Jeremy has Parkinson's disease a progressive neurodegenerative disease that affects motor skills. In addition to motor symptoms Jeremy has noticed changes in his mood. It is likely that Jeremy's __ is producing less __ than it needs to. A substantia nigra; acetylcholine B substantia nigra; dopamine C motor cortex; dopamine D motor cortex; acetylcholine

## Step 1<br />The problem is about the effects of Parkinson's disease on the brain. Parkinson's disease is a progressive neurodegenerative disorder that primarily affects motor skills. The question asks us to identify the part of the brain that is likely producing less of a certain neurotransmitter than it needs to, leading to the symptoms Jeremy is experiencing.<br /><br />## Step 2<br />The substantia nigra is a part of the brain that plays a crucial role in reward and movement. In Parkinson's disease, the neurons in the substantia nigra that produce dopamine, a neurotransmitter, start to die. This leads to a decrease in dopamine levels, which is responsible for the motor symptoms of Parkinson's disease.<br /><br />## Step 3<br />The motor cortex is involved in planning, controlling, and executing voluntary movements. However, it is not directly implicated in the production of dopamine or acetylcholine in the context of Parkinson's disease.<br /><br />## Step 4<br />Acetylcholine is another neurotransmitter that plays a role in the brain. In Parkinson's disease, the imbalance between dopamine and acetylcholine is not the primary issue. The disease is more about the deficiency of dopamine rather than an excess of acetylcholine.<br /><br />## Step 5<br />Given these points, the correct answer is the one that identifies the substantia nigra as the part of the brain producing less dopamine in the context of Parkinson's disease.