Chapter 3 tb notes (leave out: 82-85, 92-98, 112-120. Nervous system is living tissue composed of cells. Soma, or cell body: contains the cell nucleus and much of the chemical machinery common to most (cid:272)ells; the rest of the (cid:374)euro(cid:374) is de(cid:448)oted e(cid:454)(cid:272)lusi(cid:448)el(cid:455) to ha(cid:374)dli(cid:374)g i(cid:374)for(cid:373)atio(cid:374)"s. Dendrites: (the branches on the neurons) are the parts of a neuron that are specialized to receive information. Axons are wrapped in cells with a high concentration of a white, fatty substance called myelin. Myelin sheath: insulating material, derived from glial cells, that encases some axons; speeds up the transmission of signals that move along axons. The axons end in cluster of terminal buttons: small knobs that secrete chemicals called neurotransmitters; these chemicals serve as messengers that may activate neighbouring neurons. The points at which neurons interconnect are called synapses: junction where information is transmitted from one neuron to another.