The<unk> , or olfaction, is the special sense through which<unk> s (or odors) are perceived. The<unk>  has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans it occurs when an odor binds to a receptor within the nasal cavity, transmitting a signal through the olfactory system. Glomeruli aggregate signals from these receptors and transmit them to the olfactory bulb, where the sensory input will start to interact with parts of the brain responsible for<unk>  identification, memory, and emotion. There are many different causes for alteration, lack, or disturbance to a normal<unk> , and can include damage to the nose or<unk>  receptors, or central problems affecting the brain. Some causes include upper respiratory infections, traumatic brain injury, and neurodegenerative disease.
Sense of smell
Affective sensation
Visual perception
Sense of balance
Sensory phenomena
Pain tolerance
Sensation 
Color vision