4. The Somatosensory System Flashcards
What is the somatosensory system for?
Conscious sensation, and skin and muscle innervation
What are the different sensory modalities?
Temperature Pain Vibration Stretch 2 point discrimination Proprioception
Why are the different sensory modalities clinically relevant?
They exist as different types of receptor
Aside from which modality is used, what else is clinically relevant?
The quality of modality as the receptor subtypes fire at different levels
What is the generic rule for the chain of 3 neurones in the somatosensory system?
- afferent first order sensory neurone body found in dorsal root ganglion
- 2nd order neurone crosses the midline
- tertiary neurone projects from the thalamus to the sensory cortex
How does the primary neurone encode information?
Ion fluxes from receptor cause generator potentials which fire if thy reach threshold
What is the amount of stimulus at the receptor proportional to?
The number of action potentials fired
What are the 2 types of somatosensory receptors?
Phasic receptors and tonic receptors
Tell me about phasic receptors.
Rapidly adapting receptors
Adapt to continuing pressure like clothing on skin
E.g. mechanoreceptors
Tell me about tonic receptors.
If the stimulus remains, the AP remains - no adaptation so dont get used to pain.
E.g. nociceptors
What is the receptive field?
The area of skin covered by 1 given sensory neurone.
