The gustatory system or sense of taste is the sensory system that is partially responsible for the perception of taste (flavor). Taste is the perception stimulated when a substance in the mouth reacts chemically with taste receptor cells located on taste buds in the oral cavity, mostly on the tongue. Taste, along with the sense of smell and trigeminal nerve stimulation (registering texture, pain, and temperature), determines flavors of food and other substances. Humans have taste receptors on taste buds and other areas, including the upper surface of the tongue and the epiglottis. The gustatory cortex is responsible for the perception of taste. The tongue is covered with thousands of small bumps called papillae, which are visible to the naked eye. Within each papilla are hundreds of taste buds. The exception to this is the filiform papillae that do not contain taste buds. There are between 2000 and 5000 taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. Each taste bud contains 50 to 100 taste receptor cells. Taste receptors in the...

Parkinson's disease (PD), or simply Parkinson's, is a chronic degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms become more common. Early symptoms are tremor, rigidity, slowness of movement, and difficulty with walking. Problems may also arise with cognition, behaviour, sleep, and sensory systems. Parkinson's disease dementia becomes common in advanced stages of the disease. The motor symptoms of the disease result from the death of nerve cells in the substantia nigra, a region of the midbrain that supplies dopamine to the basal ganglia. The cause of this cell death is poorly understood, but involves the aggregation of the protein alpha-synuclein into Lewy bodies within the neurons. Collectively, the main motor symptoms are known as parkinsonism or a parkinsonian syndrome.The cause of PD is unknown, but a combination of genetic and environmental factors are believed to play a role. Those with an affected family member are at an increased risk of getting the disease, with certain genes known to be...