尤其是在科普读物读物中.我理解"组织"一词在这里可能和医学上对"组织"的定义不一样. 全当"脑组织"一说是一种通俗称法,没有谁会在上面学究.这种事例很多,如医学上只有源于上皮组织的恶性肿瘤才叫癌,但普通人将任何一种恶性肿瘤都叫癌.

组织学(Histology)上对组织,器官,系统是有严格的界定.组织只有四种,其中包括神经组织,没有脑组织这个类别.大脑是器官,除主要构成成分神经组织外, 还有上皮组织和血管等.

From Wikipedia
The blood-brain barrier (abbreviated BBB, also known as the blood-cerebrospinal fluid barrier) is a membrane that controls the passage of substances from the blood into the central nervous system.

Animal tissues
There are four basic types of tissue in the body of all animals, including the human body and lower multicellular organisms such as insects. These compose all the organs, structures and other contents.

Epithelium - Tissues composed of layers of cells that cover organ surfaces such as surface of the skin and inner lining of digestive tract. The tissues serve for protection, secretion, and absorption.
Connective tissue - As the name suggests, connective tissue holds everything together. Blood is considered a connective tissue. These tissues contain extensive extracellular matrix.
Muscle tissue - Muscle cells contain contractile filaments that move past each other and change the size of the cell. Muscle tissue also is separated into three distinct categories: visceral or smooth muscle, which is found in the inner linings of organs; skeletal muscle, which is found attached to bone in order for mobility to take place; and cardiac muscle which is found in the heart.
Nervous tissue - Cells forming the brain, spinal cord and peripheral nervous system.