#Free nerve endings function skin
#Free nerve endings function free

A fifth type of mechanoreceptor, Krause end bulbs, are found only in specialized regions.

#Free nerve endings function skin

They contain mechanically gated ion channels whose gates open or close in response to pressure, touch, stretching, and sound.” There are four primary tactile mechanoreceptors in human skin: Merkel’s disks, Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscle two are located toward the surface of the skin and two are located deeper. Mechanoreceptors sense stimuli due to physical deformation of their plasma membranes. There are three classes of mechanoreceptors: tactile, proprioceptors, and baroreceptors. They are slow to adjust to a stimulus and so are less sensitive to abrupt changes in stimulation.

#Free nerve endings function free

Free nerve endings are sensitive to painful stimuli, to hot and cold, and to light touch. Free nerve endings are the most common nerve endings in skin, and they extend into the middle of the epidermis. A free nerve ending, as its name implies, is an unencapsulated dendrite of a sensory neuron. Mechanoreceptors in the skin are described as encapsulated (that is, surrounded by a capsule) or unencapsulated (a group that includes free nerve endings). What is commonly referred to as “touch” involves more than one kind of stimulus and more than one kind of receptor. These categories are based on the nature of stimuli each receptor class transduces. Sensory receptors are classified into five categories: mechanoreceptors, thermoreceptors, proprioceptors, pain receptors, and chemoreceptors. (credit: modification of work by Don Bliss, National Cancer Institute) Mammalian skin has three layers: an epidermis, a dermis, and a hypodermis.

The hypodermis, which holds about 50 percent of the body’s fat, attaches the dermis to the bone and muscle, and supplies nerves and blood vessels to the dermis. Below the epidermis and dermis is the subcutaneous tissue, or hypodermis, the fatty layer that contains blood vessels, connective tissue, and the axons of sensory neurons. Below this, the much thicker dermis contains blood vessels, sweat glands, hair follicles, lymph vessels, and lipid-secreting sebaceous glands ( Figure 17.4). The epidermis serves as a barrier to water and to invasion by pathogens. It is relatively thin, is composed of keratin-filled cells, and has no blood supply. Recall that the epidermis is the outermost layer of skin in mammals. A variety of receptor types-embedded in the skin, mucous membranes, muscles, joints, internal organs, and cardiovascular system-play a role.

Somatosensation occurs all over the exterior of the body and at some interior locations as well. Somatosensation is also known as tactile sense, or more familiarly, as the sense of touch. Somatosensation is a mixed sensory category and includes all sensation received from the skin and mucous membranes, as well from as the limbs and joints.

Explain why the perception of pain is subjective.

Describe the topographical distribution of somatosensory receptors between glabrous and hairy skin.

Describe four important mechanoreceptors in human skin.