Olfaction - Chapter 30

Question 1

Describe the path from an olfactory sensory neuron to cortex:

Answer 1

Olfactory neuron in the olfactory epithelium sends projections to a glomerulus region of the olfactory bulb that has extensive synapses with Mitral, Tufted and interneurons. Processing occurs here and mitral cells project directly to cortex. Each glomerulus is connected by periglomerular cells (when 1 glomerulus is activated the neighboring glomeruli are inhibited). Cortical projection neurons are connected by granule cells.

Question 2

How does an odorant lead to neural activity?

Answer 2

Olfactory Sensory Neurons express ~350 types of receptors. A molecule that binds to one of these receptors causes a G-Protein signalling cascade.
- G-Protein subunits separate and binds GTP. The subunit activates adenylyl cyclase which converts ATP into cAMP. This opens cAMP gated channels which allows Na+ and Ca2+ entry into the cell (depolarization). Ca2+ entry opens Ca2+ gated channels.