Page 69 - Handbook of Electronic Assistive Technology

56 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

Somatosensory inputs
Visual inputs
Vestibular inputs

Postural
Control
Integrated Central Muscle responses
nervous system Muscle strength
Range of motion

FIGURE 3-2 Factors influencing postural control�

This multifaceted and dynamic control system relies on a complex interaction between
musculoskeletal, neural and sensory systems (Fig. 3-2).

The Neural System

An intact central nervous system (CNS) is key to motor and postural control systems. The
CNS is made up of the brain and the spinal cord and acts as the control centre for the body,
integrating information and input from sensory receptors and controlling motor output in
response (Fig. 3-3).
The previously believed concept that posture is primarily the result of a reflexive activ-
ity (a motor response to a sensory stimulus that occurs spontaneously and automatically
at a spinal cord level within the CNS) is now widely recognised to be incorrect. Postural
control is a much more complex process involving virtually the whole of the nervous sys-
tem (Hadders-Algra and Carlberg, 2008).
The nervous system is made up of the following:
• The spinal cord where simple reflexes occur, including automatic and stereotype
reflex movements, and the peripheral execution level of movement. Central pattern
generators for repetitive motor activities such as locomotion occur here.
• The brain stem supports the body against gravity and generates gross, stereotyped
movements and maintains equilibrium.
• The basal ganglia plays an essential role in the initiation of most activities and the
suppression of unwanted movements. It incorporates a number of feedback loops.
• The cerebrum is the main centre for the control of voluntary movement, particularly
complex motor activities such as the manipulative movement of the hand.