37 terms

Somatosensory System

Chapter 7 Test Preparation
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Primary Sensory Cortex
Input mainly from thalamic relay nuclei.
Secondary Sensory Cortex
Input mainly from the primary and secondary cortex of the same region.
Association Sensory Cortex
Input from several sensory systems, usually from secondary cortex systems.
Hierarchical Organization
Specificity and complexity increase with each level of perception.
Sensation
Detecting the stimulus.
Perception
Understanding the stimulus.
Functional Segregation
Distinct functional areas within the hierarchy.
Parallel Processing
Simultaneous analysis of signals along different pathways.
Former Model
Hierarchical, Functionally Homogenous, Serial
Functionally Homogenous
Similar processing across a single level of the hierarchy.
Serial Processing
Signal is processed in a ascending order from receptor to association cortex.
Current Model
Hierarchical, Functional Segregation and Parallel Processing
Somatosensory System
Three components, exteroceptive, proprioceptive, and interoceptive.
Exteroceptive
Stimuli from outside the body, i.e. touching the body.
Proprioceptive
Position of the body, input from muscle tension and tendon strain.
Interoceptive
Internal body conditions, i.e. temperature and blood pressure.
Exteroceptive System
3 components, touch (mechanical stimuli), temperature (thermal stimuli), pain (nociceptive stimuli). Specialized receptors to each stimuli.
Cutaneous Receptors (Touch)
Four receptors distinguished by receptive field size and speed of response. Can detect slow surface movement or pressure and fast vibrations.
Free Nerve Ending
Part of the cutaneous system, this receptor detects temperature and pain.
Messner Corpuscles
Part of the cutaneous system these are encapsulated, found in dermis, receptors for discriminative (light touch).
Pacinian Corpuscles
Part of the cutaneous system these are large, round and onion like receptors that respond to deep pressure and vibration.
Merkel's Discs
Cutaneous system: detect gradual skin indentation.
Ruffini Endings
Cutaneous receptor: detects gradual skin stretching.
Stereognosis
The identification of objects by touch.
Dynamic and Static Qualities
This differentiation allows for full appreciation of objects in out physical world, as well as helps us understand that cutaneous receptors respond more to change than to constant contact.
Dermatome
An area of the body that is innervated by the left AND right dorsal roots of a given segment of the spinal cord.
2 Major Paths of Signal Transfer
The dorsal-column medial-lemniscus system and the anterolateral system.
Dorsal-column medial-lemniscus System
Fine discriminitive touch, proprioception, vibration, carries information to contralateral post central gyrus, crosses in the medulla. Decussates to contralateral hemisphere.
Anterolateral System
Tends to carry information about pain and temperature. Synapse upon entering the spinal cord.
Somatosensory Agnosias
Conditions that occur from damage to the sensory cortex.
Asomatognosia
Failure to recognize part of one's own body.
Anosognia
Failure to recognize one's own symptoms.
Contralateral Neglect
Tendency to ignore one half of one's environment.
Pain
Has no cortical representation, however the anterior cingulate gyrus does seem to be connected to the emotional components of pain.
Descending Pain Control
Allows for the suppression of pain.
Anterior Cingulate Cortex
Mediates the emotional component of pain.
Orbital Frontal Cortex
The cognitive evaluation of pain and emotion.
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