Touch and pain perception

A-delta fibers

myelinated nociceptors that conduct signals rapidly and respond to both heat and pressure

Afferent fibers

neural fibers that carry sensory information to the central nervous system

Ampulla

a chamber at the bottom of each semicircular canal (vestibular system), which contains a structure called the crista; also used in describing organs of electroreception

Analgesia

processes that act to reduce pain perception

Anterior cingulate cortex

a region in the prefrontal lobe of the brain associated with the emotional experience of unpleasantness during pain perception

C-fibers

nonmyelinated nociceptors that are slower and respond to pressure, extreme degrees of either heat or cold, and toxic chemicals

Cold fibers

thermoreceptors that fire in response to colder (30 °C and below) temperatures as measured on the skin

Contralateral

literally, opposite (contra) side (lateral), meaning, in this context, that sensory information is on the side of the nervous system opposite the one from which it entered

Crista

the structure in the ampulla of each semicircular canal that contains the receptors

Dermis

the inner layer of the skin, which also houses touch receptors

Dorsal

in or toward the back of the body; in the head, it means at the top or toward the top

Dorsal column–medial lemniscal pathway

a pathway for the mechanoreceptors (tactile perception) and proprioceptors (muscle position) that travels up the spinal column on the ipsilateral side and crosses to the contralateral side in the medulla

Dorsal horn

an area of the spinal cord that receives input from nociceptors and feedback from the brain

Dorsal root

the end of the spinal nerve where sensory information enters the spinal cord

Dorsal root ganglion

a node on the spine where one finds nerve cells carrying signals from sensory organs toward the somatosensory areas of the brain

Endogenous opioids

chemicals produced by the body that reduce pain throughout the body

Endolymph

fluid that fills the semicircular canals

Epidermis

the outer layer of the skin

Exploratory procedures

hand movements made in order to identify an object

FAI mechanoreceptors

fast-adapting receptors, with Meissner corpuscle endings and small receptive fields, densely packed near the surface of the skin

FAII mechanoreceptors

fast-adapting receptors with Pacinian corpuscle endings and large receptive fields, more widely distributed, deeper in the skin

Gate control theory

a model that allows for top-down control of the pain signal coming up the spinal cord

Golgi tendon organs

receptors in the tendons that measure the force of a muscle’s contraction

Haptic perception

the active use of touch to identify objects

Homunculus

a drawing of a human in which the proportions of the body parts match the relative sizes each body part has on the somatotopic map

Ipsilateral

literally, same (ipsi) side (lateral), meaning, in this context, that sensory information is on the same side of the nervous system as it entered

Joint receptors

receptors found in each joint that sense information about the angle of the joint

Macula

a structure in the vestibular system that houses the hair cells that respond to changes in head orientation (not to be confused with the region on the retina with the same name)

Mechanoreceptors

the sensory receptors in the skin that transduce physical movement on the skin into neural signals, which are sent to the brain

Meissner corpuscles

specialized transduction cells in FAI mechanoreceptors

Merkel cells

specialized transduction cells in SAI mechanoreceptors

Muscle spindles

receptors embedded in the muscles that sense information about muscle length and therefore muscle action

Nociceptive pain

pain that develops from tissue damage that causes nociceptors in the skin to fire

Nociceptors

sensory receptors in the skin that, when activated, cause us to feel pain; they are found in both the epidermis and the dermis

Otolith organs

organs responsible for detecting acceleration of the head and identifying when the head is being held at a tilted angle

Pacinian corpuscles

specialized transduction cells in FAII mechanoreceptors

Pain

the perception and unpleasant experience of actual or threatened tissue damage

Parietal insular vestibular cortex

an area in the parietal lobe that receives input from the vestibular nerve and is responsible for the perception of balance and orientation

Passive electroreception

ability by an organism to detect the electric fields generated by other animals

Proprioception

the perception of the movements and position of our limbs

Pruriceptors

receptors in our skin that respond to mild irritants by producing itch sensations

Ruffini endings

specialized transduction cells in SAII mechanoreceptors

SAII mechanoreceptors

slow-adapting receptors using Ruffini endings, with large receptive fields, more widely distributed, deeper in the skin

SAI mechanoreceptors

slow-adapting receptors using Merkel cells, with small receptive fields, densely packed near the surface of the skin

Semicircular canals

three tubes located in the inner ear responsible for the signaling of head rotation

Somatosensory cortex

an area in the parietal lobe of the cerebral cortex devoted to processing the information coming from the skin senses

Somatotopic map

a feature whereby the skin of the body maps onto the surface of the primary somatosensory cortex in a systematic way

Spinothalamic pathway

a pathway for the nociceptors (pain) and thermoreceptors (temperature) that travels up the contralateral side of the spinal column; does not synapse in the brain until the ventral posterior nucleus of the thalamus

Substantia gelatinosa

the region in the dorsal horn where neurons meet

Tactile agnosia

an inability to identify objects by touch

Thermoreception

the ability to sense changes in temperature on the skin

Thermoreceptors

the sensory receptors in the skin that signal information about the temperature as measured on the skin

Tuberous receptors

receptors used for active electroreception in those fish with this ability

Ventral

in or toward the front of the body; in the head, it means at the bottom or toward the bottom

Ventral posterior nucleus of the thalamus

an area in the thalamus that receives input from both the dorsal column–medial lemniscal pathway and the spinothalamic pathway

Ventral root

the end of the spinal cord where motor information leaves the spinal cord

Vestibular complex

a brain stem area that receives input from the vestibular nerve and sends the information to the forebrain

Vestibular system

the sensory system responsible for the perception of balance and acceleration, housed in the semicircular canals and otolith organs, both located adjacent to the inner ear

Warm fibers

thermoreceptors that fire in response to warmer temperatures (above 36 °C) as measured on the skin