The Spinal cord is an extension of the brain.
Messages from the different parts of the body travel
through it to the brain and back. The nerves in the
spinal cord carry these messages to and from your
The spinal cord enables us to do things
automatically. This automatic action is called reflex
action. For instance, when you touch a hot object
such as flat iron, you immediately withdraw your
hand. This action does not involve your brain
because you do not think at all whether you avoid
the hot object or not.
In a reflex action, the nerve impulses take a
special pathway called reflex arc.
In the case of your touching the flat iron,
the impulse moved from the skin (sensory
nerve) where it came into contact with flat iron
to your spinal cord.
Here, the impulses set off another impulse in a
motor nerve running from your spinal cord to
your arm muscles. The muscles contracted and
pulled your hand away from the flat iron. This
action took place less than 1/50 of a second. At
the same time, the original impulse traveled
up to your spinal cord to your brain, where you
feel it as pain.
A reflex is a rapid automatic response to the
environment that happened without action of the
brain. They can be a movement, as in motor
reflex. Blinking when suddenly comes too close to
the eyes is a motor reflex. Other reflex action can
be develop through memory. The brain
remembers how to respond to certain signals or
situations. This is called a conditioned reflex. A
conditioned reflex is based upon previous
experience. For example, hearing to an ice cream
van might make someone’s mouth water. This is
a conditioned reflex.
Another example is seeing and smelling
food you like most. Before you actually put the
food in your mouth, you see it and smell it. You
associate its appearance and odor with its
taste. As a result, when you see and smells
foods that you like, even though you do not
actually taste it, saliva is secreted and your
mouth will water. In this case, the secretion
represents a conditioned reflex. Conditioned
reflexes vary from one individual to another.
Reflex actions are very useful. They protect
you from harm. Blinking is a reflex that help your
eyes from objects flying the air toward your face.
Sneezing and coughing are reflexes that help to
remove objects from your throat and air
passages. The automatic action of your reflexes
usually causes you to act correctly and quickly
enough to avoid the danger threatening you.