1) Understand general principles underlying control of movement, including motor planning, motor performance, anticipatory postural adjustments, feedback, and reflexes
2) Describe the neuroanatomy and general functional roles of the descending systems for motor control
3) Describe the roles of the basal ganglia and cerebellum in motor control
4) Explain control of movement based on the shared interactive control from the motor systems described
OVERVIEW OF MOTOR CONTROL
The primary difference between animals and plants is the ability to move, and the organ most responsible for this difference is the brain. Some have argued, in fact, that the entire purpose of the nervous system is the control of movement. Perhaps it is no coincidence, then, that the earliest studies of neuroscience began with studies of the control of movement.
To understand the control of movement, one must first have an appreciation for the musculoskeletal system. While that is beyond the scope of this text, a few important principles are worth emphasizing before we explore in any detail what the nervous system does to control movement.
Motor Control Inherent in the Musculoskeletal System
Many of the characteristics of movements observed are dictated by the biomechanical constraints of the musculoskeletal system, which simplifies the problem of neural control.
Muscle is the source of power for movement. The nervous system must control the muscles, and therefore, some understanding of muscle physiology is required to understand neural control of movement.
The nervous system devotes considerable resources to proprioception, the conscious and subconscious sensation of the state of the muscles, and the musculoskeletal system, in order to provide accurate feedback for motor control.
The student of motor control should already possess a basic understanding of the musculoskeletal system and of muscle physiology. Proprioception is covered in Chapter 3 of this book. As we consider the systems for control of movement, we will refer back to and expand upon these concepts.
AN EXAMPLE OF A COMMON MOVEMENT TASK
What is required to sit in a chair and press a specific key on a computer keyboard, and then reach for the computer mouse (Figure 5-1)? First, we need to have the postural control system sufficient to hold our trunk and lower limbs stable in the sitting position. This will require steady, low level activation of trunk and lower limb muscles and the ability to modulate muscle activity as our body sways about in space. We will need the ability to sense body position and a sense of balance to keep upright against gravity. We would also like to be able to do this efficiently, with very little mental or physical effort.
As a person performs even a seemingly simple task, typing and then reaching for a computer mouse, a complex series of sensory and motor actions is ...