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Grey and white matter In terms of tissue, the CNS is divided into grey matter and white matter. They also break down and remove proteins or chemicals that might be harmful to neurons for example, glutamate, a neurotransmitter that in excess causes cells to become overexcited and die by a process called excitotoxicity.
Astrocytes aren't always beneficial: after injury, they divide to make new cells that surround the injury site, forming a glial scar that is a barrier to regenerating axons. Microglia are immune cells for the brain. After injury, they migrate to the site of injury to help clear away dead and dying cells. They can also produce small molecules called cytokines that trigger cells of the immune system to respond to the injury site.
This clean-up process is likely to play an important role in recovery of function following a spinal injury. Messages are passed from neuron to neuron through synapses, small gaps between the cells, with the help of chemicals called neurotransmitters. To transmit an action potential message across a synapse, neurotransmitter molecules are released from one neuron the "pre-synaptic" neuron across the gap to the next neuron the "post-synaptic" neuron. The process continues until the message reaches its destination.
There are millions and millions of connections between neurons within the spinal cord alone. These connections are made during development, using positive neurotrophic factors and negative inhibitory proteins signals to fine-tune them. Amazingly, a single axon can form synapses with as many as 1, other neurons.
There is a logical and physical topographical organization to the anatomy of the central nervous system, which is an elaborate web of closely connected neural pathways. This ordered relationship means that different segmental levels of the cord control different things, and injury to a particular part of the cord will have an impact on neighboring parts of the body.
Paralysis occurs when communication between the brain and spinal cord fails. This can result from injury to neurons in the brain a stroke , or in the spinal cord. Trauma to the spinal cord affects only the areas below the level of injury.
However, poliomyelitis a viral infection or Lou Gehrig's disease amyotrophic lateral sclerosis, or ALS can affect neurons in the entire spinal cord. Specialized neurons carry messages from the skin, muscles, joints, and internal organs to the spinal cord about pain, temperature, touch, vibration, and proprioception. These messages are then relayed to the brain along one of two pathways: the spinothalmic tract and the lemniscal pathway.
These pathways are in different locations in the spinal cord, so an injury might not affect them in the same way or to the same degree. Each segment of the spinal cord receives sensory input from a particular region of the body.
Scientists have mapped these areas and determined the "receptive" fields for each level of the spinal cord. Neighboring fields overlap each other, so the lines on the diagram are approximate. Over one million axons travel through the spinal cord, including the longest axons in the central nervous system.
Neurons in the motor cortex, the region of the brain that controls voluntary movement, send their axons through the corticospinal tract to connect with motor neurons in the spinal cord. The spinal motor neurons project out of the cord to the correct muscles via the ventral root.
These connections control conscious movements, such as writing and running. Information also flows in the opposite direction resulting in involuntary movement. Sensory neurons provide feedback to the brain via the dorsal root. Some of this sensory information is conveyed directly to lower motor neurons before it reaches the brain, resulting in involuntary, or reflex movements. The remaining sensory information travels back to the cortex.
The spinal cord is divided into five sections: the cervical, thoracic, lumbar, sacral, and coccygeal regions. No two injuries are alike. This diagram illustrates the connections between the major skeletal muscle groups and each level of the spinal cord. A similar organization exists for the spinal control of the internal organs.
In addition to the control of voluntary movement, the central nervous system contains the sympathetic and parasympathetic pathways that control the "fight or flight" response to danger and regulation of bodily functions.
These include hormone release, movement of food through the stomach and intestines, and the sensations from and muscular control to all internal organs. This diagram illustrates these pathways and the level of the spinal cord projecting to each organ. Although spinal cord injury causes complex damage, a surprising amount of the basic circuitry to control movement and process information can remain intact. This is because the spinal cord is arranged in layers of circuitry.
Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. The central nervous system CNS is comprised of the brain and spinal cord. The CNS receives sensory information from the nervous system and controls the body's responses.
The CNS is differentiated from the peripheral nervous system , which involves all of the nerves outside of the brain and spinal cord that carry messages to the CNS. The central nervous system plays a primary role in receiving information from various areas of the body and then coordinating this activity to produce the body's responses. The CNS has three main components: the brain, the spinal cord, and the neurons or nerve cells. The brain controls many of the body's functions including sensation, thought, movement, awareness, and memory.
The surface of the brain is known as the cerebral cortex. The surface of the cortex appears bumpy thanks to the grooves and folds of the tissue. Each groove is known as a sulcus, while each bump is known as a gyrus. The largest part of the brain is known as the cerebrum and is responsible for things such as memory, speech, voluntary behaviors, and thought.
The cerebrum is divided into two hemispheres, a right hemisphere, and a left hemisphere. The brain's right hemisphere controls movements on the body's left side, while the left hemisphere controls movements on the body's right side. While some functions do tend to be lateralized, researchers have found that there are not "left brained" or "right brained" thinkers , as the old myth implies.
Each hemisphere of the brain is then divided into four interconnected lobes :. The spinal cord connects to the brain via the brain stem and then runs down through the spinal canal, located inside the vertebra. The spinal cord carries information from various parts of the body to and from the brain. In the case of some reflex movements, responses are controlled by spinal pathways without involvement from the brain.
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