Final answer:
Stiffness and rigidity in Parkinson's disease are due to an increase in muscle tone, causing tightness and a reduced range of motion. These symptoms emerge from the loss of dopamine-producing neurons in the midbrain. Dopamine is essential for controlling movement, and its depletion leads to the various motor symptoms seen in Parkinson's patients.
Step-by-step explanation:
Stiffness and rigidity in Parkinson's disease refer to the increased muscle tone that leads to resistance to movement in the joints. The rigidity associated with Parkinson's can cause muscles to feel consistently tight and lead to a decreased range of motion.
This symptom is a result of the progressive degeneration of dopamine-producing neurons in the substantia nigra within the midbrain, crucial for regulating movement. The stiffness in Parkinson's contributes to difficulty with walking, postural changes, and can affect activities of daily living.
Parkinson's is characterized by four primary motor symptoms: tremor, muscle rigidity, bradykinesia (slowness of movement), and postural instability. Together with cognitive and emotional symptoms such as dementia and depression, these constitute the main features of the disease.
Loss of dopamine neurons in Parkinson's leads to these stiff, rigid muscles, and as the disease progresses, can lead to the classic slow, hunched walking posture observed in many patients.