Sensory Systems and Neural Components of Pain

Flashcards on Sensory Systems and Pain

Somatosensation

Sensory information from the skin and musculoskeletal systems, including cutaneous information (touch, nociception, temperature) and information from the musculoskeletal system (proprioception and nociception).

First-order neuron

Neuron in the somatosensory pathway that conveys information from sensory receptors to the spinal cord or brainstem.

Second-order neuron

Neuron in the somatosensory pathway that conveys information from the spinal cord or brainstem to the thalamus.

Third-order neuron

Neuron in the somatosensory pathway that conveys information from the thalamus to the cerebral cortex.

Mechanoreceptors

Sensory receptors that respond to mechanical deformation by touch, pressure, stretch, or vibration. They are associated with free nerve endings or specialized end-organs.

Chemoreceptors

Sensory receptors that respond to exogenous chemicals or substances released by cells, including damaged cells after injury or infection. They are associated with free nerve endings.

Thermoreceptors

Sensory receptors that respond to heat or cooling. They are associated with free nerve endings.

Proprioceptors

Sensory receptors including muscle spindles, Golgi tendon organs and joint receptors that provide information about body position, muscle stretch, and tension.

Muscle Spindles

Sensory organs embedded in muscle that respond to stretch, both change in muscle length and velocity of length change.

Golgi Tendon Organs

Encapsulated nerve endings woven among collagen strands of the tendon, sensitive to slight changes in tension on a tendon.

Joint Receptors

Receptors located in joint capsules and ligaments, that respond to mechanical changes of joint capsules and ligaments.

Tactile Receptors

Sensory receptors, including free nerve endings, Meissner’s corpuscles, Pacinian corpuscles, Ruffini corpuscles, hair follicle nerve endings and Merkel cells that relay touch, pressure, and vibration information from the skin.

Nociception

Neural feedback that allows the central nervous system (CNS) to detect and avoid noxious and potentially damaging stimuli.

Dermatomes

Area of skin innervated by axons that enter the spinal cord through a single dorsal root; used to diagnose radiculopathy and to determine the sensory level affected by spinal cord injury.

Peripheral nerves

Connect motor or sensory end-organs with the CNS and can regenerate at a rate of 1 mm/day.

DCML

Dorsal Column Medial Lemniscus pathway carries information regarding light touch, vibration, and conscious proprioception.

ALS

Anterolateral system (pathways that run on anterolateral columns)

Spinothalamic Pathway

Carries information regarding nociception, temperature, and crude touch.

Gate Theory

Collateral branches of light touch afferents synapse with interneurons that inhibit nociceptive projection neurons within the dorsal horn; Using light touch, pressure, vibration, etc to alleviate pain is applying gate theory

Acute Pain

Typically lasts for a short perior of time; Resolves after noxious stimulus is removed or tissue injury heals; Detected by nociceptors

Chronic Pain

Lasts or recurs for longer than 3 months

Central Sensitization

Increased of function in the central nociceptive system. Common chronic primary pain syndromes are primarily due to central sensitization

Complex Regional Pain Syndrome

Syndrome of pain, vascular changes, and atrophy. Typical signs and symptoms are worst in distal extremity, often in a stocking or glove distribution

Neuropathic Pain

“pain arising as a direct consequence of a lesion or disease affecting the somatosensory system” – The International Association for the Study of Pain

Phantom Pain

Phantom sensation that is painful, felt in the missing part of the limb.