Science & Technology in Action

12th Edition

What is multiple sclerosis?


In multiple sclerosis the myelin sheath surrounding neurons is attacked by the body’s defence systems resulting in the slowing down of the signal or even its blockage. Even if a signal is just slowed down it will cause responses to go out of synch and become ineffective.
Download Lesson Kit

Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

What is multiple sclerosis (MS)?
MS is a chronic autoimmune disease of the CNS (brain and spinal cord) first described by the French neurologist Jean-Martin Charcot in 1868. It is chronic because it goes on over many years, albeit most frequently in bouts, and autoimmune because the body’s immune system attacks part of itself (the myelin sheath surrounding axons and dendrites) mistaking it for a pathogen. It is also called a demyelinating disease.

It usually makes its fi rst appearance between the ages of 20 and 40, affecting around 9000 people in Ireland, with women affected twice as often as men. The annual cost to the economy is estimated at around €450 million.

No two people’s symptoms are the same; they vary from fatigue, numbness, problems urinating or with vision, to the most obvious symptom − difficulties with mobility. Blurred or double vision is one of the commonest first symptoms and about 50% of those affected will need help with walking within 15 years of the onset of the disease.

The precise cause of the disease is unknown. However, there is a general consensus that there is a genetic component involving a combination of several genes and some researchers suspect vitamin D levels may also be involved as the occurrence of the disease increases as one moves further away from the bright sun of the equator.

The Nervous system
The nervous system is a co-ordination and communication system that uses electrical impulses to convey information very rapidly. It consists of two main sections: the peripheral nervous system and the central nervous system. The peripheral system collects information and conveys it to the central system, which coordinates it and decides on an appropriate response. This is then conveyed to the effectors (muscles or glands) using the peripheral system.

True or False?

  1. MS was first described in the twentieth century. false
  2. MS is a short term autoimmune disease. false
  3. The central nervous system consists of the brain and spinal cord. true
  4. The myelin sheath insulates and protects neurons. true
  5. Interneurons connect sensory receptors to the CNS. false
  6. Intravenous injections are given between veins. false
  7. There are more than three different types of MS classified by the part of the body they affect. false
  8. A period when the symptoms of MS go away is called remission. true
  9. Half of those suffering from MS will need help walking within 15 years of the onset of the disease. true
  10. The myelin sheath can be repaired resulting in a lessening of symptoms. true
  11. Diagnosis of MS is a simple process. false

Glossary of terms

a cancer that does not spread to other parts of the body
a microorganism that is capable of causing disease in a specific host
a multipolar neuron that connects sensory neurons to motor neurons
an extension of the nerve cell body that carries impulses away from the nerve cell
autoimmune diseases are those in which the body's defence system attacks the body's own cells
functional unit of the body's nervous system; neurons make up the nervous system and allow different parts of the body to communicate with each other
persistent or long lasting
central nervous system
portion of the vertebrate nervous system consisting of the brain and spinal cord
cell body
the part of a nerve cell that contains the nucleus
within or injected into a vein
clinically isolated syndrome (CIS)
a term used by doctors to describe the first attack of MS
demyelinating disease
another name for MS where the myelin is removed from the neuron
part of the nerve cell that conducts the impulse towards the cell body
muscles and glands that are controlled by the nervous system
worn away
into the muscle
MRI scan
a picture produced using magnetic resonance induction similar to an X-ray but much more detailed
myelin sheath
fatty covering found on some neurons that insulates the conductive tissue and speeds up the impulse
peripheral nervous system
the nervous system outside the brain and spinal cord consisting of sensory receptors, sensory neurons and motor neurons
a period of time when the symptoms return
a period of time when the symptoms lessen or disappear
the process of renewing myelin that has been reduced
a distinctive scar produced by the attack of the immune system on the myelin sheath
sensory receptor
structures that collect information about changes in the environment
below the skin