The CNS receives information through the sensory pathways and collates this
information against information stored in memory. This results in a decision. If the
decision is to do something, then the CNS sends out commands through the motor
We usually consider two general motor pathways--the pyramidal and the
A pyramidal motor pathway is primarily concerned with volitional (voluntary)
control of body parts, particularly with the fine movements of the hands.
The pyramidal motor pathway begins in the precentral gyrus of the cerebral
hemisphere. As we have already seen, the neurons making up the precentral and
postcentral gyri are arranged in a pattern corresponding to the various parts of the body
to which they are connected.
Immediately below the pyramids, the axons cross to the opposite side of the
CNS. Thus, the left cerebral hemisphere commands the right side of the body, and the
right cerebral hemisphere controls the left side of the body. (para 12-29)
The extrapyramidal motor pathways are concerned with automatic (nonvolitional)
control of body parts. This particularly includes patterned, sequential movements or
actions. The cerebellum plays a major role in extrapyramidal pathways. The
cerebellum is the major center for coordinating the patterned sequential actions of the
The human nervous system can be thought of as a series of steps or levels.
Each level is more complex than the level just below. No level is completely
overpowered by upper levels, but each level is controlled or guided by the next upper
level as it functions.
The simplest and lowest level of control is the reflex arc. Producing a wider
Nuclei in the medulla of the hindbrainstem control the visceral activities of the
body, such as respiration, heart beat, etc.
The reticular formation of the brainstem has a facilitory area and an inhibitory
area. This control area produces sleep or wakefulness.
The thalamus is a group of nuclei found together in the forebrainstem. The
thalamus is the major relay center of sensory inputs.
The hypothalamus is a higher control center for visceral activities of the body.