A patient has suffered a cerebral hemorrhage that has caused dysfunction of the precentral gyrus of his right cerebral cortex. As a result, a. he cannot voluntarily move his left arm or leg, b. he feels no sensation on the left side of his body, c. he feels no sensation on his right side.

Verified step by step guidance

1. Identify the location of the precentral gyrus in the brain, which is part of the frontal lobe and is responsible for voluntary motor control.
2. Understand that the precentral gyrus is also known as the primary motor cortex, which controls voluntary movements of the opposite side of the body.
3. Recognize that a cerebral hemorrhage affecting the right precentral gyrus would impact motor functions on the left side of the body due to the crossing of motor pathways in the brain.
4. Consider the options given: (a) inability to move the left arm or leg voluntarily, (b) no sensation on the left side, and (c) no sensation on the right side.
5. Determine that the correct answer is related to motor dysfunction on the left side, as the precentral gyrus is primarily involved in motor control, not sensory perception.

Key Concepts

Precentral Gyrus Function

The precentral gyrus, located in the frontal lobe of the brain, is primarily responsible for voluntary motor control. It contains the primary motor cortex, which sends signals to muscles to initiate movement. Damage to this area can lead to motor deficits, such as the inability to move limbs on the opposite side of the body, as seen in this patient.

Contralateral Control

The principle of contralateral control refers to the brain's organization where one hemisphere controls the opposite side of the body. For instance, damage to the right precentral gyrus affects the left side of the body. This concept is crucial for understanding the patient's inability to move his left arm and leg following the hemorrhage.

Sensory Pathways

Sensory pathways transmit information from the body to the brain, allowing for the perception of sensations such as touch, pain, and temperature. The right side of the brain processes sensory information from the left side of the body. Dysfunction in the precentral gyrus can disrupt these pathways, leading to a loss of sensation on the affected side, as indicated in the patient's symptoms.