Page 173 - Understanding Psychology

Figure 6.4 Voluntary and Involuntary Activities
Climbing stairs is a voluntary activity. When the pupils of your eyes get smaller after they are exposed to brighter light, this is an involuntary activity. What other involuntary activities take place in your body?
1. Review the Vocabulary List and describe the parts of the neuron.
2. Visualize the Main Idea In a diagram similar to the one below, list the divi- sions of the nervous system.
Nervous System
3. Recall Information What is the differ- ence between afferent and efferent neu- rons? What are interneurons?
4. Think Critically Marty runs in marathons. Explain the functions of Marty’s sympathetic and parasympa- thetic nervous systems during and after the race.
5. Application Activity
Put your pen or pencil down and then pick it up again. Identify and describe the parts of the nervous system that
caused those movements to happen.
speeds up the heart to hasten the supply of oxygen and nutrients to body tissues. It constricts some arteries and relaxes others so that blood flows to the muscles, where it is most needed in emergencies and strenuous activity (such as running, thereby sometimes producing a run- ner’s high). It increases the blood pressure and suspends some activi- ties, such as digestion. In contrast, the parasympathetic nervous system works to conserve energy and to enhance the body’s ability to recover from strenuous activity. It reduces the heart rate and blood pressure and helps bring the body back to its normal resting state.
All of this takes place automati-
cally. Receptors are constantly
receiving messages (hunger mes-
sages, the need to swallow or cough)
that alert the autonomic nervous sys-
tem to carry out routine activities.
Imagine how difficult it would be if
you had no autonomic nervous system and had to think about it every time your body needed to digest a sandwich or perspire.
Assessment
Chapter 6 / Body and Behavior 159