The Central Nervous System

The Central Nervous System
Quick review
Spinal cord: a column of nerves that extends from the
brain down the back. It transmits messages between the
brain and the muscle glands in the body.
Reflex: an action that is performed as an automatic
response to stimulus.
Stimulus: a thing or event that evokes a functional
reaction in an organ or a tissue.
It’s referred to as
“central” because it
combines information from
the entire body and
coordinates activity
across the whole
➔ The brain plays a central role in the
control of most bodily functions,
including awareness, movements,
sensations, thoughts, speech, and
➔ Some reflex movements can occur via
spinal cord pathways without the
participation of brain structures.
The spinal cord is connected to a section
of the brain called the brainstem and
runs through the spinal canal.
➔ Nerve roots exit the spinal cord to both
sides of the body.
➔ The spinal cord carries signals
(messages) back and forth between the
brain and the peripheral nerves.
Many of our simple actions are reflexive. They are the
way the body protects itself from harm. Have you ever
wondered why you blink when you get a speck of dust in
your eye? Or why some people sneeze when they sneeze
These are reflexive actions designed to protect your
eyes or prevent irritants from entering your lungs.
Physicians sometimes test people’s reflexes to make
sure their nervous systems are functioning properly.
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