Somatosensory system 1 Flashcards
What is the somatosensory system?
The system that mediates all the senses except for special senses (vision, taste, smell, hearing, balance)
Which senses are included in the somatosensory system?
Mechanosensation Proprioception Thermosensation Nociception Pruriception
What do low threshold mechanoreceptors and thermoreceptors mediate?
Touch, vibration, pressure
Cold, cool, indiffferent, warm, hot
What do high threshold mechanoreceptors, thermal nociceptors, chemical nociceptors and polymodal nociceptors mediate?
- High intensity mechanical stimulation
- Extreme degrees of heat
- Substances in tissue eg inflammatory mediators
- At least 2 of the above
Describe a slow acting response in sensory neurones
Continuous infromtaion to CNS while terminal deformed. Provides information about position, degree of stretch and force eg stretch receptor
Describe rapid acting response in sensory neurones
Detects changes in stimulus strength (eg rate of movement)
Number of impulses proportional to rate of change of stimulus
e.g some muscle spindle afferents, hair follicle afferents
Describe very rapidly acting response in sensory neurones
Responds only to very fast movement e.g rapid vibration
As a general rule, what are the functions of the dorsal and ventral roots of spinal nerves?
Dorsal- Sensory
Ventral- Motor
Define the term dermatome
An area of skin innervated by the left and right dorsal roots of a single segment
Why does the anterior head not have a dermatomal distribution?
This area is supplied by the trigeminal system
Why are the C4, 6 7 and 8, T4, 6 and 10, L4, 5 and S1 roots clinically relevant?
If one of these dorsal roots is cut, some sensation will be maintained due to overlap between adjacent dorsal roots.
What happens to the ration of white to grey matter in the spinal cord moving from sacral to cervical, and why?
It increases as more and more fibre tracts are added from different body parts to the spinal cord moving superiorly
