why damage to Area-4 of the brain causes Flaccid paralysis (reduced muscle tone) in the opposite side of the body
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.
Damage to Area-4 of the brain, also known as the primary motor cortex or M1, can lead to flaccid paralysis in the opposite side of the body, a condition known as hemiplegia. This occurs because Area-4 is responsible for initiating voluntary muscle movements.
Here is a step-by-step explanation of the process:
1. The brain sends signals to muscles through a network of neurons known as the corticospinal tract.
2. The corticospinal tract originates in the primary motor cortex (Area-4) of the brain, specifically its precentral gyrus region.
3. The neurons in this region of the primary motor cortex send signals through the corticospinal tract, which descends down the brainstem and spinal cord.
4. The corticospinal tract crosses over to the opposite side of the body at the level of the brainstem, specifically at the medulla.
5. After crossing over, the corticospinal tract continues down the opposite side of the spinal cord.
6. The corticospinal tract fibers terminate at various levels of the spinal cord, where they connect with lower motor neurons in the ventral horn.
7. Lower motor neurons, located in the ventral horn of the spinal cord, carry signals from the brain to the muscles.
8. These lower motor neurons then innervate the muscles, enabling voluntary movement.
9. When there is damage to Area-4, such as due to stroke or trauma, the ability of the primary motor cortex to initiate voluntary muscle movements is impaired.
10. As a result, the signals from the brain through the corticospinal tract cannot reach the corresponding muscles on the opposite side of the body effectively.
11. This leads to a reduction in muscle tone, resulting in flaccid paralysis on the opposite side of the body.
It is worth noting that flaccid paralysis caused by damage to the primary motor cortex is different from spastic paralysis, which is caused by damage to the upper motor neurons in the corticospinal tract, usually at the level of the spinal cord.
Damage to Area-4 of the brain, also known as the primary motor cortex or the precentral gyrus, can result in flaccid paralysis in the opposite side of the body. This phenomenon is due to the organization of the motor pathways in our brain.
To understand why this happens, it's important to know a bit about the brain's anatomy. The primary motor cortex is located in the frontal lobe, in the area controlling voluntary movements. It is responsible for sending signals to the muscles of the body, initiating and directing movement. However, the motor pathways are structured in a way that allows for the opposite side of the body to be controlled by each hemisphere of the brain.
When we want to move a specific body part, the primary motor cortex sends signals through a bundle of nerve fibers called the corticospinal tract. These nerves decussate, or cross over, at the level of the brainstem. This means that the left hemisphere controls the right side of the body, and the right hemisphere controls the left side of the body.
Now, in the case of damage to Area-4 in one hemisphere of the brain, such as from a stroke, the signals from the primary motor cortex cannot reach the muscles on the opposite side of the body. This disruption in the corticospinal tract disables the ability to initiate voluntary movements and results in flaccid paralysis.
Flaccid paralysis is characterized by reduced muscle tone, muscle weakness, and loss of reflexes. It means that the affected muscles become flabby and unresponsive, rather than being in a state of normal contraction. This happens because the neural information necessary for muscle activation is disrupted due to the damaged cortical area.
To diagnose the specific area of damage, medical imaging techniques such as MRI or CT scans are used. Additionally, a thorough medical examination and evaluation of symptoms can help pinpoint the region affected.
It's important to note that other brain regions and pathways, such as the corticobulbar tract, which controls the muscles of the face and head, may also be involved in producing paralysis in specific regions of the body. Each area of the brain has its own function, and damage to any of these regions can lead to specific impairments.