Chapter 10 - Taste + Smell

Chemosensation

• chemoreceptors: respond to chemical stimuli

• taste/gustation

• smell/oflaction

Taste bud

• comprised of 50-100 specialized epithelial cells called TASTE CELLS that undergo APS and synapse with sensory neurons

• taste cells → transduce chemicals

Salty

Na+ through ion channel → depolarization → opens Ca2+ channels → neurotransmitter released → sensory neuron stimulated

Sour

H+ through ion channel (and other effects) → opens Ca2+ channels → neurotransmitter released → sensory neuron stimulated

Sweet + Umami

binds to membrane receptors for sweet + umami → sugar or amino acids → G-protein → second messenger → Close K+ channels → depolarization → NT → sensory neuron stimulated

Bitter

Binds to membrane receptor → Quinine → G-proteins → second messenger → Ca2+ released from endoplasmic → NT → sensory neuron activated

Olfaction Process

1. Odorants → stimulate olfactory sensory neurons (bipolar) by binding to membrane receptors (proteins in the cilia of olfactory sensory neurons)

2. axons of sensory neurons synapse onto olfactory bulb of brain

3. olfactory tract (grouping of axons) carries AFFERENT information from bulb to other brain areas for perception to occur

   • 10,000 odors are coded by variations in binding of odorants to 380 different membrane receptors → unique patterns of activity that brain interprets to perceive an odor