Final answer:
Abnormal movement can result from an imbalance in neurotransmitters affecting brain regions that control motion, as seen in Parkinson's disease, involving the death of dopamine-producing neurons. This leads to disruptions in direct and indirect neuronal pathways and presents as movement disorders which can be tested through motor exams.
Step-by-step explanation:
Abnormal movement is often a direct result of an abnormally low level of a neurotransmitter affecting the parts of the brain that control movement. Conditions like Parkinson's disease illustrate the consequences of such neurological impairments. In Parkinson's, neurons in the substantia nigra pars compacta die, leading to decreased dopamine release in the striatum. This disrupts the balance between the direct and indirect pathways in the basal nuclei, often causing hypokinetic disorders, such as Parkinson's disease, which are characterized by decreased movement and muscle rigidity.
The motor exam can reveal the presence of movement disorders through the inspection of muscle tone and structure, as well as the assessment of passive range of motion. Abnormal findings such as hypotonicity or flaccidity may indicate that the lower motor neurons (LMN) are not conducting action potentials, affecting the release of neurotransmitters like acetylcholine at neuromuscular junctions.
Parkinson's disease has both primary and secondary forms, with the former being the most common without a known cause and the latter associated with known or suspected causes such as exposure to toxins or repeated head trauma. An inherited gene coding for an abnormal protein can also lead to the death of neurons, contributing to the onset of movement disorders.