![]() Further, nociceptors do notĮasily adapt like many other sensory receptors. Nociceptors are stimulated whenever tissues are damaged, and the pain sensation initiates actions by the CNS to remove the source of the stimulation. They are especially abundant in the skin, the organ that is in direct contact with the external environment. Nociceptors, also referred to as pain receptors, are free nerve endings, which are widespread in body tissues, except within the nervous tissue of the brain. The signals created by these chemo- receptors are not processed within the cerebral cortex this means that the sensation created within the brain cannot be consciously detected. For example, chemoreceptors monitor changes in ion concentrations, pH, blood glucose levels, and dissolved gases. The chemoreceptors that are part of the general senses are specialized neurons used to monitor body fluids for chemical changes. These receptors do not exhibit sensory adaptation owing to their role in maintaining posture, equilibrium, and muscle tone. These receptors keep us informed about the positioning of our body or body parts while stationary or moving. Proprioceptors, such as muscle spindles and tendon organs, are used to monitor changes in skeletal muscle stretching and tendon tension during skeletal muscle contraction and relaxation. These receptors do not exhibit sensory adaptation owing to their role in regulating visceral reflexes. For example, baroreceptors within the urinary bladder will trigger the urination reflex as the bladder fills and stretches. Signals from these receptors are used to help regulate visceral reflexes such as those used to regulate blood pressure, digestion, and urination. Together these slowly adapting structures function in detecting light touch and pressure, such as when reading braille.īaroreceptors are free nerve endings that monitor stretching within distensible internal organs such as blood vessels, the stomach, and the bladder. Tactile discs in the superficial dermis are associated with tactile cells in the stratum basale of the epidermis in areas such as the fingertips, hands, lips, and external genitalia. These rapidly adapting receptors are useful in detecting the onset of light touch to the skin. Tactile (Meissner) corpuscles in the superficial dermis are most abundant in hairless areas such as fingertips, palms, and lips. ![]() The free nerve endings of the hair root plexus functions to detect hair displacement, such as when a bug lands on the forearm. These endings function primarily as pain receptors but also serve to detect touch, itch, and temperature. Free nerve endings extend from the dermis superficially to the spaces between the epidermal cells. There are several types of receptors that function in the skin as touch receptors. They are located deep in the dermis, as well as in the ligaments and tendons associated with joints. Lamellated (Pacinian) corpuscles are rapidly adapting receptors used to detect deep pressure and stretch. Pressure, touch, and stretch receptors are mechanore- ceptors (mek-ah-no-re-cep’tors), which are sensitive to mechanical stimuli displacing the tissue in which they are located.
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