Page 345 - Atlas of Histology with Functional Correlations

represent the ascending and descending neural pathways of the spinal cord. The

axons (4) of the anterior horn motor neurons aggregate into groups, pass through
the white matter, and exit the spinal cord as the anterior (ventral) root fibers (see
Fig. 9.5).

FIGURE 9.6 ■ Spinal cord: anterior gray horn, motor neurons, and adjacent
anterior white matter. Stain: silver impregnation (Cajal method). Medium
magnification.

FIGURE 9.7 | Ultrastructure of Typical

Axodendritic Synapses in the CNS

It is not possible to see synapses in the CNS with routine hematoxylin and eosin

preparations. This high-magnification transmission electron micrograph shows
two typical axodendritic synapses (2, 4) in the CNS. The terminal end of the
presynaptic component (1, 3) is expanded and contains numerous small
neurotransmitter vesicles (1, 3). A small intercellular space, called the

synaptic cleft (2, 4), is located between and separates the presynaptic
membrane (2, 4) from the postsynaptic membranes (8). The postsynaptic
membranes (8) appear thicker and denser than the presynaptic membrane (2, 4).
In the center of the image is a section of a dendrite (7) with neurofilaments,

microtubules, and large mitochondria (7). Located around the dendrite (7) are
smaller myelinated axons (5) with a dense, thick myelin sheath (9). In the
upper region of the figure are numerous unmyelinated axons (6). Both the
myelinated axons (5) and the unmyelinated axons (6, 7) contain dark-staining,

oval mitochondria (6) with shelflike cristae.

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