Spinal cord

Spinal Cord Sectional Anatomy

• The spinal cord extends from the foramen magnum at the base of the skull to the level of the first lumbar vertebra.
• The cord is continuous with the medulla oblongata.
• Like the brain, the spinal cord is surrounded by bone, meninges, and cerebrospinal fluid.

Divisions

Spinal Cord Segments and body representation

• The spinal cord is divided into 31 segments with each segment giving rise to a pair of spinal nerves.
• At the distal end of the cord, many spinal nerves extend beyond the conus medullaris to form a collection that resembles a horse's tail.
• This is the cauda equina.
• In cross section, the spinal cord appears oval in shape.

Functions

The spinal cord has two main functions:

• Serving as a conduction pathway for impulses going to and from the brain.

Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts.

• Serving as a reflex center. The reflex arc is the functional unit of the nervous system.
• Reflexes are responses to stimuli that do not require conscious thought and consequently, they occur more quickly than reactions that require thought processes.
• For example, with the withdrawal reflex, the reflex action withdraws the affected part before you are aware of the pain.
• Many reflexes are mediated in the spinal cord without going to the higher brain centers.

a schematic diagram showing anatomical signification of incomplete cord injuries

Spinal cord injuries

• A spinal cord injury usually begins with a sudden, traumatic blow to the spine that fractures or dislocates vertebrae.
• The damage begins at the moment of injury when displaced bone fragments, disc material, or ligaments bruise or tear into spinal cord tissue.
• Most injuries to the spinal cord don't completely sever it.
• Instead, an injury is more likely to cause fractures and compression of the vertebrae, which then crush and destroy axons -- extensions of nerve cells that carry signals up and down the spinal cord between the brain and the rest of the body.
• An injury to the spinal cord can damage a few, many, or almost all of these axons.
• Some injuries will allow almost complete recovery. Others will result in complete paralysis

Types of spinal cord injuries

• Spinal cord injuries are classified as either complete or incomplete. 
• An incomplete injury means that the ability of the spinal cord to convey messages to or from the brain is not completely lost. People with incomplete injuries retain some motor or sensory function below the injury. 
• A complete injury is indicated by a total lack of sensory and motor function below the level of injury. 
• People who survive a spinal cord injury will most likely have medical complications such as chronic pain and bladder and bowel dysfunction, along with an increased susceptibility to respiratory and heart problems.
• Successful recovery depends upon how well these chronic conditions are handled day to day. Surgery to relieve compression of the spinal tissue by surrounding bones broken or dislocated by the injury is often necessary, through timing of such surgery may vary widely.  

Treatment

• Improved emergency care for people with spinal cord injuries and aggressive treatment and rehabilitation can minimize damage to the nervous system and even restore limited abilities. 
• Respiratory complications are often an indication of the severity of spinal cord injury
• About one-third of those with injury to the neck area will need help with breathing and require respiratory support.
• The steroid drug methylprednisolone appears to reduce the damage to nerve cells if it is given within the first 8 hours after injury.  Rehabilitation programs combine physical therapies with skill-building activities and counseling to provide social and emotional support. Electrical simulation of nerves by neural prosthetic devices may restore specific functions, including bladder, breathing, cough, and arm or leg movements

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External links

• Comprehensive information from the National Institute of health.
  

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