Damage to Area-4 of the brain, also known as the primary motor cortex or the precentral gyrus, can lead to flaccid paralysis or reduced muscle tone on the opposite side of the body. This is because the primary motor cortex is responsible for initiating voluntary muscle movements.
The primary motor cortex is involved in the generation and execution of precise motor commands that control specific body parts. It sends signals through the descending motor pathways, particularly the corticospinal tract (also known as the pyramidal tract), to the spinal cord, which in turn activates the muscles on the opposite side of the body.
When Area-4 is damaged, the motor signals originating from that region are disrupted or weakened, causing a decrease in the ability to voluntarily contract and control the affected muscles. This can result in flaccid paralysis, characterized by limp, floppy muscles and a loss of muscle tone.
Furthermore, the corticospinal tract decussates (crosses over) in the medulla of the brainstem, meaning that motor signals from the left primary motor cortex control muscles on the right side of the body, and vice versa. Therefore, damage to Area-4 in one hemisphere of the brain will affect the opposite side of the body, leading to flaccid paralysis in the corresponding muscles on the other side.
why damage to Area-4 of the brain causes Flaccid paralysis (reduced muscle tone) in the opposite side of the body
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