How does spinal cord work

What Does the Spinal Cord Do? Author: Spinalcord. Because the spinal cord both sends and receives important information about the body and the surrounding environment, it is indispensable to the regulation of a range of bodily functions, including: Regulating heart rate. Assessing temperature, and helping your body appropriately respond to cool or warm itself when temperatures are inappropriate. Maintaining homeostasis—relatively consistent internal body conditions.

By sending signals about the body's state, the spinal cord allows the brain to react with signals that initiate a cascade of changes. For example, if the spinal cord sends signals to the brain indicating that you are cold, you may begin shivering or seek out a blanket. Regulating breathing. Coordinating Reflexes The spinal cord also coordinates most reflexive responses, allowing you to quickly respond to changing stimuli without consciously becoming aware of the change.

Parts of the Spinal Cord The spinal cord acts as a single unit, receiving signals and sending them up the brain, and coordinating signals to send outward to the rest of the body. Nerve tracts exit the spinal cord and travel across the body from the spine at following regions: Cervical spinal cord : Consisting of eight bones, descending from C1-C8, this region plays a role in critical functions such as breathing and movement of the upper torso.

Injuries to the cervical spine almost inevitably result in quadriplegia, paralysis of all four limbs. Injuries high in the cervical spinal cord can be fatal. Thoracic spinal cord : Consisting of 12 bones, descending from T1-T12, the thoracic spinal cord helps coordinate movement in the lower body.

Injuries to this region often result in quadriplegia, paralysis below the waist. Lumbar spinal cord : Consisting of five bones, descending from L1-L5, the lumbar spinal cord coordinates sensations in lower regions of the body. The effects of damage to this area vary greatly, but lumbar spinal injuries sometimes impede bladder and sexual function. Sacral spinal cord : Also consisting of five bones, descending from S1-S5, sacral spine injuries can undermine sensation in lower regions of the body, as well as chronic pain.

Coccyx : Known sometimes as the coccygeal spine or tail bone, this region consists of between three and five distinct bones that may be fused together. It has nerve cells called neurons that are divided into white matter, which has a fatty white coating called myelin, and gray matter. The spinal cord is protected by the bony spine. When the spinal cord is injured, the injury happens in two stages: the first of these is the actual injury where the cord is bruised or torn and the second is known as the secondary injury.

The secondary injury includes a few different reactions that happen in the body because of the bruising and tearing. Spinal cord injuries can cause a person to lose feeling or use of their arms and legs, so scientists are working to find different ways of stopping or reducing the secondary injury to help people with spinal cord injuries recover better.

The spinal cord is very important. It is the main pathway for information to travel between the brain and all the other parts of the body. Through this communication, we are able to feel sensations, like pain, and control the movement of our arms and legs.

These messages traveling to and from the brain are sent by specialized nerve cells, called neurons Figure 1. The neurons may also have a white fatty coating, known as the myelin sheath my-uh-lin sheath , which helps the messages—like the pain from someone standing on your toe—to travel to the brain more quickly.

Most of the neurons with myelin are found in an area of the spinal cord known as white matter and they surround the cells without myelin, which are located in the area called the gray matter. The gray matter also contains most of the spinal cord blood vessels, which provide nutrients and oxygen to the neurons.

Also important is the bony spine or backbone, which protects all the cells and structures of the spinal cord. This backbone, made up of smaller bones called vertebrae ver-tuh-bray , keeps the spinal cord safe from any bashes and bangs.

The vertebrae are organized into levels cervical, thoracic, lumbar, and sacral , based on where they are in comparison to the head and the tail bone Figure 2B. Each of these spinal cord levels controls the movement and feeling of a particular body area.

The cervical level, closest to the head, controls the upper body, while the thoracic and lumbar segments are responsible for the lower body.

As a result of these functional differences, spinal cord segments are different sizes and have different amounts of gray and white matter Figure 2C. Like any other part of your body, the spinal cord can be injured. Some people damage their spinal cords when they dive into a swimming pool that is too shallow for diving, or even in a traffic accident.

When the spinal cord is damaged, the messages from the brain cannot travel to the rest of the body. Therefore, after a spinal cord injury, the brain may no longer be able to send messages to the legs and the affected person may lose his ability to walk. A higher injury, where the spinal cord is damaged closer to the neck in the cervical level , may cause even more severe problems and some people are left unable to move their arms.

Each neuron is made up of a cell body, which houses the nucleus. Axons and dendrites form extensions from the cell body. Astrocytes , a kind of glial cell, are the primary support cells of the brain and spinal cord.

They make and secrete proteins called neurotrophic factors. 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.