Homeostatic and Psychological Bases of Eating and Drinking

Abstract

Eating and drinking are examples of behaviours that illustrate the stimulus-response model of perception (Fig. 3.7). Communication processes rely, in the first instance, on the presence of sensors capable of receiving signals from the environment. In living organisms, the so-called autonomic senses respond to metabolic stimuli, whereas external stimuli are received by sensors located in specialised sense organs, such as the eye. In the case of the autonomic senses, the cognitive stages of the stimulus-response model are omitted. The autonomic and special senses together collect information to allow various systems within the organism to respond to stimuli in an appropriate, life-supporting manner. In interpreting sensory experiences involving the special senses, the brain refers to past events as well as contextual factors. In this case, the individual has at least some control over what is being experienced, and how the experience is interpreted. This is in contrast to the autonomic senses, which cannot normally be influenced through thinking power. Mechanisms such as body temperature regulation, water and electrolyte balance and the maintenance of blood glucose levels are typical of those involving the autonomic senses. Stimulation of the special senses and, in some cases, of the autonomic senses may be subject to classical conditioning, which is also known as Pavlovian conditioning [8]. Classical conditioning plays a pervasive role in the regulation of eating behaviours. Conditioned stimuli paired with individual foods, or with defined eating patterns, have the ability to elicit motivational states, in particular, appetite and satiety. Appetite may be elicited through a glance at one’s watch, which may tell one that lunchtime is approaching, with all the associated imaginings and anticipations. Similarly, satiety may be elicited by eating one’s dessert at the end of a multi-course meal. This provides the signal that a meal, which has also been a “proper” meal, has been suitably concluded. Food aversions are also commonly acquired via mechanisms related to classical conditioning.