PSYC2274 Chapter Notes - Chapter 15: Lingual Papilla, Chorda Tympani, Olfactory Mucosa
1
- What makes tongues “smile”? MOLECULES!
- Taste serves the most specific function of any of the senses: discerning which chemicals
we need to ingest because they are nutritious, and which we need to spit out because they
may be poisonous.
TASTE VERSUS FLAVOR
- Tastes → sensations evoked by solutions in the mouth that contact receptors on the
tongue and the roof of the mouth than then connect to axons in cranial nerves VII,
IX, and X.
- Retronasal olfactory sensations → sensation of an odor perceived when chewing and
swallowing force an odorant in the mouth up behind the palate into the nose.
- Perceived as originating from the mouth, even though the actual contact of
odorant and receptor occurs at the olfactory mucosa.
- Brain combines retronasal olfactory sensations with taste sensations into flavor →
combination of true taste (sweet, salty, sour, and bitter) and retronasal olfaction.
- Retronasal olfactory input enhances the taste of sweet.
LOCALIZING FLAVOR SENSATIONS
- We perceive flavor as comin entirely from our mouth…this is in part due to tactile
sensations evoked by chewing and swallowing, and in part to taste.
- Chorda tympani → branch of cranial nerve VII (facial nerve) that carries taste info
from anterior mobile tongue.
- Exits tongue with lingual branch of trigeminal nerve (cranial nerve V) and then
passes through the middle ear on its way to the brain.
- Cranial nerves → 12 pairs of nerves (one for each side of body) that originate in brain
stem and reach sense organs and muscles through openings in the skull.
- The brain processes odors differently, depending on whether they come from the mouth
or through the nostrils.
ANATOMY AND PHYSIOLOGY OF THE GUSTATORY SYSTEM
- Chewing breaks down food substances into molecules.
- Molecules are dissolved in saliva.
- Saliva-born food molecules flow into a taste pore → leads to the taste buds housed in
papillae.
- Taste buds contain multiple taste receptor cells (can interact with taste stimuli) which
responds to a limited number of molecule types.
- When comes into contact with preferred molecules, taste receptor cell produces
APs that send info along one of the cranial nerves to the brain.
find more resources at oneclass.com
find more resources at oneclass.com
2
- Tongue is the retina of the mouth!
PAPILLAE
- Give tongue its bumpy appearance and come in 4 major varieties:
Filiform papillae
- Without taste function! Located on anterior portion of tongue and come in different
shapes in the different species.
Fungiform papillae
- Mushroom-shaped structures that are distributed most densely on edges of tongue,
especially the tip. Taste buds are buried in the surface at an avg. of 6 per papilla.
Foliate papillae
- Located on sides of tongue where it attaches to the mouth and look like a series of folds.
Taste buds are buried in the folds.
Circumvallate papillae
- Large, circular structures that form an inverted V on rear of tongue. Mound-like
structures, each surrounded by a trench (like a moat). Much larger than fungiform
papillae. Taste buds are buried in sides of the moats.
So…
- Taste buds are distributed in a line across roof of mouth and in papillae distributed in an
oval on the tongue.
TASTE BUDS AND TASTE RECEPTOR CELLS
- Each taste bud is a cluster of elongated cells organized much like segments of an orange.
- Tips of some cells end in slender microvilli containing sites that bind to taste substances.
- Microvilli are extensions of the cell membrane.
- Taste bud cells communicate with each other within the taste bud.
- Fall into 3 different groups:
- Type I cells → housekeeping cells. Excrete potassium and allow other cell
types to maintain their resting membrane potential. Also play role in salt taste.
- Type II cells → true receptor cells that respond to only one of sweet, bitter, or
umami stimuli. Have G protein-coupled receptors (GPCRs) but do not have
synapses.
- Type III cells → now called presynaptic cells and have synapses. May also
play a role in sour taste.
- Overall message: different tastants excite different taste bud cells utilizing different
transmitters.
- Taste receptors have limited life spans.
- Constant renewal enables taste system to recover from a variety of sources of damage and
explains why taste systems remain robust even into old age.
find more resources at oneclass.com
find more resources at oneclass.com
