girl inFigure20.9is using her somatic nervous system to control the muscles needed to
play the violin. Her brain sends commands to motor neurons that move her hands so she
can play. Without the commands from her brain, she wouldn’t be able to move her hands
and play the violin.
Figure 20.9: This girl’s central nervous is controlling the movements of her hands and arms
as she plays the violin; her brain is sending commands to her somatic nervous system, which
controls the muscles of her hands and arms. ( 2 )
Theautonomic nervous systemcarriesnerveimpulsestointernalorgans. Itisresponsible
for activities that are not under your control, such as sweating and digesting food. The
autonomic nervous system has two divisions:
- Thesympathetic divisioncontrols internal organs and glands during emergencies.
It prepares the body for fight or flight (Figure20.10). For example, it increases the
heart rate and the flow of blood to the legs. - Theparasympathetic divisioncontrols internal organs and glands the rest of the
time. It manages routine functions such as digestion, heartbeat, and breathing under
normal conditions.
Remember Michael on his scooter at the start of this lesson? Why was his heart pounding
afterheregainedhisbalance? Theanswerishisautonomicnervoussystem. Thesympathetic