chemosensory systems Flashcards
3 chemical senses
olfactory (smell)
gustatory (taste)
trigeminal (chemosensory irritant)
olfaction
information about the identity, concentration and quality of odorants
pathway of olfaction
olfactory epithelium -> olfactory bulb -> to CNS via olfactory tract
odors can evoke responses such as
- salivation
- gagging/vomiting
- mother/infant bonding
- infant recognition of mothers
- synchronized menstrual cycles
vomeronasal system
a separate, parallel system for detecting odorants (pheromones)
- in rodents and predators
- involved in sexual, reproductive, and aggressive responses
olfactory receptor neurons (ORN)
have protruding cilia that have receptors for odorants
bowman’s gland
makes mucus for protection
transduction of olfactory info occurs in the
olfactory epithelium
olfactory transduction
- receptors bind to receptor protein
- changes conformation, thus activating an olfactory specific G-protein
- activates adenyl cyclase III
- increase cAMP
- opens cation channels
- Ca2+ increases
- Ca2+ opens Ca2+ gated Cl- channels (causes depolarization)
- ORN depolarize
taste buds
primary preceptors of taste located in epithelial specializations on the tongue, soft palate, pharynx, and esophagus
taste pathway
taste buds -> solitary tract -> hypothalamus (homeostasis) and thalamus -> gustatory cortex (insula and frontal cortex) -> amygdala (reward/pain memory)
5 categories of taste
sour
bitter
salty
sweet
MSG (umami)
taste action potential
apical part of taste cells have receptors for different tastants
these change the membrane potential in a graded way, and change release of transmitter in a graded fashion
sufficient conc leads to generation of action potentials in post-synaptic cell
salt
directly opens ion channels
Na+
sour
acids
directly open ion channels
H+
sweet
receptors are G-protein coupled
T1R2, T1R3
umami
amino acids
receptors are G-protein coupled
T1R1, T1R3, IP3, Ca2+
bitter
uses a different set of G-protein coupled receptors
T2R, IP3, Ca2+
supertasters
people with heightened sense of taste
- have heightened acuity, particularly for bitter
trigeminal system
comprised of nociceptive neurons that sense temp and irritation such as
- air pollutants
- ammonia
- ethanol
- acetic acid
- capsaicin
nociceptive neurons trigger physiological respones
salivation
tearing
nasal secretion
sweating
decreased respiratory rate
