Lecture 6 : Chemoreception, auditory and vestibular physiology
auditory : https://www.youtube.com/watch?v=1JE8WduJKV4, https://www.youtube.com/watch?v=46aNGGNPm7s
vestibular : https://www.youtube.com/watch?v=mTbn73JRoLM, https://www.youtube.com/watch?v=uCRx5pr1n2I
chemoreception taste :
Chemoreception
Taste (Gustation) -dep smell (Olfaction) - dep
receptor ● modified epithelium cells ● neurons, bipolar neurons (nasal epith)
● taste buds (live about 2 W) ○ only n to come in contact w external
envi
○ 1st order neurons of the olfactory
pathway
○ Basal stem cell → new olfactory
receptor
● Cells of the olfactory mucosa
○ olfact recptor
■ bipolar n w cilia/ olfact hair
○ supporting cells
○ basal cells
○ olfactory glands (Browmann)
○ receptor cells
○ basal cells
○ receptor cells
○ sensory afferent axon
○ microvilli that project into taste pore
● Taste cells synapse w primary sensory axons
Taste ● sweet, sour, salty, bitter, umami (glutamate) ● odorants bind to receptors
Transduct° ● ● Na+/ Ca2+/ Cl- channel open
● Depolarization occurs
salty/ sour sweet/ bitter/umami ● Nerve impulse is triggered
ion channel 2nd messenger
Ca2+ → vesicle Ca2+ → / vesicle → ATP
mechanism → serotonin
1. The odorant binds to a specific olfactory receptor
protein in the cell membrane of a cilium of an
olfactory receptor cell.
2. Receptor activation stimulates a heterotrimeric G
protein (Golf).
3. The α subunit of Golf activates adenylyl cyclase III
(ACIII) → cAMP.
4. The cAMP binds to a cyclic nucleotide – gated
● Each taste cell makes synaptic contact w a different (CNG) cation channel
1
, primary gustatory axon leads into CNS → gustatory 5. Opening of this channel increases permeability to
discrimination Na+, K+, and Ca2+.
● pathway 6. The net inward current leads to membrane
depolarization and increased [Ca2+]i
1. stimuls
7. The increased [Ca2+]i opens Ca2+ → activated
2. Cl− channels called anoctamin2 (ANO2) →more
n. taste bud depolarization (especially because of the relatively
high [Cl−]i of olfactory receptor neurons).
8. If the receptor potential exceeds the threshold, it
facial n (VII) ant triggers action potentials in the soma that travel
down the axon and into the brain.
glossophary n (IX) circumvallate + post ⅓
vagus n (X) epiglottis
3. solitary nc
4. medial lemniscus
5. Thalamus → insula
● Olfactory receptor axons terminate on the
dendrites of mitral cells (2nd order olfactory
neurons), in a restricted encapsulated strc
called glomerulus
○ 1 mitral cell → 1 odorant = primary
basis of olfactory coding
● Olfactory pathway :
○
2
auditory : https://www.youtube.com/watch?v=1JE8WduJKV4, https://www.youtube.com/watch?v=46aNGGNPm7s
vestibular : https://www.youtube.com/watch?v=mTbn73JRoLM, https://www.youtube.com/watch?v=uCRx5pr1n2I
chemoreception taste :
Chemoreception
Taste (Gustation) -dep smell (Olfaction) - dep
receptor ● modified epithelium cells ● neurons, bipolar neurons (nasal epith)
● taste buds (live about 2 W) ○ only n to come in contact w external
envi
○ 1st order neurons of the olfactory
pathway
○ Basal stem cell → new olfactory
receptor
● Cells of the olfactory mucosa
○ olfact recptor
■ bipolar n w cilia/ olfact hair
○ supporting cells
○ basal cells
○ olfactory glands (Browmann)
○ receptor cells
○ basal cells
○ receptor cells
○ sensory afferent axon
○ microvilli that project into taste pore
● Taste cells synapse w primary sensory axons
Taste ● sweet, sour, salty, bitter, umami (glutamate) ● odorants bind to receptors
Transduct° ● ● Na+/ Ca2+/ Cl- channel open
● Depolarization occurs
salty/ sour sweet/ bitter/umami ● Nerve impulse is triggered
ion channel 2nd messenger
Ca2+ → vesicle Ca2+ → / vesicle → ATP
mechanism → serotonin
1. The odorant binds to a specific olfactory receptor
protein in the cell membrane of a cilium of an
olfactory receptor cell.
2. Receptor activation stimulates a heterotrimeric G
protein (Golf).
3. The α subunit of Golf activates adenylyl cyclase III
(ACIII) → cAMP.
4. The cAMP binds to a cyclic nucleotide – gated
● Each taste cell makes synaptic contact w a different (CNG) cation channel
1
, primary gustatory axon leads into CNS → gustatory 5. Opening of this channel increases permeability to
discrimination Na+, K+, and Ca2+.
● pathway 6. The net inward current leads to membrane
depolarization and increased [Ca2+]i
1. stimuls
7. The increased [Ca2+]i opens Ca2+ → activated
2. Cl− channels called anoctamin2 (ANO2) →more
n. taste bud depolarization (especially because of the relatively
high [Cl−]i of olfactory receptor neurons).
8. If the receptor potential exceeds the threshold, it
facial n (VII) ant triggers action potentials in the soma that travel
down the axon and into the brain.
glossophary n (IX) circumvallate + post ⅓
vagus n (X) epiglottis
3. solitary nc
4. medial lemniscus
5. Thalamus → insula
● Olfactory receptor axons terminate on the
dendrites of mitral cells (2nd order olfactory
neurons), in a restricted encapsulated strc
called glomerulus
○ 1 mitral cell → 1 odorant = primary
basis of olfactory coding
● Olfactory pathway :
○
2
