exam 2: Lecture 20 Chemical sense (smell and taste) Flashcards
what are the chemical senses?
taste and smell
how does smell work?
cilia on the bottom of the mucosal layer send the signal to the dendrites of the olfactory sensory neuron and then their axons go to the olfactory bulb
- the olfactory bulb projects to the olfactory cortex and this projects to the orbitofrontal cortex
what do odor receptors respond to?
only 1 type of molecule
- molecules may trigger many different receptors at one time
how many odorant receptors do humans have?
only 400
- each type receptor is confined to confined to certain regions of the nasal epithelium
what is the bone that the axons of the nasal cavity project through?
the cribriform plate
glomeruli?
tangled bits of dendrites of relay neurons in the olfactory bulb which project to olfactory relay neurons going to the olfactory cortex
olfactory relay neurons do what?
relay smell information to primary olfactory cortex right above the eyes and then the orbitofrontal cortex just behind primary olfactory cortex
- examples are turfed and mitral cells
how many glomeruli are there in the olfactory bulb?
800 because there are 2 glomeruli for every odor receptor in the nasal epithelium
what 2 places does the olfactory bulb project to?
- the olfactory cortex project to orbitofrontal cortex just above the eyes and allows odor discrimination in humans
- project to lateral hypothalamus involved with appetite
pheromones
special class of odorants that can modulate levels of reproductive hormones
- Can elicit aggression or sexual behavior
- Often found in urine or glandular secretions
- not yet clear if humans have this
general anosmia
inability to smell
2 types of general anosmia?
traumatic from a blow to the head or transient from respiratory infections
specific anosmia
inability to smell specific odorants
- common and genetic
5 taste senses
- Sweet
- Umami ⇒ flavor of amino acids
- Salty
- Sour
- Bitter
what taste senses are appealing and not appealing to people?
appealing: sweet and umami
aversive: sour and bitter
taste
results from the activation of the 5 receptors
flavor
complex sensation resulting from the mixing of taste with smell and somatosensation
what 3 cranial nerves are involved with taste?
- facial CN7 => anterior 2/3
- glossopharyngeal CN9 => posterior 1/3
- Vagus CN 10 ==> epiglottis and posterior oropharynx
papillae and 3 types?
where most of the taste buds are located
- circumvallate
- foliate
- fungiform
circumvallate taste buds
on the very back of your tongue relating to glossopharyngeal nerve
foliate taste buds
on the posterior lateral part of your tongue relating to facial nerve
fungiform taste buds
on the lateral middle and front of your tongue relating to the facial nerve
what are taste buds innervated by?
gustatory afferent neurons have their terminal innervating the base of the tastebud
- leading to only one of the 3 cranial nerves
what do taste receptors act like?
they act like neurons and can have action potentials + release a neurotransmitter onto the terminal of the nerves
what do T1 receptors relate to?
sweet and umami taste receptors
- these are a dimer with 2 proteins in them
what do T2 receptors relate to?
bitter taste receptors
what taste senses have gated ion channels for either sodium or sodium and hydrogen?
salt (Na+) and sour (Na+; H+)
what kind of receptors do fungiform papillae have?
T1 receptors for umami taste
what kind of receptors do circumvallate papillae have?
T1 receptors for sweet taste
what kind of receptors do foliate papillae have?
T2 receptors for bitter taste
does taste project contralateral or ipsilateral?
ipsilateral and everything else is contralateral
what tract do taste sensations enter and where?
they enter the solitary tract in the rostral medulla
what is the pathway for taste to the brain?
receptor –> solitary tract –> ventral posterior medial thalamus –> gustatory cortex (insula)
ageusia and partial ageusia
loss of sense of taste and loss of a particular taste
dyspepsia
constant unpleasant metallic taste in mouth
how does loss of taste occur?
from damage to chorda tympani; branch of the facial nerve responsible for taste in anterior tongue
