Sensory systems touch

Like taste, touch is a combination of sensory systems that are expressed in a common organ—in this case, the skin. The detection of pressure and the detection of temperature are two key components. Amiloride-sensitive sodium channels, homologous to those of taste, appear to play a role. Other systems are responsible for detecting painful stimuli such as high temperature, acid, or certain specific chemicals. Although our understanding of this sensory system is not as advanced as that of the other sensory systems, recent work has revealed a fascinating relation between pain and taste sensation, a relation well known to anyone who has eaten "spicy" food. 

Energy and information. The transmission of sensory information requires the input of free energy. For each sensory system (olfaction, gustation, vision, hearing, and touch), identify mechanisms for the input of free energy that allow the transmission of sensory information. 

Effects observed in humans following neurotoxic exposure include modification of motor and sensory activities, emotional states, integrative capabilities such as learning and memory, adverse effects on sensory systems (including sight, hearing, smell, touch, and pain sensation), behavior modification, sleep loss, speech impairment, delirium, hallucinations, convulsions, and deaths1-4 ... 

How do our sensory systems work How are the initial stimuli detected How are these initial biochemical events transformed into perceptions and experiences We have already encountered systems that sense and respond to chemical signals—namely, receptors that bind to growth factors and hormones. Our knowledge of these receptors and their associated signal-transduction pathways provides us with concepts and tools for unraveling some of the workings of sensory systems. For example, 7TM receptors (seven-transmembrane receptors. Section 14.1) play key roles in olfaction, taste, and vision. Ion channels that are sensitive to mechanical stress are essential for hearing and touch. 

Smell, taste, vision, hearing, and touch are based on signal-transduction pathways activated by signals from the environment. These sensory systems function similarly to the signal-transduction pathways for many hormones. "These intercellular signaling pathways appear to have been appropriated and modified to process environmental information. 

This chapter will consider methods and devices used to present visual, auditory, and tactual (touch) information to persons with sensory deficits. Sensory atigmentation systems such as eyeglasses and hearing aids enhance the existing capabilities of a functional human sensory system. Sensory substitution is the use of one human sense to receive information normally received by another sense. Braille and speech synthesizers are examples of systems that substitute touch and hearing, respectively, for information that is normally visual (printed or displayed text). 

We begin by describing the mechanisms of how muscles work as a part of a prosthesis in the context of a robotic artificial hand. The same issue can be extended to other prostheses that have been brought up by many different researchers in the field. The nervous system has specific sensory systems, one of which is the feeling of touch, which is a perception that naturally results from activation of neural receptors on the skin. Receptors detect stimulus, converting into information and directing to the central nervous system by afferent neurons. 

Olfactory system is unique in that there are numerous receptors for each specific kind of odorants [91]. It is very peculiar compared to other sensory systems like vision, touch, or taste in which only a few kinds of receptors exist. Eugenol has a very distinctive odor that is usually remembered as dental clinic scent. The olfactory receptor that eugenol binds was identified in mice and named mOR-EG or 01fr73, a G-protein-coupled receptor with a seven-transmembrane domain that increases intracellular cAMP concentration upon activation [92]. 

Human skin is a fascinating example of a large area sensory system, allowing us to sense temperature, humidity, touch, pressure, and vibration. Scientists are inspired by this natural model system and work on artificial electronic sensor surfaces (Lacour et al. 2005) that will ultimately enable robots with a sense of feeling (Chortos and Bao 2014 Hammock et al. 2013 Bauer et al. 2014). A full coverage of this topic is beyond the scope of this chapter, so here we focus on illustrating the huge potential for piezoelectric polymers in electronic skin development with two selected researeh examples. 

A second difficulty in studying the brain mechanisms of flavor is that the flavor modality is large and ill defined. One can appreciate this by considering other sensory systems. Visual perception is characterized by the specific attributes of a visual stimulus—wavelength, luminance, shape, orientation, motion. Similarly, hearing is characterized by the specific qualities of sound frequency, loudness, and frequency modulation. Touch is characterized by place, quality, and intensity. In all these cases what we may call the sensory space is clearly limited and clearly defined. 

The sensory system is highly sensitive and therefore may dominate the picture. Sensory loss usually involves touch, pain and temperature modalities. These can be limited to cervical areas uni- or bilaterally. 

Peripheral nervous system Nerve tissues lying outside the brain and spinal cord, functions include the transmittal of sensory information such as touch, heat, cold, and pain, and the motor impulses for limb movement. 

Association of Pain, neuropathic pain is defined as pain initiated or caused by a primary lesion, dysfunction in the nervous system". Neuropathy can be divided broadly into peripheral and central neuropathic pain, depending on whether the primary lesion or dysfunction is situated in the peripheral or central nervous system. In the periphery, neuropathic pain can result from disease or inflammatory states that affect peripheral nerves (e.g. diabetes mellitus, herpes zoster, HIV) or alternatively due to neuroma formation (amputation, nerve transection), nerve compression (e.g. tumours, entrapment) or other injuries (e.g. nerve crush, trauma). Central pain syndromes, on the other hand, result from alterations in different regions of the brain or the spinal cord. Examples include tumour or trauma affecting particular CNS structures (e.g. brainstem and thalamus) or spinal cord injury. Both the symptoms and origins of neuropathic pain are extremely diverse. Due to this variability, neuropathic pain syndromes are often difficult to treat. Some of the clinical symptoms associated with this condition include spontaneous pain, tactile allodynia (touch-evoked pain), hyperalgesia (enhanced responses to a painful stimulus) and sensory deficits. 

Sensation provides the input to the system. The sources of sensory information can be outside your body through one of the five primary senses sight, sound, taste, smell, and touch. The source of information can also be inside your body. The nervous system receives and monitors information such as your blood pressure, blood sugar, and blood oxygen level. 

The human body, for instance, has sensors (eyes, ears, touch receptors in the skin, and so forth), a controller (the brain), and actuators (muscles) to react and respond to commands. These are the same basic concepts as the adaptive systems discussed in this chapter. Robots today, such as the welding machines used in industry or the toy dogs sold as pets, are extremely Umited in mobility and adaptability compared to humans. Yet smart materials, along with a design based on the sensory, nervous, and muscular systems of the body, could one day create an agile and adaptable robot. 

As a sensory structure. The skin contains receptors providing information about our surroundings and changes in the environment. The receptors are part of the nervous system and those in the skin are sensitive to touch,... 

Somatic versus autonomic. The somatic nervous system comprises functions that are conscious - conscious sensations such as touch, temperature, pain etc., and voluntary movements. Conversely, the autonomic nervous system deals with unconscious sensory input such as blood pressure, blood oxygen and carbon dioxide lev-els and the likewise unconscious regulatory responses to it. 

Uses.—It is necessary to distinguish clearly between the local and systemic effects of cocaine. When locally applied cocaine is a paralyzant to the peripheral ends of the sensory nerves, and to a lesser degree to the motor nerves, and stimulating to the muscular coats of the blood vessels. As a result of these actions when painted over mucous membranes it causes blanching of the part and diminished sensation. It produces not only lessened serisibility to pain and touch but also of the acuity of the special senses, thus it diminishes in the mouth the power of taste and in the nose that of smell. 

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