The brain controls movement through a complex, hierarchical system involving multiple regions thatThe 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.
🧠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.
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).
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.
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.
⚡ 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).
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
Brain tumors are broadly classified based on where they originate (primary or metastatic) and the type of cell they arise from.1The World Health Organization (WHO) also assigns a grade from I to IV based on how aggressive the cells are.2
Here is an overview of the types of brain cancer and tumors:
1. Primary Brain Tumors3
These tumors originate within the brain or spinal cord tissue.4They are often named after the cells they resemble.5
A. Gliomas (The Most Common Type)
Gliomas arise from glial cells, the supportive cells of the brain.6They are categorized by the specific type of glial cell they develop from:7
A rare, aggressive cancer of the immune cells that starts in the brain or spinal cord.
2. Metastatic (Secondary) Brain Tumors8
These are cancers that start in another part of the body (e.g., lung, breast, skin/melanoma, colon) and spread to the brain.9
Key Fact: Metastatic tumors are far more common than primary brain tumors.10
The tumor is named and treated according to the tissue of origin (e.g., metastatic lung cancer to the brain).11
The WHO Brain Tumor Grading System
The World Health Organization (WHO) classifies brain tumors into four grades based on how the cells look under a microscope (histology) and their likely behavior:12
WHO Grade
Classification
Characteristics
Grade I
Benign / Low-Grade
Slowest growing; least malignant; often curable with surgery alone.
Grade II
Low-Grade
Grow slowly but may spread into nearby tissue; can potentially recur as a higher grade.
Grade III
Malignant / High-Grade
Faster growing; cells are abnormal (anaplastic); likely to recur.
Grade IV
Malignant / High-Grade
Fastest growing; most aggressive and invasive (e.g., Glioblastoma).
There are over 100 types of cancer that can affect the central nervous system (CNS).16 As mentioned previously, cancers that arise in other locations (breast, lung, etc.) and spread (metastasize) to the brain are not considered brain cancer. They are still treated as the cancers of the original site. Here, we will only discuss primary brain cancers (those that originate in the brain).
Gliomas
Malignant gliomas are the most common and deadly brain cancers. They originate in the glial cells of the central nervous system (CNS). Gliomas can be divided into 3 main types:
astrocytomas,
oligodendrogliomas, and
ependymomas.
The median survival of patients with glioma has improved over the past few years but is still only 15 months, with few patients living more than two years.Research indicates that this type of brain cancer may resist treatment because it contains stem cells that are responsible for driving the formation of blood vessels (angiogenesis), spread of the tumor (metastasis), and resistance to treatments.
Astrocytomas:
Astrocytomas are tumors that develop in astrocytes and are found in the cerebrum and the cerebellum. Astrocytomas make up approximately 50% of all primary brain tumors. Glioblastoma multiforme, an astryocytoma subtype, is the most aggressive form of brain cancer and is associated with poor prognosis.
Oligodendrogliomas:
Oligodendrogliomas are tumors that develop in oligodendrocytes, and more often in the oligodendrocytes that are found in the cerebral hemispheres. Oligodendrocytes are glial cells that produce myelin, a component of the brain that increases impulse speed. Oligodendrogliomas make up approximately 4% of primary brain tumors. Approximately 55% of all cases of oligodendrogliomas appear in people between the ages of 40 and 64.
Ependymomas:
Ependymomas are tumors that develop in the ependymal cells. Ependymal cells are the cells in the brain and where ceribrospinal fluid (CSF) is created and stored. 24Ependymomas account for only 2% to 3% of all primary brain tumors but account for 8% to 10% of brain tumors in children. Ependymoma tumors are usually found in ventricle linings, the spinal cord, or the regions near the cerebellum.
Nongliomas are tumors that do not arise from glial cells. More prevalent examples of nongliomas include meningiomas and medulloblastomas. Less prevalent examples include medullpituitary adenomas, primary CNS lymphomas, and CNS germ cell tumors.
Meningiomas:
Meningiomas are tumors that develop in the meninges, membranes covering the brain and spinal cord. Meningioma tumors are frequently formed from arachnoid cells. These cells are responsible for the absorption of the cerebrospinal fluid (CSF). Meningioma tumors are responsible for 13% to 30% of all tumors arising within the cranium - the bony case surrounding the brain. Tumor arising within the cranium are also called intracranial tumors. Most meningiomas are benign. Malignant meningiomas are extremely rare, with an incidence rate of approximately two out of every million people, per year. The risk for developing meningiomas increases with age and is more prevalent in women.
Medulloblastomas:
Medulloblastomas are the most common brain malignancies in children. These cancers arise in the posterior fossa - a specific region of the space inside the skull (intracranial cavity) that contains the brainstem and the cerebellum. The fourth ventricle region is involved in the development of approximately 80% of childhood cases.
Getting information into and out of the brain relies on the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) working together via specialized neural pathways.
The flow of information is categorized into two main directions:
Input (Afferent/Sensory): Information coming into the CNS (brain and spinal cord).
Output (Efferent/Motor): Information going out of the CNS to the body's effectors (muscles and glands).
👂 Input: Sensory (Afferent) Pathways
Sensory information from the environment (e.g., sight, touch, pain) travels toward the brain via sensory neurons.
Peripheral Receptors: Specialized sensory receptors in the skin, eyes, ears, and internal organs detect stimuli (e.g., pressure, light, chemical signals).
Ascending Tracts: The impulse travels along the nerve fibers (axons) through peripheral nerves and then enters the spinal cord or brainstem.Once inside the spinal cord, it travels toward the brain in organized bundles called ascending tracts.
Body Below the Neck: Information ascends through the spinal cord.Major pathways, like the Spinothalamic Tract (for pain and temperature) and the Dorsal Column System (for fine touch and proprioception), carry the signal.
Processing Centers: The sensory signal is typically relayed in the thalamus (the brain's major relay center) before reaching its final destination in the cerebral cortex (e.g., the Somatosensory Cortex in the parietal lobe for touch, the Visual Cortex in the occipital lobe for sight).
💪 Output: Motor (Efferent) Pathways
Instructions for movement and gland function travel away from the brain to the body's muscles and glands via motor neurons.
Initiation: Voluntary movement instructions are typically initiated in the cerebral cortex, mainly the Primary Motor Cortex in the frontal lobe.
Descending Tracts: The instructions travel down from the cortex as electrical impulses along upper motor neurons through the brainstem and into the spinal cord in bundles called descending tracts. The most famous of these is the Corticospinal Tract, which controls voluntary, skilled movements of the limbs.
Relay in Spinal Cord: In the spinal cord, the upper motor neuron synapses (communicates) with a lower motor neuron.
Final Destination: The lower motor neuron's axon exits the spinal cord and travels through peripheral nerves to connect directly with the muscle fiber or gland, causing it to contract or secrete.
This constant, rapid flow of input (sensory) and output (motor) allows the brain to perceive the environment, process the information, and execute appropriate and timely responses.
How does information come into the brain?
A lot of information comes in through the spinal cord at the base of the brain. Think of a spinal cord as a thick phone cable with thousands of phone lines. If you cut that spinal cord, you won't be able to move or feel anything in your body. Information goes OUT from the brain to make body parts (arms and legs) do their job.
There is also a great deal of INCOMING information (hot, cold, pain, joint sensation, etc.). Vision and hearing do not go through the spinal cord but go directly into the brain. That’s why people can be completely paralyzed (unable to move their arms and legs) but still see and hear with no problems.
Information enters from the spinal cord and comes up the middle of the brain. It branches out like a tree and goes to the surface of the brain. The surface of the brain is gray due to the color of the cell bodies (that's why it's called the gray matter). The wires or axons have a coating on them that's colored white (called white matter).
GETTING INFORMATION IN AND OUT OF THE BRAIN VIDEO :
