chemical senses Flashcards
uses of chemo senses
identify things that should be consumed for survival
detect things that could be harmful
causes good and bad emotional responses
gustation
structure and function of taste
4 types of papilla
filiform
funigofrm
foliate
circumvallate
filiform papilla
shaped like cones
located over entire surface
no taste buds
only for structure
fungiform papilla
shaped like mushrooms
found on sides and tip of tongue
foliate papilla
series of fold on back and sides
circumvallate
shaped like flat mounds in a trench
located at the back
taste buds
tongue contains around 10,000
each has 50-100 tase receptor cells with tips that extend into the taste pore
transaction occurs when chemical contact the receptor sites on the tips of the taste cell
- sent to brain by an afferent axon
areas of the tongue
tongue isn’t category specific
different areas don’t deter different tastes
all buds have same receptors on them
but some may have different sensitivities
nerves in the tongue
3 different nerves pick up signals from different areas
vagus nerve - back of tongue
glossopharyngeal nerve - further back
facial nerve - tip of tongue
neural pathway from tongue to cortex
signals from 3 nerves converge to solitary nucleus in brain stem
related to the thalamus
goes into primary gustatory cortex (insula)
signal passed to secondary gustatory cortex (frontal operculum)
pick up information from tongue
- different nerves from different areas
generates an action potential
olfaction
structure and function of odour
olfactory mucosa
membrane that contains the cilia of the olfactory receptors
where the receptors are found
pick up molecules from the air
where transduction occurs
olfactory bulb
goes to olfactory bulb from mucosa
structure containing the neural circuits that process olfactory information
neurons recieven information directly from the axons of the olfactory receptors
functions of olfaction
macrosmatic olfaction
- many animals
- keen sense of smell, necessary for survival
microsmatic olfaction
- present in humans
- less keen, not crucial
detecting odours - sensitivity
different species have different sensitivities to odours
however individual receptors are all equally sensitive
- difference lies in number of receptors
identifying odours - recognition
recognition threshold is the concentration needed to determine quality of an operant
humans can discriminate among many odours but cannot label them correctly
not caused by a lack of sensitivity
puzzle of olfactory quality
difficult to map perceptual experience onto physical attributes
some molecules that have similar structures smell different
some molecules that have different structures smell the same
neural pathways from nose to cortex
information from olfactory bulb passed to piriform cortex (primary olfactory cortex)
passed to orbitofrontal cortex (secondary)
all link to the amygdala
- related to emotions and fight or flight response
flavour
combination of smell, taste and other sensations
odour stimuli from food in the mouth reach the olfactory mucosa through the retronasal route
- taste of many compounds influenced by olfaction
smell gives 80% of flavour
only 20% from gustation
flavour effected by
smell
taste
context
appearance
texture
physiological state
temperature
mood state
beliefs - religion, diets, past experience
2 pathways to brain in flavour
orthonasal
- not chewed, only in nasal cavity
retronasal
- molecules come into mouth and onto tongue
- nasal and oral cavity connected by nasal pharynx
- air flows through both absorbed by olfactory mucosa
