Gamma Aminobutyric Acid (GAMA) A neurotransmitter of the CNS whose effects are usually inhibitory. Glial cells The supporting cells of the neural tissue.  They regulate the environment around the neurons and protect against foreign invaders. They are also known as neuroglia. Golgi Apparatus Cell organelles composed of stacks of flattened membranes containing chambers.  They synthesize, store, alter, and package secretory products and lysosomes.