Question

In heman being a typical nerve cell is
Bipolar
Apolas
O Multipola
pseudounipolar​

Answer 1

Answer:

Dorsal Root Entry Zone and Bifurcation Zone

Each dorsal root ganglion pseudounipolar neuron has a protrusion that reaches into the spinal cord. Depending on entry level, their protrusions are placed into the gracile or cuneate fascicle organizing a well-known somatotopy in the dorsal funiculi (see for humans: Marani and Schoen, 2005, and references therein).

During the development of the rat spinal cord dorsally above the dorsal root entry zone (DREZ) a dorsal root bifurcation (DRB) area can be distinguished. At E16 the bifurcation zone changes into the dorsal funiculus, due to medial displacement. CD15 (= SSEA-1) characterizes at E13 the DREZ while the DRB stays negative (Oudega et al., 1993). The shift of the DRB towards the position of the mature dorsally placed gracilis and cuneatus fasciculus supports the construction of the human dorsal columns according to Peerbolte (1932, Figure 4.13A), based on the immunocytological localization of microtubule-associated proteins 1A (Oudega et al.,1993; see also for the mature spinal cord Miller and Basbaum, 1975; Voogd, 1998, 2008).

FIGURE 4.13. Somatotopy organization in the dorsal columns. (A) Organization according to Litaert Peerbolte (1932; with permission from Dr J.Voogd). (B) Organization according to Winkler (1917).

The more or less layered representation of the dermatomes in the dorsal columns is favored by Smith and Deacon (1984, see Figure 4.13B) and is generally accepted (see Feirabend et al., 2002). The discussion on the organization of the somatotopy in the dorsal columns is still important for the areas that can be reached by spinal cord stimulation (see part models and stimulation of PNS).