What is crude touch

Tactile discrimination of thickness. Johnson KO. The roles and functions of cutaneous mechanoreceptors. Lindsay RM. Role of neurotrophins and trk receptors in the development and maintenance of sensory neurons: an overview. Mountcastle VB. The columnar organization of the neocortex. Brain ; Pt. The Meissner corpuscle revised: a multiafferented mechanoreceptor with nociceptor immunochemical properties. Schmidt RF, ed.

Fundamentals of Sensory Physiology. New York: Springer-Verlag; Sinclair DC. Mechanisms of Cutaneous Sensation. New York: Oxford University Press; Retrieved Nov 13, from Explorable. The text in this article is licensed under the Creative Commons-License Attribution 4. That is it. You can use it freely with some kind of link , and we're also okay with people reprinting in publications like books, blogs, newsletters, course-material, papers, wikipedia and presentations with clear attribution.

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Damage to an individual spinal nerve produces insensitivity to vibration along the paths of the related sensory nerves. If the sensory loss results from spinal cord damage, the injury site can typically be located by walking the tuning fork down the spinal column, resting its base on the vertebral spines Martini and Welch, A number of terms are used to describe the level of sensitivity in an area of the body. Anaesthesia means a total loss of sensation — the individual cannot perceive touch, pressure, pain or temperature sensations from that area.

Allan, D. In: Montague, S. Edinburgh: Elsevier. Hancock, E. John Hopkins Magazine; 3. Marieb, E. Martini, F. Ewing, NJ: Benjamin Cummings. Sign in or Register a new account to join the discussion. You are here: Dermatology. Sense of touch: The perception of touch. Related files. Notice that although all cutaneous free nerve endings appear very similar morphologically, there are different functional types of free nerve endings, with each responding to specific types of cutaneous stimuli e.

Free nerve endings are considered to be the somatosensory receptors for pain, temperature and crude touch. Proprioceptors are located in muscles, tendons, joint ligaments and in joint capsules. There are no specialized sensory receptor cells for body proprioception 4. In skeletal striated muscle, there are two types of encapsulated proprioceptors, muscle spindles and Golgi tendon organs Figure 2.

Within the joints, there are encapsulated endings similar to those in skin, as well as numerous free nerve endings. Muscle Spindles. Muscle spindles are found in nearly all striated muscles.

A muscle spindle is encapsulated and consists of small muscle fibers, called intrafusal muscle fibers, and afferent and efferent nerve terminals Figure 2. The primary muscle spindle afferent terminates as annulospiral endings in the central area of the intrafusal muscles whereas the secondary muscle spindle afferent terminates as flower spray endings in more polar regions of intrafusal muscles.

The motor endplates of gamma motor neurons are located in the polar regions. The muscle spindle is attached to the surrounding extrastriate muscles and lays with its long axis in parallel with the long axes of the surrounding muscle. Intrafusal muscles are found exclusively in muscle spindle receptors and are distributed throughout the body among the ordinary extrafusal muscle fibers of skeletal muscles.

The intrafusal fibers are attached to the larger, surrounding extrafusal muscle fibers. They are oriented in parallel with the extrafusal fibers but do not contribute directly to muscle strength when they contract because of their small size.

There are two types of afferent terminals in the muscle spindle Figure 2. The annulospiral endings wrap around the central region of the intrafusal fibers, whereas the flower-spray endings terminate predominantly in more polar regions away from the central area of the intrafusal fibers.

In addition to afferent terminals, the terminals motor endplates of gamma motor neurons end on intrafusal muscle fibers. They will be described in detail in the chapters covering motor systems. In summary, the muscle spindles are proprioceptors specialized to monitor muscle length stretch and signal the rate of change in muscle length by changing the discharge rate of afferent action potentials. Muscle spindles are most numerous in muscles that carry out fine movements, such as the extraocular muscles and the intrinsic muscles of the hand.

There are fewer spindles in large muscles that control gross movements of the body e. The Golgi tendon organs resemble the Ruffini corpuscles. Golgi Tendon Organs. Golgi tendon organs are found in the tendons of striated extrafusal muscles near the muscle-tendon junction Figure 2.

Golgi tendon organs resemble Ruffini corpuscles. For example, they are encapsulated and contain intertwining collagen bundles, which are continuous with the muscle tendon, and fine branches of afferent fibers that weave between the collagen bundles Figure 2.

They are functionally "in series" with striated muscle. The Golgi tendon organ collagen fibers are continuous with the extrafusal muscle at one end and with the muscle tendon at its opposite end.

Consequently, the mechanical force on the organ is maximal when the extrafusal muscles contract, shorten, and increase the tension on the tendon. The Golgi tendon organ is a proprioceptor that monitors and signals muscle contraction against a force muscle tension , whereas the muscle spindle is a proprioceptor that monitors and signals muscle stretch muscle length.

Joint Receptors. Joint receptors are found within the connective tissue, capsule and ligaments of joints Figure 2. The encapsulated endings resemble the Ruffini and Pacinian corpuscles and the Golgi tendon organs.

The encapsulated receptors in the joint capsule resemble Pacinian and Ruffini endings whereas those in the ligaments resemble Golgi tendon organs. It has been suggested that information from muscles, tendons, skin and joints are combined to provide estimates of joint position and movement. For example, when the hip joint is replaced — removing all joint receptors — the ability to detect the position of the thigh relative to the pelvis is not lost. These free nerve endings are considered to be the somatosensory receptors for pain resulting from muscle, tendon, joint, or ligament damage and are not considered to be part of the proprioceptive system.

In this chapter, you have learned about somatosensory stimuli and the receptors of three components of the somatosensory systems. These three components provide accurate information about the location, shape, texture, and movement of tactile stimuli, discriminative touch , the position and movement of body parts proprioception and the application and location of painful stimuli nociception.

Tactile and proprioceptive stimuli are the mechanical forces produced when skin contacts external objects discriminative touch , limbs oppose the force of gravity body position and muscles contract and body parts move.

Painful stimuli are tissue-damaging forces. The proprioceptive receptors in muscle are also encapsulated and include the muscle spindle and Golgi tendon organ.

The joint receptors are similar to the encapsulated endings in skin and tendon and are found in the joint capsule and ligaments. The sharp cutting nociceptors are free nerve endings. Although it is convenient to subdivide somatosensory receptors and pathways for didactic, clinical and research purposes, it is important to keep in mind that most somatosensory stimuli act simultaneously and in varying degrees on all somatosensory receptors in the body part stimulated. For example, placing a heavy, cold object in an outstretched hand produces tactile, thermal, and proprioceptive sensations that allow us to appreciate the presence touch, pressure , temperature, and weight of the object and provide proprioceptive information for finger, wrist and arm adjustments so we do not drop the object.

Make the best match between the receptor type and the sensation elicited when the receptor is stimulated.