Figure 4.

Geometry of spines of the large apical dendrite. (A) Visual index of the spines of the large apical dendrite. Spines have been oriented to view both head and neck. The PSD region is dark gray; spine head, medium gray; and spine neck, light gray. The spines are numbered 1–77 and have not been sorted. Five spines (numbers 14, 17, 30, 53, and 60) were omitted from the simulations because they were clipped by the boundary of the reconstructed volume. Thus, the apical dendritic segment contains 72 intact spines. The scale bar is 1 μm. (B–K) Distribution of geometric parameters of the spines. (B) Total spine volume. (C) Spine head volume. The average spine head volume in the sample was 0.03 μm³. (D) Spine neck cross sectional area. (E) Base-tip length. The average spine length from the base of the spine to the apex of the head was 0.85 μm. (F) Spine neck length. (G) Base to PSD length. (H) Total surface area. (I) Head surface area. (J) Ratio of total spine surface area to total spine volume. (K) Ratio of head surface area to head volume.