neurons in a sensory neuron pathway
lateral inhibiition/inhibitory modulation
what enhances contrast and makes stimulus encoding more precise?
lateral inhibition/inhibitory modulation
what occurs when multiple receptors function together to encode quality, spatial, temporal characteristics of a stimulus
population coding
what type of coding is limited tto any single sensory system and not limited to a single sensory modality
population coding
what does the Chick-Fil-A example represent
population encoding of the 5 taste modalities to encode quality and hedonic value of complex tastant
___ continue to fire as long as the stimulus is maintained.
tonic receptors
___ monitor the presence and intensity of a stimulus
tonic receptors
___ respond to stimulus changes; they stop responding (e.g. APs) to a sustained stimulus
phasic receptors
what occurs when many sensory receptors give information (e.g. NTs) to a smaller number of neural cells? example?
neuronal convergence
e.g. olfactory neurons converging onto a single glomerulus
receptor type for smell
chemoreceptor
modality/ligand for smell
volatile, lipid soluble molecules:
Esters, terpenes, aromatics, amines (remember: give me the TEAA!!!)
embryonic origin of smell receptors
olfactory placode and neural crest
what neurons regenerate?
Olfactory neurons
No other neuron, where in PNS or CNS can regenerate
receptor type for taste
chemoreceptors
modalities/ligand for taste
water soluble molecules:
- sweet - sucrose, aspartame
- umami - glutamate
- bitter - quinine, phenylthiorea
- sour - H+
- salty - Na+
how do the taste receptors detect SWEETNESS
sucrose, aspartame
how do the taste receptors detect UMAMI
glutamate
how do the taste receptors detect BITTERNESS
quinine, phenylthiourea
how do the taste receptors detect SOURNESS
H+
how do the taste receptors detect SALTY
Na+
what is the embryonic origin for taste receptors
neuroepithelial
what neuron constantly regenerates due to short life but only if innervation to the neuron is maintained
taste receptors - the axons regeneratet
olfactory signal transduction cascade
- odor molecules bind to GPCR
- starts a signal transduction cascade that activates G-alpha protein (G olf), increasing adenylate cyclase activity and cAMP concentrations
- Cyclic Nucleotide Gated (CNG) cation channels are opened, causing an influx of Ca+ and Na+ charge into receptor neuron
- intracellular increase of + charge depolarizes olfactory neuron and generates APs (Ca2+ mediate Cl- eflux)
T/F: a single olfactory neuron only expresses a single GPCR
TRUE
while only 1/500 expresses a single GPCR, what happens to the other 499?
the other are repressed (chromatin remodeling) epigenetic changes)
all olfactory neurons that express the same GPCR will send axons where? this is an example of what?
to the same glomerulus in the olfactory bulb
e.g. of labeled line coding
what are the basic molecular, anatomical, developmental and functional unit for odor mapping and odor processing
glomeruli of the olfactory bulb
what helps create odor maps of encoded olfactory stimulation to account for discrimination of an estimated 1 trillion distinct odors in human olfaction
INHIBITOR MODULATION (e.g. lateral inhibition) in olfatory bulb
AND
population coding of individual LABELED LINES
taste buds contain what types of cells
Type I, II, and III taste cells
type II cell signal
- GPCR and G-alpha protein called GUSDUCIN for signal transduction
- different Na channel (compared to smell) activated by increased Ca2+ (Phospholipase c PLC and inositol triphosphate IP3)
- increased intracellular Ca2+ and cell depolarization activate GAP JUNCTION HEMICHANNELS allowing ATP to move out the cell (non-selective cation channel)
- ATP acts as a NT to generate APs in taste neuron
When ATP acts as a NT to generate AP in taste neurons, what type of signaling is this?
purinergic signaling (Type II taste cells)
what cell uses a different transduction mechanisms and synapses directly with taste neurons to generate action potentials? this is an example of what?
Type III taste cells - serotonergic signaling
taste info encoded in the AP of gustatory neurons include:
intensity, quality, hedonic value, and behavior
there is strong support for ___ of taste quality and behavior in less cerebral animals, despite the fact that neurophysiologic recordings of taste neurons (APs) support population coding of tastant stimuli
labeled line coding
how many olfactory nerve cell receptor proteins
~1000 GPCRs
what is the effect on cell receptor potential of olfactory nerve cells
depolarization
what is the effect on cell receptor potential of taste receptor cells
depolarization
what is the NT effect of olfactory nerve cells
INCREASE glutamate
what is the NT effect of taste receptor cells
INCREASE ATP
INCREASE SEROTONIN
ascending CNS pathway for smell
CN I -> olfactory bulb -> olfactory cortex -> (parallel) thalamus and limbic system (hypothalamus, hippocampus, amygdala)
ascending CNS pathway for taste
CN VII, IX, and X -> medulla (thru solitary tract nucleus) -> thalamus -> (parallel) gustatory cortex and limbic system
when the CNS pathways for smell and taste relay to the limbic system, sensory inputs are relayed to motor outputs in the form of what?
reflex arcs (e.g. salivary reflex)
