NBSS: (Neuroscience) Somatosensory Systems Flashcards
what are the 4 Physiological mechanisms of sensation
- TRANSDUCTION - transduce energy of the sensation into an electrical response which is done peripherally by the receptors
- TRANSMISSION - this gets transmitted down the axon of the first order sensory neurones that are largely the neurones of in the DRG except the head which is innervated by the trigeminal ganglion.
- PERCEPTION - goes to the brain to the thalamus and then the somatosensory cortex.
- MODULATION - the brain will send signals to modulate the amount of input it receives.
Touch is mediated by 4 types of mechanoreceptors, what are the names
What do proprioreceptors report on?
Limb position and movement
What are the joint receptors?
Sensory receptors in the joint
Joint capsule receptors transduce tension in the joint capsule while perception of angle achieved via afferent signals from muscle spindles and efferent motor commands.
how do muscle spindles lie with main muscle fibres
Muscle spindles lie in parallel with main muscle fibres
how do golgi tendon organs lie with muscle fibres?
Golgi Tendon Organs lie in series with main muscle fibres and are sensitive to changes in muscle tension
What do the primary sensory neurons form?
- DRG are in the periphery.
- Primary sensory neurons form two principal subgroups, A large and C small.
most cold-sensitive fibres in humans are …
small myelinated Aδ axons
15-30 degrees
most warm-sensitive fibres in humans are
small unmyelinated C axons
30-45 degrees
What are the 4 main modalities of nociceptors?
What 4 properties of a stimulus do receptors respond to?
- Modality: different receptors are activated by different type of stimuli (‘adequate stimulus’); the concept of receptor specificity; depends on the presence of different transduction molecules
- Intensity: encoded by firing frequency (and number of receptors activated; also different receptors have different thresholds of activation: receptor sensitivity)
-Duration: encoded by duration of firing (and changes in spike trains)
-Location: related to receptive fields
How is information on intensity and duration of stimuli is conveyed?
Information on intensity and duration of stimuli is conveyed by changes in the firing rates of sensory neurons.
What is the receptive field?
The receptive field of a sensory neuron is the spatial domain where stimulation excites (or inhibits) the neuron.
how is the receptive field arranged?
in a somatotopical way: neurones with receptive fields are close to eachother and connect to parts of the spinal cord which are also close
What is a dermatome?
A dermatome is the area of skin and deeper tissues innervated by a single dorsal root ganglion
Describe the dorsal columns/medial lemniscal system.
(red) ascends ipsilaterally in the spinal cord, and conveys mechanosensory information from the limbs and trunk to the cortex via to the VPL thalamus.
Describe the contralateral anterolateral system.
(in brown; spinoreticular, spinomesencephalic and spinothalamic tracts) crosses the midline in the spinal cord and transmits itch, temperature, and visceral information to the cortex via the brain stem and thalamus.
