The cutaneous senses Flashcards
What four problems are caused by losing the sense of touch?
Prone to injuries
Difficulty interacting with the environment
Difficulty moving
Difficulty with sexual activity
What three functions characterize the somatosensory system?
Cutaneous senses - responsible for touch and pain
Proprioception - ability to sense the positions of the body and limbs
Kinesthesis - ability to sense the movement of the body and limbs
Identify the two layers of the skin
Epidermis - outer layer of dead skin cells
Dermis - inner layer containing mechanoreceptors
Identify the four mechanoreceptors by function and type
Merkel receptor (SA1) - slowly adapting fibres; fine detail, shape, texture Meissner corpuscle (RA1) - rapid adapting fibres; controlling handgrip, preceiving motion across skin Ruffini cylinder (SA2) - slowly adapting fibres; perceiving stretching of skin Pacinian corpuscle (RA2) - rapid adapting fibres; sensing rapid vibrations and fine texture
Which two receptors are located closer to surface of skin? Which two receptors are located deeper in the dermis?
Shallow - Merkel and Meissner
Deeper - Ruffini and Pacinian
Identify and describe the two nerve fibre pathways
Medial lemniscal pathway - large fibres carrying signals related to proprioception and perceiving touch
Spinothalamic pathway - smaller fibres carrying signals related to pain and temperature
Describe the pathway of cutaneous neurons
Mechanoreceptors –> spinal chord/dorsal root –> ventrolateral nucleus in thalamus –> somatosensory receiving area (S1) and secondary somatosensory cortex (S2) in parietal lobe
Homunculus
Body map of somatosensory cortex depicting locations of sensory areas for different body parts
Which body parts take up a disproportionately large area of the homunculus?
Fingers (necessary to detect details in touch)
Give an example of how experience-dependent plasticity is observed in humans
Violin players having greater than normal cortical representation for fingers of left hand
Two-point threshold
Experimental technique to detect the minimum detectable separation of two objects applied to skin
Grating acuity
Experimental technique to indicate the narrowest detectable grating spacing of object applied to skin
Which receptor types are used to detect fine texture and detail
Merkel receptor (SA1) Pacinian corpuscle (RA2)
Surface texture
The visual and tactile quality of a surface created by peaks and valleys
Duplex theory of perception
Perception of texture depends on both spatial cues and temporal cues
Spatial cues
Relatively large surface elements, such as bumps and grooves, that can be felt both when the skin moves across the surface elements and when it is pressed onto the elements
Temporal cues
Smaller surface elements felt by moving the skin across surface; responsible for perception of fine texture
Active touch
Person actively exploring an object
Passive touch
Touch by which an object is pressed into stationary skin
Haptic perception
Perception by which three-dimentional objects are explored with the fingers and hand
Exploratory procedure
Identifying an object by movements of hands and fingers on object
What are the four exploratory procedures?
Lateral motion
Contour following
Enclosure
Pressure
Somatosensory cortical responding is affected by which three factors?
Neuron specialization
Conscious attention
Visual attention
Where are centre-surround cortical neurons located?
Ventral posterior nucleus and somatosensory cortex
Neurons in the somatosensory cortex can take on which two specialties?
Centre-surround orientation
Specialized movements/orientations
What are the three types of pain?
Inflammatory
Neuropathic
Nociceptive
Pain matrix
Subcortical: thamalmus, hypothalamus, limbic system
Cortical: Insula, anterior cingulate, prefrontal cortex
