L13: Somatosensory system Flashcards
Somatosensory receptors/neurons can encode what four main features of a stimulus?
MILD
- modality
- intensity
- location
- duration
What are the 3 types of somatosensory receptors in the skin? What do they detect?
- Mechanoreceptors – touch, pressure
- Thermoreceptors - temperature
- Nociceptors – noxious stimuli (triggering pain sensation)
What are the 5 types of mechanoreceptors in the skin?
- Meissner’s corpuscles
- Pacinian corpuscles
- Merkel’s discs
- Ruffini endings
- Hair units
What stimuli do Meissner’s corpuscles detect?
Glabrous skin (mostly), pressure, dynamic, rapidly adapting, low threshold
What stimuli do Pacinian corpuscles detect?
Subcutaneous (all skin), interosseous, viscera, deep pressure, vibration, dynamic, rapidly adapting, low threshold
What stimuli do Merkel’s discs detect?
All skin, static pressure, convey info about shape & texture of objects, slowly adapting, low threshold
What stimuli do Ruffini endings detect?
All skin, deeper pressure & stretch, slow adapting, low threshold
What stimuli do Hair units detect?
Hairy skin, hair displacement, low threshold, rapidly adapting
Describe what rapidly adapting means
only detecting the change in the sensory stimulus, at the onset of stimuli, firing stops after this = rapidly adapting signals
Describe what slowly adapting means
APs fire whole time stimulus is present, tells us about the duration of the stimuli
Compare and contrast thermoreceptors to nociceptors in the skin
Both free nerve endings, in all skin
- Myelinated axons = Temperature (usually change in temp rather than absolute temp)
- Nociceptors (respond to mechanical, thermal, or chemical stimuli) = activated by intense stimuli → have high threshold
What are proprioceptors? What info do they encode?
- Mechanoreceptors in muscles and tendons
- Provide information relating to change in muscle length & force
What is an example of a proprioceptor? What does it do? Where is it found?
Golgi tendon organ
* for muscle force
* found where muscle meets tendon
* Used by CNS to sense limb
movement & limb/body position
What are enteroceptors?
Sensory receptors and afferent nerves associated with internal organs, usually associated with ANS function
Describe the structure and location of sensory afferent neurons (e.g. cell body, processes, axons, dendrites etc.)
- unipolar neuron
- Cell body typically located in dorsal root ganglia, or cranial nerve ganglia
- Central process enters CNS
- the area the dendrites cover defines receptor field
- Nerve endings may be free or encapsulated
