Control of Body Movement

LECTURE OUTLINE (CHAPTER 13)

LECTURE OBJECTIVES

1. Discuss the classification of neural reflexes.
2. Describe the basic components of a neural reflex.
3. Explain how some of the common spinal reflexes work and why they are important?
4. Discuss how CNS paths are precisely ordered and integrated to perform even the simpliest of voluntary behaviors.

LECTURE OUTLINE

I.  INTRODUCTION TO REFLEXES 

   A. Types of reflexes 
     1. The five components of a reflex
   B. Muscle spindles and how they work (Patellar reflex) (Animation)
     1. Muscle spindles: Intrafusal and extrafusal fibers
          a. Neural circuit involves a sensory afferent, alpha, and gamma motor neurons 
          b. Role of the CNS in muscle contraction 
                1. Alpha-gamma coactivation
     2. Golgi tendon organ
     3. How are muscle spindles and Golgi tendon organs important? 
  
II. INTEGRATION IN THE CNS

  A. Pain-induced Reflex Arcs
       1. Example 1: Withdrawal reflex
       2. Example 2: Crossed extensor reflex
  B. Central Pattern Generators: Rhythmic behaviors
       1. Examples: Breathing rhythm and walking
  C. Voluntary movements
       1. Review of brain structure and function
       2. Integration of voluntary movements
       3. Feedforward reflexes during execution of movement

Reading assignment. Please read Chapter 14 for the next lecture.


STUDY QUESTIONS ON THE CONTROL OF BODY MOVEMENT (Chapter 13)

    BASIC FACTS AND TERMS

  1. By what criteria are reflexes classified? See Table 13-1. We think of reflexes as innate and unchanging. Is that really the case? Explain and give some examples.

  2. Starting with the stimulus, outline the pathway for following (place each component in correct order):
    Patellar reflex
    Muscle spindle reflex
    Golgi tendon organ reflex
    What is the physiological significance for each of these reflexes?

  3. Define and provide the physiological significance (how or why it is important) for the following terms:
    • Central pattern generator
    • Alpha-gamma coactivation
    • Feedforward reflex
    • Corticospinal tract
    • Extrafusal fibers
    • Intrafusal fibers
    • Premotor association cortex
    • Muscle memory


    4. CONCEPTS

  4. What are autonomic (=visceral) reflexes? Although the name implies that these reflexes are involuntary, it that necessarily the case? Explain and give some examples to defend your position.

  5. You decide to flex your left thumb because it seems stiff. Starting with the thought of flexing the thumb, trace the brain and spinal pathways involved in this simple voluntary behavior. Correctly order each step. Include those parts of the central nervous system that would modulate the behavior as well as those that would provide feedback on the status of performed behavior. See Figures 9-7, 13-11, and 13-12.

  6. What part of the brain initiates a voluntary motor command? What are the roles of the basal nuclei (=basal ganglia) and the cerebellum in performing a voluntary behavior.

  7. Read about tetanus in the Running Problem for this chapter.


    8. REASONING AND PROBLEM SOLVING

  8. If you cut the gamma motor input to a stretch receptor and then stretch the muscle, what would happen, if anything? Explain your answer.

  9. If a person had a stroke that left most the cerebellum damaged, what changes in voluntary behavior might you expect?


Last revised: February 22, 2008