Olfaction

• Olfactory receptors are responsible for the sense of smell by detecting odors via the olfactory hairs containing chemoreceptors. They are found within the olfactory epithelium in the upper part of the nasal cavity (10-100 million)
• Odorants are the chemicals that cause odor and stimulate olfactory hairs. Humans have the ability to recognize around 10 000 odors.
• Adaptation to odors occurs rapidly (around first second after stimulation)
• The axons of olfactory receptors extend to the olfactory bulb. Neurons of the olfactory bulb then project to the temporal lobe of the cerebral cortex, which is when the conscious awareness of smell begins
• Signals sent from the olfactory bulb also enter the limbic system and hypothalamus which is why certain odors can evoke emotional responses or memories
• Hyposmia: reduced ability to smell. It is often caused by age or by neurological problems such as Alzheimer’s or certain drugs or smoking