Textbook Question
The primary motor cortex, Broca's area, and the premotor cortex are located in which lobe?
a. Frontal
b. Parietal
c. Temporal
d. Occipital
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12. The Central Nervous System
The Cerebrum
2:27 minutesProblem 12
Textbook Question
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 guidance1
Understand the anatomy of the precentral gyrus: The precentral gyrus is located in the frontal lobe of the brain and is the primary motor cortex responsible for voluntary motor control. It controls movements on the opposite side of the body due to the crossing of motor pathways in the brainstem.
Analyze the effects of damage to the precentral gyrus: Dysfunction in the precentral gyrus would primarily affect voluntary motor control, not sensory perception. Sensory functions are controlled by the postcentral gyrus (primary somatosensory cortex).
Determine the side of the body affected: Since the precentral gyrus of the right cerebral cortex is damaged, the left side of the body will be affected due to the contralateral control of motor functions.
Evaluate the symptoms described in the options: Option (a) aligns with the role of the precentral gyrus, as it explains the inability to voluntarily move the left arm or leg. Option (b) and (c) are incorrect because sensory loss is not directly related to the precentral gyrus but rather to the postcentral gyrus.
Conclude the correct answer based on the analysis: The correct answer is (a), as the dysfunction of the precentral gyrus on the right side of the brain results in the inability to voluntarily move the left arm or leg.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cerebral Hemorrhage
A cerebral hemorrhage refers to bleeding within the brain, which can disrupt normal brain function. This condition can lead to increased intracranial pressure and damage to brain tissue, particularly affecting areas responsible for motor control and sensation. Understanding this concept is crucial as it sets the stage for the neurological deficits observed in the patient.
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Cerebral White Matter
Precentral Gyrus
The precentral gyrus, located in the frontal lobe of the brain, is the primary motor cortex responsible for voluntary movement. Each hemisphere of the brain controls the opposite side of the body, meaning damage to the right precentral gyrus affects the left side. This concept is essential for understanding why the patient cannot move his left arm or leg.
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Contralateral Sensation and Motor Control
Contralateral sensation and motor control refer to the phenomenon where one side of the brain controls and senses the opposite side of the body. In this case, damage to the right cerebral cortex results in loss of movement and sensation on the left side. This principle is fundamental in diagnosing and understanding the effects of the patient's cerebral hemorrhage.
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