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Brain pathways: an information superhighway
Understanding the neural network
The brain, our body's conductor, is a complex network of billions of interconnected neurons. These neurons communicate with each other via specialized pathways known as nerve tracts. These pathways are essential for transmitting sensory, motor and cognitive information throughout the body.
Main brain pathways
1. The pyramidal pathway
- Role: The pyramidal pathway is primarily responsible for the voluntary control of movement. It connects the primary motor cortex to the motor neurons in the spinal cord, enabling the initiation and control of precise skeletal muscle movements.
- Components: It comprises the corticospinal bundle and the corticobulbar bundle.
- How it works: Nerve signals from the motor cortex travel down this pathway to activate the muscles concerned.
2. Sensory pathways
- Role: These pathways transmit sensory information from the body to the brain.
- Types of sensitivity:
o Tactile sensitivity: Allows us to perceive touch, pressure and vibration.
o Thermal sensitivity: Allows us to perceive heat and cold.
o Deep sensitivity: Allows us to perceive the position of limbs in space (proprioception) and joint movements.
o Pain sensitivity: Allows us to perceive pain.
- Pathway: Sensory information is transmitted by peripheral nerves to the spinal cord, then back to the brain via various ascending pathways.
3. Specific sensory pathways
- Visual: transmits visual information from the retina to the occipital lobe.
- Auditory: Transmits auditory information from the inner ear to the temporal lobe.
- Olfactory pathway: transmits olfactory information from olfactory receptors to the olfactory bulb.
- Taste pathway: transmits taste information from the taste buds to the taste cortex.
4. Proprioception pathway
- Role: Proprioception is the sense that enables us to know our body's position in space.
- How it works: Proprioceptive receptors in muscles, tendons and joints constantly send information to the brain about the state of muscle contraction, joint angle and limb position.
- Importance: Proprioception is essential for movement coordination, balance and posture.
Nerve pathway disorders
Damage to or dysfunction of these pathways can lead to a variety of neurological disorders, such as :
- Hemiplegia: Paralysis of one side of the body.
- Paresthesia: Sensation of numbness or tingling.
- Ataxia: Loss of coordination of movements.
- Blindness: Loss of vision.
- Deafness: Loss of hearing.
In conclusion
Brain pathways are complex networks that ensure communication between the brain and the body. Understanding how they work is essential for grasping the mechanisms underlying many physiological and pathological processes.
Go further
Barrier Breakthrough
Your body contains hundreds of nerves but they can't all regenerate. After injury, peripheral nerves replace damaged sections but nerves in your central nervous system (CNS) can’t. Instead, brain cells called astrocytes cordon off damaged tissue (lesions) to help preserve healthy nerve tissue. These lesions form a barrier, preventing regeneration. Transplants of neural progenitor cells (NPCs), made from stem cells, may help. Researchers investigate by tagging NPCs and transplanting them, via a hydrogel, into uninjured or injured mouse CNS. RNA analysis revealed NPCs in uninjured mice matured into cells resembling healthy astrocytes, while NPCs in injured mice matured into cells resembling ‘reactive’ astrocytes, which arise after injury to partition off lesions. Fluorescence microscopy of injured CNS (pictured) revealed that adding NPCs (right) reduced lesion size (magenta) and helped bridge lesions via astrocytes (green) compared with injured CNS without NPCs (left) or only hydrogel (middle). The injury microenvironment, therefore, directs NPCs towards wound repair.
Written by Lux Fatimathas
Image from work by T. M. O’Shea and colleagues
Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
Published in Nature Communications, September 2022
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“Coloured model showing cutaneous root areas.” The diagnosis of nervous diseases. 1916. Internet Archive
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Nerve Study Shows How Cells Adapt to Help Repair Damage
Researchers focused on injury to cells in the peripheral nervous system (PNS) - the crucial network of nerves outside the brain and spinal cord.
The research is in Cell Reports. (full open access)
Bloody Networking
Social networks have nothing on the complexity of the networks of blood vessels and nerves that make your body tick. The blood vessels that supply your peripheral nerves – your intra-nervous vascular (INV) system – are essential for nerve function and repair. Researchers now investigate the mechanisms underlying INV development using mice. Fluorescence microscopy of the sciatic nerve in embryonic mice (pictured) revealed that blood vessels start invading this nerve around embryonic day 16. The team also found that a signal molecule involved in nerve and blood vessel development, netrin-1, promoted this process, as demonstrated by genetically interfering with netrin-1 function, which resulted in fewer blood vessels (magenta) supplying the developing nerve (green). This result was replicated when developing mice were injected with antibodies to block the protein that netrin-1 binds, the UNC5B receptor, which is found on blood vessels. Netrin-1 and UNC5B are therefore key players in INV development.
Written by Lux Fatimathas
Image from work by Sonia Taïb and colleagues
Center for Interdisciplinary Research in Biology (CIRB), College de France, CNRS, INSERM, Université PSL, Paris, France
Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
Published in eLife, January 2022
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Clean Break
Sometimes a clean break is the only way to end a once-beautiful relationship. Early in development, our central and peripheral nervous systems must separate from their shared starting point, the neural tube. The top of this collection of cells produces and releases the neural crest, a group of cells destined for, among other things, the peripheral nervous system. Eventually this release stops and the top region forms the roof plate crucial to the central nervous system. This fundamental separation could be key to neurodegenerative disorders, and the process has similarities to some cancer spreading mechanisms, so better understanding could help patients. A new study unveiled a key regulator of the separation, retinoic acid. Without it, the roof plate of bird embryos (pictured) continued to produce neural crest material (green) as well as the usual roof plate material (green) after the separation should have happened, blurring the distinction and damaging development.
Written by Anthony Lewis
Image from work by Dina Rekler and Chaya Kalcheim
Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Hebrew University of Jerusalem-Hadassah Medical School, Jerusalem, Israel
Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
Published in eLife, April 2022
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