1.48. Touch http://www.ck12.org
FIGURE 1.95
The spines on this cactus are like needles; they help keep away animals
that might want to eat the cactus.In some cases, messages about pain or temperature don’t travel all the way to and from the brain. Instead, they travel
only as far as the spinal cord, and the spinal cord responds to the messages by giving orders to the muscles. This
allows you to respond to pain more quickly. When messages avoid the brain in this way, it forms areflex arc, like
the one shown below (Figure1.96).
FIGURE 1.96
Reflex Arc: When a reflex hammer taps
your knee, you may immediately kick your
leg—without even thinking about it. The
nerve impulse from your knee travels to
the spinal cord, and the spinal cord sends
a message to your muscles to kick your
leg.Vocabulary
- neurons: Nerve cells.
- reflex arc: Movement of a sensory message to the spinal cord, where it transmits a response to the muscle