Textbook Question
The two cerebral hemispheres are functionally different, even though anatomically they appear the same.
(a) True
(b) False
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12. The Central Nervous System
The Cerebrum
3:03 minutesProblem 18
Textbook Question
What effect does injury to the primary motor cortex have on peripheral muscles?
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Understand the role of the primary motor cortex: The primary motor cortex, located in the precentral gyrus of the frontal lobe, is responsible for initiating voluntary motor movements by sending signals to peripheral muscles via motor neurons.
Identify the pathway of motor signals: Signals from the primary motor cortex travel through upper motor neurons, which synapse with lower motor neurons in the spinal cord or brainstem. Lower motor neurons then directly innervate peripheral muscles to produce movement.
Consider the effects of injury: Damage to the primary motor cortex disrupts the ability to send signals through upper motor neurons, leading to impaired voluntary control of muscles on the opposite side of the body (contralateral control).
Differentiate between types of motor impairments: Injury to the primary motor cortex can result in conditions such as paralysis (loss of movement) or paresis (weakness) in the affected muscles. Reflexes may still occur because lower motor neurons can function independently of the cortex.
Explore potential secondary effects: Over time, lack of use of the affected muscles can lead to muscle atrophy (wasting) and changes in muscle tone, such as spasticity or flaccidity, depending on the extent and nature of the injury.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Primary Motor Cortex Function
The primary motor cortex, located in the frontal lobe, is responsible for the voluntary control of skeletal muscles. It sends signals to the peripheral muscles through the spinal cord, facilitating movement. Damage to this area can disrupt the brain's ability to initiate and coordinate muscle contractions, leading to weakness or paralysis in affected regions.
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Primary Motor Cortex & Primary Somatosensory Cortex
Motor Pathways
Motor pathways are neural routes that transmit signals from the brain to the muscles. The corticospinal tract is the primary pathway for voluntary motor control, connecting the primary motor cortex to spinal motor neurons. Injury to the primary motor cortex can impair these pathways, resulting in diminished motor function in the peripheral muscles innervated by the affected neurons.
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Neuroplasticity
Neuroplasticity refers to the brain's ability to reorganize itself by forming new neural connections throughout life. After an injury to the primary motor cortex, other areas of the brain may adapt to compensate for lost functions, potentially restoring some degree of motor control. Understanding neuroplasticity is crucial for rehabilitation strategies aimed at recovering muscle function following such injuries.
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