Scientists have proven a 60-year-old theory about how nerve signals are transmitted through the body at varying speeds as electrical impulses. Researchers tested how signals are transmitted through nerve fibers, enabling movement and sensation. They found that the longer the insulating myelin layer between gaps in the fibers, called nodes, the faster the signals are conducted. This validates a theory first proposed by Nobel laureate Sir Andrew Huxley. The study also confirmed that the protein periaxin regulates the length of myelin layers and provides insight into nerve development and regeneration.

1. Anatomy and Physiology
Article 12 / 20 /12
How Nerve Signals Are Sent also shed light on how nerves develop
Around the Body at Varying Speeds before and after birth.
as Electrical Impulses
Professor Peter Brophy, Director of the
University of Edinburgh's Centre for
Oct. 11, 2012 — Scientists have proved a
Neuroregeneration, said: "The study gives
60-year-old theory about how nerve signals
us greater insight into how the central and
are sent around the body at varying speeds
peripheral nervous systems work and what
as electrical impulses.
happens after nerves become injured. We
know that peripheral nerves have the
Researchers tested how these signals are
capacity to repair, but shorter lengths of
transmitted through nerve fibres, which
insulation around the nerve fibres after
enables us to move and recognise sensations
repair affect the speed with which impulses
such as touch and smell.
are sent around the body."
The findings from the University of
The researchers found that when the myelin
Edinburgh have validated an idea first
reached a certain length, the speed with
proposed by Nobel laureate Sir Andrew
which nerves impulses were conducted
Huxley.
reached a peak.
It has been known for many years that an
The study, carried out in mice, also
insulating layer -- known as myelin -- which
confirmed that a protein -- periaxin -- plays
surrounds nerve fibres is crucial in
a key role in regulating the length of myelin
determining how quickly these signals are
layers around nerve fibres.
sent.
Review Questions – Cornell Format
This insulating myelin is interrupted at
regular intervals along the nerve by gaps 1. According to the article, what have
called nodes. scientists proved?
Scientists, whose work was funded by the 2. What do signals transmitted through
Wellcome Trust, have now proved that the nerve fibers allow us to do?
longer the distance between nodes, the
quicker the nerve fibres send signals down 3. What is the name of the insulating layer
the nerves. that allows nerve signals to be sent
quickly throughout the body?
The theory that the distance between these
gaps might affect the speed of electrical 4. What are the interruptions of the
signals was first proposed by Sir Andrew insulating layer at regular intervals
Huxley, who won the Nobel Prize in 1963
called?
for his work on electrical signalling in the
nervous system, and who died earlier this 5. Who was the first person to propose
year.
the theory on the speed of nerve
impulses?
The study, published in the journal Current
Biology, will help provide insight into what
happens in people with nerve damage. It will

2. Anatomy and Physiology
Article 12 / 20 /12
6. What happens to the insulation of
peripheral nerve fibers after injury?
7. What did researchers discover about
the protein, periaxin?