Final answer:
Orofacial manifestations of Parkinson's disease typically include a mask-like expression, difficulty swallowing, and increased salivation, but not tremors, which are a general motor symptom. The disease is characterized by the loss of dopamine-secreting neurons.
Step-by-step explanation:
The orofacial manifestations of Parkinson's disease include a mask-like facial expression, difficulty swallowing (dysphagia), and increased salivation. These symptoms reflect the neuromuscular impairments caused by the disease. However, tremors, while a common motor symptom of Parkinson's disease, are not considered an orofacial manifestation. As for the neurochemical basis of Parkinson's disease, it is primarily associated with the degeneration of neurons that release dopamine, leading to the classic symptoms such as muscle tremor, rigidity, and postural instability.