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Psychology 2e

3.3 Parts of the Nervous System

Psychology 2e3.3 Parts of the Nervous System
  1. Preface
  2. 1 Introduction to Psychology
    1. Introduction
    2. 1.1 What Is Psychology?
    3. 1.2 History of Psychology
    4. 1.3 Contemporary Psychology
    5. 1.4 Careers in Psychology
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  3. 2 Psychological Research
    1. Introduction
    2. 2.1 Why Is Research Important?
    3. 2.2 Approaches to Research
    4. 2.3 Analyzing Findings
    5. 2.4 Ethics
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  4. 3 Biopsychology
    1. Introduction
    2. 3.1 Human Genetics
    3. 3.2 Cells of the Nervous System
    4. 3.3 Parts of the Nervous System
    5. 3.4 The Brain and Spinal Cord
    6. 3.5 The Endocrine System
    7. Key Terms
    8. Summary
    9. Review Questions
    10. Critical Thinking Questions
    11. Personal Application Questions
  5. 4 States of Consciousness
    1. Introduction
    2. 4.1 What Is Consciousness?
    3. 4.2 Sleep and Why We Sleep
    4. 4.3 Stages of Sleep
    5. 4.4 Sleep Problems and Disorders
    6. 4.5 Substance Use and Abuse
    7. 4.6 Other States of Consciousness
    8. Key Terms
    9. Summary
    10. Review Questions
    11. Critical Thinking Questions
    12. Personal Application Questions
  6. 5 Sensation and Perception
    1. Introduction
    2. 5.1 Sensation versus Perception
    3. 5.2 Waves and Wavelengths
    4. 5.3 Vision
    5. 5.4 Hearing
    6. 5.5 The Other Senses
    7. 5.6 Gestalt Principles of Perception
    8. Key Terms
    9. Summary
    10. Review Questions
    11. Critical Thinking Questions
    12. Personal Application Questions
  7. 6 Learning
    1. Introduction
    2. 6.1 What Is Learning?
    3. 6.2 Classical Conditioning
    4. 6.3 Operant Conditioning
    5. 6.4 Observational Learning (Modeling)
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  8. 7 Thinking and Intelligence
    1. Introduction
    2. 7.1 What Is Cognition?
    3. 7.2 Language
    4. 7.3 Problem Solving
    5. 7.4 What Are Intelligence and Creativity?
    6. 7.5 Measures of Intelligence
    7. 7.6 The Source of Intelligence
    8. Key Terms
    9. Summary
    10. Review Questions
    11. Critical Thinking Questions
    12. Personal Application Questions
  9. 8 Memory
    1. Introduction
    2. 8.1 How Memory Functions
    3. 8.2 Parts of the Brain Involved with Memory
    4. 8.3 Problems with Memory
    5. 8.4 Ways to Enhance Memory
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  10. 9 Lifespan Development
    1. Introduction
    2. 9.1 What Is Lifespan Development?
    3. 9.2 Lifespan Theories
    4. 9.3 Stages of Development
    5. 9.4 Death and Dying
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  11. 10 Emotion and Motivation
    1. Introduction
    2. 10.1 Motivation
    3. 10.2 Hunger and Eating
    4. 10.3 Sexual Behavior
    5. 10.4 Emotion
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  12. 11 Personality
    1. Introduction
    2. 11.1 What Is Personality?
    3. 11.2 Freud and the Psychodynamic Perspective
    4. 11.3 Neo-Freudians: Adler, Erikson, Jung, and Horney
    5. 11.4 Learning Approaches
    6. 11.5 Humanistic Approaches
    7. 11.6 Biological Approaches
    8. 11.7 Trait Theorists
    9. 11.8 Cultural Understandings of Personality
    10. 11.9 Personality Assessment
    11. Key Terms
    12. Summary
    13. Review Questions
    14. Critical Thinking Questions
    15. Personal Application Questions
  13. 12 Social Psychology
    1. Introduction
    2. 12.1 What Is Social Psychology?
    3. 12.2 Self-presentation
    4. 12.3 Attitudes and Persuasion
    5. 12.4 Conformity, Compliance, and Obedience
    6. 12.5 Prejudice and Discrimination
    7. 12.6 Aggression
    8. 12.7 Prosocial Behavior
    9. Key Terms
    10. Summary
    11. Review Questions
    12. Critical Thinking Questions
    13. Personal Application Questions
  14. 13 Industrial-Organizational Psychology
    1. Introduction
    2. 13.1 What Is Industrial and Organizational Psychology?
    3. 13.2 Industrial Psychology: Selecting and Evaluating Employees
    4. 13.3 Organizational Psychology: The Social Dimension of Work
    5. 13.4 Human Factors Psychology and Workplace Design
    6. Key Terms
    7. Summary
    8. Review Questions
    9. Critical Thinking Questions
    10. Personal Application Questions
  15. 14 Stress, Lifestyle, and Health
    1. Introduction
    2. 14.1 What Is Stress?
    3. 14.2 Stressors
    4. 14.3 Stress and Illness
    5. 14.4 Regulation of Stress
    6. 14.5 The Pursuit of Happiness
    7. Key Terms
    8. Summary
    9. Review Questions
    10. Critical Thinking Questions
    11. Personal Application Questions
  16. 15 Psychological Disorders
    1. Introduction
    2. 15.1 What Are Psychological Disorders?
    3. 15.2 Diagnosing and Classifying Psychological Disorders
    4. 15.3 Perspectives on Psychological Disorders
    5. 15.4 Anxiety Disorders
    6. 15.5 Obsessive-Compulsive and Related Disorders
    7. 15.6 Posttraumatic Stress Disorder
    8. 15.7 Mood Disorders
    9. 15.8 Schizophrenia
    10. 15.9 Dissociative Disorders
    11. 15.10 Disorders in Childhood
    12. 15.11 Personality Disorders
    13. Key Terms
    14. Summary
    15. Review Questions
    16. Critical Thinking Questions
    17. Personal Application Questions
  17. 16 Therapy and Treatment
    1. Introduction
    2. 16.1 Mental Health Treatment: Past and Present
    3. 16.2 Types of Treatment
    4. 16.3 Treatment Modalities
    5. 16.4 Substance-Related and Addictive Disorders: A Special Case
    6. 16.5 The Sociocultural Model and Therapy Utilization
    7. Key Terms
    8. Summary
    9. Review Questions
    10. Critical Thinking Questions
    11. Personal Application Questions
  18. References
  19. Index

Learning Objectives

By the end of this section, you will be able to:
  • Describe the difference between the central and peripheral nervous systems
  • Explain the difference between the somatic and autonomic nervous systems
  • Differentiate between the sympathetic and parasympathetic divisions of the autonomic nervous system

The nervous system can be divided into two major subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS), shown in Figure 3.13. The CNS is comprised of the brain and spinal cord; the PNS connects the CNS to the rest of the body. In this section, we focus on the peripheral nervous system; later, we look at the brain and spinal cord.

Image (a) shows an outline of a human body with the brain and spinal cord illustrated. Image (b) shows an outline of a human body with a network of nerves depicted.
Figure 3.13 The nervous system is divided into two major parts: (a) the Central Nervous System and (b) the Peripheral Nervous System.

Peripheral Nervous System

The peripheral nervous system is made up of thick bundles of axons, called nerves, carrying messages back and forth between the CNS and the muscles, organs, and senses in the periphery of the body (i.e., everything outside the CNS). The PNS has two major subdivisions: the somatic nervous system and the autonomic nervous system.

The somatic nervous system is associated with activities traditionally thought of as conscious or voluntary. It is involved in the relay of sensory and motor information to and from the CNS; therefore, it consists of motor neurons and sensory neurons. Motor neurons, carrying instructions from the CNS to the muscles, are efferent fibers (efferent means “moving away from”). Sensory neurons, carrying sensory information to the CNS, are afferent fibers (afferent means “moving toward”). A helpful way to remember this is that efferent = exit and afferent = arrive. Each nerve is basically a bundle of neurons forming a two-way superhighway, containing thousands of axons, both efferent and afferent.

The autonomic nervous system controls our internal organs and glands and is generally considered to be outside the realm of voluntary control. It can be further subdivided into the sympathetic and parasympathetic divisions (Figure 3.14). The sympathetic nervous system is involved in preparing the body for stress-related activities; the parasympathetic nervous system is associated with returning the body to routine, day-to-day operations. The two systems have complementary functions, operating in tandem to maintain the body’s homeostasis. Homeostasis is a state of equilibrium, or balance, in which biological conditions (such as body temperature) are maintained at optimal levels.

A diagram of a human body lists the different functions of the sympathetic and parasympathetic nervous system. The parasympathetic system can constrict pupils, stimulate salivation, slow heart rate, constrict bronchi, stimulate digestion, stimulate bile secretion, and cause the bladder to contract. The sympathetic nervous system can dilate pupils, inhibit salivation, increase heart rate, dilate bronchi, inhibit digestion, stimulate the breakdown of glycogen, stimulate secretion of adrenaline and noradrenaline, and inhibit contraction of the bladder.
Figure 3.14 The sympathetic and parasympathetic divisions of the autonomic nervous system have the opposite effects on various systems.

The sympathetic nervous system is activated when we are faced with stressful or high-arousal situations. The activity of this system was adaptive for our ancestors, increasing their chances of survival. Imagine, for example, that one of our early ancestors, out hunting small game, suddenly disturbs a large bear with her cubs. At that moment, his body undergoes a series of changes—a direct function of sympathetic activation—preparing him to face the threat. His pupils dilate, his heart rate and blood pressure increase, his bladder relaxes, his liver releases glucose, and adrenaline surges into his bloodstream. This constellation of physiological changes, known as the fight or flight response, allows the body access to energy reserves and heightened sensory capacity so that it might fight off a threat or run away to safety.

While it is clear that such a response would be critical for survival for our ancestors, who lived in a world full of real physical threats, many of the high-arousal situations we face in the modern world are more psychological in nature. For example, think about how you feel when you have to stand up and give a presentation in front of a roomful of people, or right before taking a big test. You are in no real physical danger in those situations, and yet you have evolved to respond to a perceived threat with the fight or flight response. This kind of response is not nearly as adaptive in the modern world; in fact, we suffer negative health consequences when faced constantly with psychological threats that we can neither fight nor flee. Recent research suggests that an increase in susceptibility to heart disease (Chandola, Brunner, & Marmot, 2006) and impaired function of the immune system (Glaser & Kiecolt-Glaser, 2005) are among the many negative consequences of persistent and repeated exposure to stressful situations. Some of this tendency for stress reactivity can be wired by early experiences of trauma.

Once the threat has been resolved, the parasympathetic nervous system takes over and returns bodily functions to a relaxed state. Our hunter’s heart rate and blood pressure return to normal, his pupils constrict, he regains control of his bladder, and the liver begins to store glucose in the form of glycogen for future use. These restorative processes are associated with activation of the parasympathetic nervous system.

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