Unit 6 Introduction

The nervous system consists of an estimated 80 billion neurons with an average of 10,000 connections each. It can receive information from the external environment or the internal environment. It processes and sends information to effectors, which can cause muscles to constrict or glands to secrete hormones. The receiving, processing, and sending of information is a neuron’s specialty. Obviously, with so many neurons engaged in this activity, the brain’s capacity for higher-order functions, such as learning, memory, or language, is really remarkable.

Most medical terminology textbooks split out the “special senses” (hearing, balance, and vision). That’s a tradition in anatomy and physiology courses. We’re not going to do it that way. We’ve included special senses in this chapter because they’re still part of the nervous system and there’s a lot of overlap in the terms used.