Smell

1. Olfaction is the sense of smell.
2. Olfactory neuron receptor molecules are responsible for the detection of odor molecules. Activation of these receptors is the initial player in a signal transduction cascade which ultimately produces a nerve impulse which is transmitted to the brain.
   
   

   Human olfactory system. 1: Olfactory bulb 2: Mitral cells 3: Bone 4: Nasal epithelium 5: Glomerulus 6: Olfactory receptor neurons.

   
   
3. Located on the inferior side of the brain, the olfactory bulb is the primary neural structure of the vertebrate forebrain involved in olfaction, or the sense of smell.
   
   

   Head anatomy showing olfactory nerve and olfactory bulb.

4. The olfactory tract is a bundle of axons connecting the mitral and tufted cells of the olfactory bulb to several target regions in the brain.