Somatic sensation and ascending pathways Flashcards
What is a sensory modality? Give general somatic sensory examples
How a stimulus is perceived temperature pain pressure/crude touch vibration fine touch proprioception 2 point discrimination
What determines the sensory modality
The type of receptor
What modality is wetness?
It is a combination of modalities (e.g. temp and fine touch)
Briefly describe the route of a primary sensory neurone
Cell body is found in the dorsal route ganglion
Crosses from PNS to CNS
Briefly describe the route of a secondary sensory neurone
Cell body is found in the spinal cord (sometimes brainstem) Crosses midline (decussates)
Briefly describe the route of a tertiary sensory neurone
Cell body is found in the thalamus
Projects to the primary sensory cortex
Briefly describe the types of primary neurones
Rapidly adapting- signal degenerates over time
e.g. mechanoreceptors in the skin
Slow adapting- signal frequency doesn’t decay
e.g. nociceptors (pain transmission)
What is a receptive field
The area of skin that a sensory neurone collects information from
What is the relationship between acuity and the receptive field?
Inversely proportional
Smaller receptive field= greater acuity
What is the clinical significance of receptive fields overlapping?
Determine dermatomal sensation in the middle of the dermatome, where it is less likely there will be any overlap
Briefly describe two benefits of the orderly and parallel way in which the corresponding CNS is organised
Requires minimum amount of ‘building material’ e.g. axons, myelin, neurones
Converts information from dermatomes into the homunculus
What system is the modality of pain relayed to the cortex by?
Spinothalamic (anterolateral) system
What system is the modality of crude touch relayed to the cortex by?
Spinothalamic (anterolateral) system
What system is the modality of temperature relayed to the cortex by?
Spinothalamic (anterolateral) system
What system is the modality of fine touch relayed to the cortex by?
Dorsal column system
