Olfactory, Gustatory

1
Olfactory, Gustatory

• Objectives For each sense identify
• specialized organs, anatomy
• receptor structure and specializations
• receptor signal transduction mechanism
• coding of intensity and duration
• pathway of conduction to the CNS

2
Olfaction

• Sense organs nose olfactory epithelium
• Receptor type neuron w/ memb. G-proteins
• Receptor signal transduction mechanism
• Coding of intensity and duration
• Pathway of conduction to the CNS
• Coding for perceived sensation - receptors are
  specific for only a few smells

3
Olfaction Sense organs nose olfactory
epithelium
Olfactory area in humans is about 2.5 cm2 w/
approx. 5 million sensory receptor
cells. Recognize thousands of odors.
4
Neuronal receptor synapses with CN I - goes to
olfactory cortex in medial temporal lobe
5
Receptor neuron w/ membrane G-proteins
Olfactory receptors are specific to a few
molecules G-proteins - bind one or a class of
molecules cAMP is second messenger in some
receptors .leading to Na channel opening
6
citrus
moldy
wet grass

• The receptors are located randomly in the
  epithelium, each neuron has its own type of
  receptor

But their axons cluster by receptor type (thus,
by odor) in the olfactory bulb
7
Gustation - the sense of taste

• Sense organs tongue throat, taste buds
• Receptor type non-neuronal

8
Transduction Each taste has a specific mechanism
to depolarize cell, ?ICF Ca2, release NT Salty
Na influx Sour H, block K Bitter
G-proteinIP3 Sweet G-protein cAMP, block K
9

• Taste path
• CN VII (facial)
• CN IX (glph.)
• CN X (vagus)
• ? medulla
• thalamus
• gustatory cortex