In turn, the internuncial neuron synapses with the cell body of the efferent (motor)
d. In the spinal cord, the cell bodies of the efferent (motor) neurons make up
the anterior column of the gray matter. In the brainstem, the motor neurons make up
the individual nuclei of the cranial nerves. The axon of the motor neuron passes out of
the CNS by way of the appropriate peripheral nerve. Command information is thus
carried away from the CNS.
e. The information is then delivered by the motor neuron to the effector organ.
Somatic motor neurons lead to striated muscle fibers, particularly in skeletal muscles.
Autonomic (visceral) motor neurons lead to smooth muscle tissue, cardiac muscle
tissue, or glands.
Section VII. GENERAL SENSORY PATHWAYS OF THE HUMAN
12-22. INTRODUCTION TO PATHWAYS
A pathway of the human nervous system is the series of neurons or other
structures used to transmit an item of information. In general, we consider two major
types of pathways--the general sensory pathways and the motor pathways.
a. Ascent or Descent Through the Neuraxis. The general sensory pathways
ascend through the neuraxis to the brain. The motor pathways descend through the
neuraxis from the brain. The neuraxis includes both the spinal cord and the brainstem.
The pathways are included in various fiber tracts of the neuraxis.
b. Crossing to the Opposite Side (Decussation). At some specific level in
the neuraxis, all of these pathways cross to the opposite side of the midline of the CNS.
(Each crossing is called a decussation.) Thus, the right cerebral hemisphere of the
brain communicates with the left half of the body. The left cerebral hemisphere
communicates with the right half of the body.
12-23. INTRODUCTION TO GENERAL SENSORY PATHWAYS
a. The General Senses. The general senses detect those specific stimuli
which are received throughout the body (general distribution). When these general
senses are perceived at the conscious level (in the cerebral cortex), they are known as
sensations. The general senses of humans include pain, touch, temperature, and
proprioception ("body sense").
b. Neurons of a General Sensory Pathway. A general sensory pathway
extends from the point where the stimulus is received to the postcentral gyrus of the