Читать книгу Reflexology: The Definitive Practitioner's Manual: Recommended by the International Therapy Examination Council for Students and Practitoners - Beryl Crane - Страница 21

We know that any part of the skin is sensitive to touch. Touch has been used therapeutically over thousands of years. The skin is also very responsive to heat, pain and pressure, whether by touch or by other means. Even pressure from air or water brings about a responsive action in the physical body. Each and every area of the body is connected to the incredible nerve network within the brain that acts like an overseer, guiding and supervising as well as modifying the output when necessary.

Study of the body’s anatomy and physiology tells us how these nerve signals are transmitted from the specialized sensory receptors and how they respond to different stimuli. Sense organs are groups of cells that are connected to the brain or spinal cord by nerve fibres (or neurons) running along particular pathways. Those sensory nerve messages originating from the hands and the feet are received in a relatively large area in the brain’s sensory cortex compared with those from other locations, showing the innumerable nerve endings that we have in these areas. An anatomical figure (figure 2.1) depicting the size of the sensory areas in one of the paired, halves of the cerebrum that contains the sensory cortex and associated areas shows how tactile the hands and feet are. The fingertips and toes are particularly susceptible to touch because the tactile receptors called Meissner’s corpuscles are in abundance in the uppermost part of the dermis in this area of non-hairy skin. The free nerve endings found in most parts of the body enable sensations of pain, touch, pressure and temperature also to be relayed to the brain. Even hair plexuses respond to pain and touch, while Pacinian corpuscles in the dermis immediately respond to pressure and send their messages to the sensory cortex of the brain.

Figure 2.1 Anatomical figure depicting the large sensory area the hands and feet occupy in the brain

If there is a stimulus to any of the simple receptors, including all the touch, pain or pressure receptors, this sets off an electrical impulse; a strong stimulus will produce a stronger sensation – for instance, we know how a headache can develop very quickly when we stub our toe. Pain receptors in the skin are known as nociceptors: these include many of the free nerve endings found in the tissues.

The sensory nerve endings lie in the corium, the true skin; they are found within the tiny projections of this deeper layer. Each nerve fibre enters a small rounded bulb. These Pacinian corpuscles, responding to deep pressure, are abundant in the palmar surface of the hands and the plantar surface of the feet, and in all the digits, also around the tendons and ligaments. The smaller corpuscles, the tactile corpuscles of Meissner, are richly abundant in the pads of the fingertips and toes and also in the palms of the hands and soles of the feet; these are in the papillae of the skin.

Every time we stretch the tissue or muscles we contact the group of cells called the mechanoreceptors, found in the basal epidermis, in the form of Merkel’s discs. They adapt very slowly to stimulation and they trigger impulses in the sensory nervous system. The reflex action helps to adjust the tone of muscles and the activity of the internal organs. (The isometric exercises carried out during a reflexology treatment session involve active voluntary contraction of muscles without producing movement of a joint. There is also a passive exercise known as neuromuscular facilitation, used to enhance contraction or relaxation of muscles.)