1. S PECIAL S ENSES : S MELL Jenna Balderson Kaijaii Gomez Wick Linh Nguyen Sunny Xu

2. W HAT IS SMELL ? Smell is perception of chemicals in the air through olfactory nerves and organs. The olfactory cortex and neurons are part of the limbic system, which directs and processes emotion and feeling. Smell is closely associated with memory and is important in the formation of memories.

3. S ENSORY O RGANS AND S TRUCTURES ASSOCIATED WITH S MELL The nose is the sensory organ responsible for smell. The cavities of the nose are lined with mucus membranes that are connected to the olfactory nerve. Smell reflexes are located in the hypothalamus. The olfactory cortex, which receives sensory input, is located in the temporal lobe. The olfactory bulb processes the information about odors.

4. D IAGRAM 1

5. D IAGRAM 2

6. S PECIFIC S ENSORY R ECEPTORS Smell depends on sensory receptors. In humans, chemoreceptors are located in the olfactory epithelium. The olfactory epithelium is patch of tissue located in the nasal cavity, on the surface of the mucous membrane. Olfactory receptor cells are neurons with olfactory hairs (long cilia that stick out from the nasal epithelium and are coated in mucus). They are stimulated when chemicals dissolve in the mucus.

7. P ATHWAY TO THE B RAIN 1. Olfactory receptors (neurons with cilia) on the mucous membrane of the nasal cavity react to chemical stimuli 2. They send the impulse up the olfactory filaments, through the cribiform plate of the ethmoid bone, to the olfactory neurons (mitral cells) 3. The neurons, whose axons are bundled together into the olfactory nerve (cranial nerve I), send the impulse to the olfactory bulbs (grey matter of olfactory neurons) 4. They transmit the impulse along the olfactory tract to the olfactory cortex (white matter of the olfactory bulbs) 5. The olfactory cortex processes and integrates the information into smell perception

8. P ATHWAY TO THE B RAIN D IAGRAM

9. D ISORDERS Hyperosmia: To have the ability to smell and perceive odors greater than the average person. Smells become heightened. This disorder arises when there is an abnormally increased signal at any point between the receptors and the cortex of the olfactory system. Olfactory hallucinations: The phenomenon of smelling odors that are not actually present. It results from damage to the nervous tissue of the olfactory system- confused neurons along the sensory system pathway.