Steering and communication: Nervous system and sensory organs

Abstract

Abstract for Section 6.1: The mammalian, specifically the human nervous system is an organ which affects nearly every other system and exerts controlling, regulatory, monitoring, creative, and executive functions. It is divided into the central nervous system (CNS), which is composed of the brain (cerebrum) and the myelon (spinal cord), and the peripheral nervous system (PNS), composed of the peripheral nerves and the musculature (skeletal muscles) (Trepel 2008). Peripheral nerves are divided into cranial nerves (originate from the brain) and the spinal nerves (originate from the spinal cord). Both, the CNS and the PNS, have a motor, sensory, and autonomic division (Platzer 2005). The motor division and sensory division include a somatic and autonomic fraction. The autonomic fraction comprises the sympathetic and the parasympathetic division (see below Fig. 6.4). This chapter aims to give a short overview and basics about the developmental, anatomic, histological, and physiological aspects of a highly developed nervous system taking the human as a prototype of mammalians. Abstract for Section 6.2: A characteristic of life is the ability to react in response to a stimulus. Therefore, even primitive organisms need to be able to sense the stimulus-mostly by some kind of local excitation-transfer the information within the body, and arouse a reaction to it. Eventually this reaction will increase the chance of survival and potential reproduction and hence is highly selected for. Already single-celled protozoa are able to react to external stimuli like temperature or light. They either show a topic (approach the stimulus) or phobic reaction (flee). The movement is enabled by drift of the cytoplasm and pseudopodia. In multicellular metazoans, the site of stimulus is not necessarily the site of reaction and, therefore, conduction of information is needed.