Which part of the body is primarily controlled by the primary motor cortex of the right cerebral hemisphere?

• A. Only the lower limbs
• B. The right side of the body
• C. Both sides of the body equally
• D. The left side of the body

Answer: (D)

Verified step by step guidance

1. Understand the role of the primary motor cortex: The primary motor cortex is located in the precentral gyrus of the frontal lobe and is responsible for voluntary motor control. Each hemisphere of the brain controls the opposite side of the body due to the crossing of motor pathways.
2. Learn about the concept of contralateral control: The motor signals from the primary motor cortex cross over to the opposite side of the body at the level of the medulla oblongata in the brainstem. This phenomenon is known as decussation.
3. Identify the hemisphere in question: The problem specifies the primary motor cortex of the right cerebral hemisphere. Based on contralateral control, this hemisphere will primarily control the left side of the body.
4. Eliminate incorrect options: The lower limbs are not exclusively controlled by the primary motor cortex of the right hemisphere, and the right hemisphere does not control the right side of the body or both sides equally. These options can be ruled out based on the anatomy of motor control.
5. Conclude the correct answer: Based on the contralateral control of motor function, the primary motor cortex of the right cerebral hemisphere primarily controls the left side of the body.