1. Acetylcholine is the most common. Neurons that release it are called cholinergic. Cholinergic neurons include all preganglionic neurons of the autonomic nervous system, postganglionic neurons of the parasympathetic nervous system and some postganglionic neurons (sweat glands) of the sympathetic nervous system.cetylcholine is the most common. Neurons that release it are called cholinergic. Cholinergic neurons include all preganglionic neurons of the autonomic nervous system, postganglionic neurons of the parasympathetic nervous system and some postganglionic neurons (sweat glands) of the sympathetic nervous system.
Translocation is the movement of materials from leaves to other tissues throughout the plant. Plants produce carbohydrates (sugars) in their leaves by photosynthesis, but nonphotosynthetic parts of the plant also require carbohydrates and other organic and nonorganic materials.t is pressure, generated in the sieve elements and companion cells in source tissues. In leaves, sugar is synthesized in mesophyll cells (the middle layer of the leaf), and is then actively pumped into the phloem, using metabolic energy.
1 Sugar diffuses from the mesophyll in the leaf to the phloem cells in the vascular bundles. 2  Specialized cells called companion cells load the dissolved sugar into the sugar-conducting cells (called sieve elements) of the phloem by using cellular ATP as an energy source. - collections of similar cells that serve a specific purpose by functioning together. 2  Unlike animals, the major organs of plants (roots, stems, and leaves) are all composed of the same three tissues (epidermis, vascular tissues, and ground tissues).