Term
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Definition
| neurons in the dorsal root ganglia; peripheral & central components of afferent fibers are continuous, attached to the cell body in the ganglia by a single process |
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Definition
| the process of converting the energy of a stimulus into an electrical signal |
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| receptor potential (AKA generator potential) |
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Definition
| a depolarizing current generated by the alteration of the permeability of cation channels in afferent nerve endings due to a stimulus |
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Definition
| specialized receptor cells that often encapsulate afferent fibers; help tune the afferent fiber to particular features of somatic sensation |
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Definition
| afferent fibers that lack specialized receptor cells; especially important in the sensation of pain |
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Definition
| the largest-diameter sensory afferents; supply the sensory receptors in the muscles; make primary endings; largest myelinated sensory axons |
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Definition
| afferents that convey most of the information subserving tough; slightly smaller diameter fibers than Ia |
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Definition
| convey information about pain & temperature; small diameter fibers |
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Definition
| the area of the skin surface over which stimulation results in a significant change in the rate of action potentials; used to distinguish sensory afferents |
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Definition
| the minimum interstimulus distance required to perceive two simultaneously applied stimuli as distinct; varies dramatically across the skin surface |
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Term
| rapidly adapting afferents |
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Definition
| those that become dormant in the face of continued stimulus; particularly effective in conveying information about changes in ongoing stimulation such as those produced by stimulus movement |
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Term
| slowly adapting afferents |
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Definition
| better suited to provide information about the spatial attributes of the stimulus such as size & shape; opposite of rapidly adapting afferents |
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Definition
| active touching; involves the interpretation of complex spatiotemporal patterns of stimuli that are likely to activate many classes of machanoreceptors |
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Definition
| a capacity by which manipulating an object with the hand can often provide enough information to identify the object |
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Definition
| slowly adapting fibers that account for about 25% of the mechanosensory afferents in the hand; in the fingertips; only afferents to sample information from receptor cells located in the epidermis |
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Definition
| rapidly adapting fibers that innervate the skin even more densely than Merkel afferents; account for about 40% of the mechanosensory innervation of the human hand; formed by a connective tissue capsule that comprises several lamellae of Schwann cells |
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Definition
| rapidly adapting fibers that make up 10-15% of the mechanosensory innervation in the hand; located deep in the dermis or in the subcutaneous tissue; resembles a small onion (concentric layers of membranes surrounding a single afferent fiber) |
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Definition
| slowly adapting fibers; least understood of the cutaneous mechanoreceptors; elongated, spindle-shaped, capsular specializations |
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Definition
| found in all but a few skeletal muscles; give the most detailed knowledge about proprioception |
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Definition
| four to eight of these make up muscle spindles & are surrounded by a capsule of connective tissue |
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Definition
| true force-producing fibers; in skeletal muscle; run in a parallel arrangement with intrafusul muscle fibers & contain some as well |
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Definition
| secondary endings; produce sustained responses to constant muscle lengths; opposite of group Ia afferents |
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Definition
| low-threshold mechanoreceptors in tendons that inform the central nervous system about changes in muscle tension |
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Definition
| branches of these make up Golgi tendon organs and are distributed among the collagen fibers that form the tendons |
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Definition
| resemble many of the receptors found in the skin; mechanoreceptors in and around the joints |
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Term
| dorsal columns (AKA posterior funiculi) |
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Definition
| where the axons of cutaneous mechanosensory afferents ascend through the spinal cord; leads the axons to the lower medulla where they synapse on neurons in the dorsal column nuclei |
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Definition
| a circumscribed bundle in which fibers conveying information from lower limbs travel |
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Definition
| a lateral bundle in which fibers that convey information from the upper limbs, trunk, & neck lie |
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Term
| The _____ in the dorsal column nuclei send their axons to the somatic sensory portion of the thalamus |
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Definition
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Term
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Definition
| the axons exiting from the dorsal column nuclei |
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Definition
| a dorsoventrally elongated tract formed by the internal arcuate fibers that cross the midline |
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Term
| the crossing of the internal arcuate fibers is called the _____ of the medial lemniscus |
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Definition
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Term
| ventral posterior lateral nucleus/VPL |
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Definition
| where the axons of the medial lemniscus synapse with thalamic neurons |
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Term
| _____ in the VPL send their axons via the internal capsule to terminate in the postcentral gyrus of the cerebral cortex, a region known as the primary somatosensory cortex (AKA SI) |
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Definition
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Term
| secondary somatosensory cortex/SII |
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Definition
| a smaller region than the primary somatosensory cortex that lies in the upper bank of the lateral sulcus; another place where neurons in the VPL send their axons |
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Term
| trigeminal ganglion/cranial nerve V ganglion |
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Definition
| where first-order neurons are located that centrally convey cutaneous mechanoreceptor information from the face |
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Term
| what are the three main subdivisions of the trigeminal nerve? (formed by the peripheral processes of the trigeminal ganglion) |
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Definition
1. ophthalmic
2. maxillary
3. mandibular |
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Term
| trigeminal brainstem complex |
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Definition
| where the trigeminal ganglion cells terminate on neurons after entering the brainstem at the level of the pons |
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Term
| 2 major components of the trigeminal complex |
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Definition
1. principal nucleus
2. spinal nucleus |
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Term
| ventral posterior medial nucleus/VPM nucleus |
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Definition
| where axons of the second-order neurons of the trigeminal brainstem nuclei ascend to after crossing the midline |
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Term
| trigeminothalamic tract (AKA trigeminal lemniscus) |
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Definition
| how the second-order neurons of the trigeminal brainstem complex send their axons to the VPM nucleus |
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Term
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Definition
| located in the medial aspect of the dorsal horn; where first-order proprioceptive afferents that enter the spinal cord between the mid-lumbar & thoracic levels synapse |
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Term
| mesencephalic trigeminal nucleus |
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Definition
| a well-defined cluster of neurons lying at the lateral extent of the central gray region of the midbrain; where the cell bodies of the first-order proprioceptive neurons for the face are found; in the central nervous system |
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Term
| ventral posterior complex |
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Definition
| part of the thalamus; where each of the several ascending somatic sensory pathways originating in the spinal cord & brainstem converge |
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Term
| primary somatic sensory cortex (AKA SI) |
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Definition
| located in the postcentral gyrus of the parietal lobe; comprises 4 distinct regions/fields |
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Term
| 4 distinct regions/fields of the primary somatic sensory cortex |
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Definition
1. Brodmann's area 3a
2. Brodmann's area 3b
3. Brodmann's area 1
4. Brodmann's area 2 |
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Term
| secondary somatosensory cortex/SII |
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Definition
| lies in the upper bank of the lateral sulcus; one of the higher order cortical centers to which somatic sensory information is distributed from the primary somatic sensory cortex |
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