HOW THE BRAIN CONTROL MOVEMENT

HOW THE BRAIN CONTROL MOVEMENT

The brain controls movement through a complex, hierarchical system involving multiple regions that The brain controls voluntary movement through a precisely organized, hierarchical system that begins with intent and ends with the contraction of specific muscles. This is primarily executed via the motor pathways (descending tracts) involving several key brain regions.

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🧠 Key Brain Regions for Movement

Movement is not controlled by a single area, but by a network of structures that coordinate planning, initiation, execution, and correction.

1. Cerebral Cortex (The Planner and Initiator):

   • Premotor Cortex and Supplementary Motor Area: These areas in the frontal lobe are involved in the planning and sequencing of complex movements (e.g., deciding the steps to pick up a cup).

   • Primary Motor Cortex (M1): Located in the frontal lobe's precentral gyrus, this is where the final, specific commands to initiate a voluntary movement are generated. It operates a motor homunculus, a map where different parts of the cortex control specific body parts (the hands and face take up the most space).

2. Cerebellum (The Coordinator and Corrector):

   • The cerebellum is essential for coordination, balance, and fine-tuning movement. It constantly compares the intended movement from the cortex with the actual movement reported by the body's sensory feedback, correcting any errors in real-time.

3. Basal Ganglia (The Regulator):

   • A group of deep structures that act as a gate, regulating the initiation and suppression of movements. They select the appropriate motor program and inhibit unwanted movements, which is why damage here (as in Parkinson's disease) leads to tremors and difficulty initiating movement.

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⚡ The Motor Pathway (The Command Line)

The signal to move travels from the cortex down the primary descending pathway, the Corticospinal Tract, using two main types of neurons:

1. Upper Motor Neuron (UMN)

• Origin: The cell body of the UMN is located in the Primary Motor Cortex.

• Decussation (The Crossover): The axon of the UMN travels down through the brainstem. In the medulla oblongata, the majority of the fibers cross over (decussate) to the opposite side of the central nervous system.

• Descent: The pathway continues down the spinal cord on the side opposite to its origin (the contralateral side). This is why the left side of your brain controls the right side of your body, and vice-versa.

2. Lower Motor Neuron (LMN)

• Synapse: The UMN axon synapses with the LMN cell body in the ventral horn of the spinal cord (or in the brainstem for face/neck movements).

• Action: The LMN axon then leaves the spinal cord and travels through peripheral nerves to the skeletal muscle, where it releases neurotransmitters (acetylcholine) at the neuromuscular junction, causing the muscle to contract.

Diagram of Brain

The area of the brain that controls movement is in a very narrow strip that goes from near the top of the head right down along where your ear is located. 

It's called the motor strip. If I injure that area, I'll have problems controlling half of my body. If I have a stroke in the left hemisphere of my brain, the right side of the body will stop working. 

If I have an injury to my right hemisphere in this area, the left side of my body stops working (remember, we have two brains). This is why one half of the face may droop when a person has had a stroke. Diagram of Brain

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