Touch Sensations

Synthetic skin could bring the sensation of touch to virtual worlds
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Mechanosensation is the process by which mechanical forces are converted into electrical signals that allow people and animals to detect touch, vibrations, accelerations, and body movements. Ion channel receptors are thought to convert those forces to signals in many body systems. Previous research in mice has identified the ion channel PIEZO2 a protein in humans encoded by the PIEZO2 gene as essential for a variety of mechanosensory responses, including light touch and proprioception.

The researchers in this study identified and characterized two people ages 18 and 8 with similar skeletal deformations, severe progressive scoliosis, a unique syndrome of specific sensory problems, and who, after genetic sequencing, were found to have genetic mutations in the PIEZO2 gene.

A Touching Experience: Designing for Touch Sensations in Online Retail Environments

The researchers used various sensory tests e. The researchers observed that the participants had a selective loss of touch, but still responded to specific types of gentle mechanical stimulation on hairy skin. In addition, the participants, when not presented with visual cues, exhibited a loss of proprioception. However, the participants were able to perform a range of tasks such as walking, talking, and writing—which are generally thought to rely heavily on proprioception.

Skip to main content. Site Menu Home. Safety Information Know the Science. The skin is composed of several layers. The very top layer is the epidermis and is the layer of skin you can see. Made of dead skin cells, the epidermis is waterproof and serves as a protective wrap for the underlying skin layers and the rest of the body.

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When you are in the sun, the melanin builds up to increase its protective properties, which also causes the skin to darken. The epidermis also contains very sensitive cells called touch receptors that give the brain a variety of information about the environment the body is in. The second layer of skin is the dermis. The dermis contains hair follicles, sweat glands, sebaceous oil glands, blood vessels, nerve endings, and a variety of touch receptors.

Its primary function is to sustain and support the epidermis by diffusing nutrients to it and replacing the skin cells that are shed off the upper layer of the epidermis.

New cells are formed at the junction between the dermis and epidermis, and they slowly push their way towards the surface of the skin so that they can replace the dead skin cells that are shed. Oil and sweat glands eliminate waste produced at the dermis level of the skin by opening their pores at the surface of the epidermis and releasing the waste.

The bottom layer is the subcutaneous tissue which is composed of fat and connective tissue. The layer of fat acts as an insulator and helps regulate body temperature. It also acts as a cushion to protect underlying tissue from damage when you bump into things.

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The connective tissue keeps the skin attached to the muscles and tendons underneath. Our sense of touch is controlled by a huge network of nerve endings and touch receptors in the skin known as the somatosensory system. This system is responsible for all the sensations we feel — cold, hot, smooth, rough, pressure, tickle, itch, pain, vibrations, and more.

Within the somatosensory system, there are four main types of receptors: mechanoreceptors, thermoreceptors, pain receptors, and proprioceptors. Before we dig further into these specialized receptors, it is important to understand how they adapt to a change in stimulus anything that touches the skin and causes sensations such as hot, cold, pressure, tickle, etc. A touch receptor is considered rapidly adapting if it responds to a change in stimulus very quickly.

Basically this means that it can sense right away when the skin is touching an object and when it stops touching that object. These receptors best sense vibrations occurring on or within the skin.

The Sense of Touch

There are temporary causes of anosmia, as well, such as those caused by inflammatory responses related to respiratory infections or allergies. This finding suggests that one's own skin is the only barrier to experiencing someone else's touch sensation. The visual information from the right visual field falls on the left side of the retina and vice versa. We conclude that the final emergence and localization of touch sensations result from the coactivation and mutual inhibition of 4 systems: 1 afferents from the region touched; 2 tonic inhibition from null signals emerging from the untouched hand; 3 activation of the MNS while watching others; and 4 inhibition of MNS output, preventing it from reaching the threshold for conscious experience. Since the nucleus dorsalis does not extend into the cervical spinal cord above C8, the dorsal spinocerebellar tract does not convey information from the upper limb.

A touch receptor is considered slowly adapting if it does not respond to a change in stimulus very quickly. These receptors are very good at sensing the continuous pressure of an object touching or indenting the skin but are not very good at sensing when the stimulus started or ended. Your brain gets an enormous amount of information about the texture of objects through your fingertips because the ridges that make up your fingerprints are full of these sensitive mechanoreceptors. These mechanoreceptors can feel sensations such as vibrations traveling down bones and tendons, rotational movement of limbs, and the stretching of skin.

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This greatly aids your ability to do physical activities such as walking and playing ball. This is why your feet or hands start to go numb when they are submerged in icy water for a long period of time.

Thermoreceptors are found all over the body, but cold receptors are found in greater density than heat receptors. The highest concentration of thermoreceptors can be found in the face and ears hence why your nose and ears always get colder faster than the rest of your body on a chilly winter day. They can detect pain that is caused by mechanical stimuli cut or scrape , thermal stimuli burn , or chemical stimuli poison from an insect sting. These receptors cause a feeling of sharp pain to encourage you to quickly move away from a harmful stimulus such as a broken piece of glass or a hot stove stop.

Altered sensations

They also have receptors that cause a dull pain in an area that has been injured to encourage you not to use or touch that limb or body part until the damaged area has healed. While it is never fun to activate these receptors that cause pain, they play an important part in keeping the body safe from serious injury or damage by sending these early warning signals to the brain.

While many receptors have specific functions to help us perceive different touch sensations, almost never are just one type active at any one time. When drinking from a freshly opened can of soda, your hand can perceive many different sensations just by holding it. Thermoreceptors are sensing that the can is much colder than the surrounding air, while the mechanoreceptors in your fingers are feeling the smoothness of the can and the small fluttering sensations inside the can caused by the carbon dioxide bubbles rising to the surface of the soda.

Mechanoreceptors located deeper in your hand can sense that your hand is stretching around the can, that pressure is being exerted to hold the can, and that your hand is grasping the can. Proprioceptors are also sensing the hand stretching as well as how the hand and fingers are holding the can in relation to each other and the rest of the body. Even with all this going on, your somatosensory system is probably sending even more information to the brain than what was just described. Of course, none of the sensations felt by the somatosensory system would make any difference if these sensations could not reach the brain.

The nervous system of the body takes up this important task. Neurons which are specialized nerve cells that are the smallest unit of the nervous system receive and transmit messages with other neurons so that messages can be sent to and from the brain. This allows the brain to communicate with the body. When your hand touches an object, the mechanoreceptors in the skin are activated, and they start a chain of events by signaling to the nearest neuron that they touched something. This neuron then transmits this message to the next neuron which gets passed on to the next neuron and on it goes until the message is sent to the brain.

Now the brain can process what your hand touched and send messages back to your hand via this same pathway to let the hand know if the brain wants more information about the object it is touching or if the hand should stop touching it. Your brain just received confusing messages from your hands about what the temperature of the third glass was.