![]() ![]() ![]() Bulbous corpuscles are also present in joint capsules, where they measure stretch in the components of the skeletal system within the joint. Golgi tendon organs similarly transduce the stretch levels of tendons. In skeletal muscle tissue, these stretch receptors are called muscle spindles. Such stretch receptors can also prevent over-contraction of a muscle. For example, have you ever stretched your muscles before or after exercise and noticed that you can only stretch so far before your muscles spasm back to a less stretched state? This spasm is a reflex that is initiated by stretch receptors to avoid muscle tearing. Stretch receptors monitor the stretching of tendons, muscles, and the components of joints. Other somatosensory receptors are found in the joints and muscles. Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors. Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles. These nerve endings detect the movement of hair at the surface of the skin, such as when an insect may be walking along the skin. Follicles are also wrapped in a plexus of nerve endings known as the hair follicle plexus. Light touch is transduced by the encapsulated endings known as tactile (Meissner) corpuscles. Deep pressure and vibration is transduced by lamellated (Pacinian) corpuscles, which are receptors with encapsulated endings found deep in the dermis, or subcutaneous tissue. Merkel cells are located in the stratum basale of the epidermis. Such low frequency vibrations are sensed by mechanoreceptors called Merkel cells (figure x), also known as type I cutaneous mechanoreceptors. If you drag your finger across a textured surface, the skin of your finger will vibrate. For this reason, capsaicin can be used as a topical analgesic, such as in products such as Icy Hot™. Because of this, it will decrease the ability of other stimuli to elicit pain sensations through the activated nociceptor. The dynamics of capsaicin binding with this transmembrane ion channel is unusual in that the molecule remains bound for a long time. Capsaicin molecules bind to a transmembrane ion channel in nociceptors that is sensitive to temperatures above 37☌. For example, the sensation of heat associated with spicy foods involves capsaicin, the active molecule in hot peppers. Stressed or damaged tissues release chemicals that activate receptor proteins in the nociceptors. Mechanical, chemical, or thermal stimuli beyond a set threshold will elicit painful sensations. Nociception is the sensation of potentially damaging stimuli. Some thermoreceptors are sensitive to just cold and others to just heat. Temperature receptors are stimulated when local temperatures differ from body temperature. These two modalities use thermoreceptors and nociceptors to transduce temperature and pain stimuli, respectively. Two types of somatosensory signals that are transduced by free nerve endings are pain and temperature. There are many types of sensory receptors located in the skin, each attuned to specific touch-related stimuli. Many of the somatosensory receptors are located in the skin, but receptors are also found in muscles, tendons, joint capsules, ligaments, and in the walls of visceral organs. This means that its receptors are not associated with a specialized organ, but are instead spread throughout the body in a variety of organs (Fig.2.1.1). These modalities include pressure, vibration, light touch, tickle, itch, temperature, pain, proprioception, and kinesthesia. Somatosensation is the group of sensory modalities that are associated with touch, proprioception, and interoception. Somatosensation is considered a general sense, as opposed to the special senses discussed in this section. Know the primary categories of cutaneous senses: mechanical, thermal, and noxious. Psychological Bulletin, 138 (6), 1172–1217. doi: 10.Know that somatosensation includes touch (mechanical and thermal), pain (mechanical, thermal, chemical) & proprioception (sense of self-the topic of the next chapter). Perceptual grouping and figure–ground organization. A century of Gestalt psychology in visual perception: I. But did you see the gorilla? The problem with inattentional blindness. Neural mechanisms of visual selective attention. Roll motion stimuli: sensory conflict, perceptual weighting and motion sickness. Retrieved from ĭe Graaf, B., Bles, W., & Bos, J. Journal of Experimental Psychology: Human Perception and Performance, 6 (3), 404-412. ![]() Principles of perceptual organization and spatial distortion: the gestalt illusions. Human perception and its fascinating facts.
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