Lecture 4-Sensory System Flashcards
What are modalities?
Unit of sensation, due to different types of receptors
What are the modalities associated with the dorsal column pathway?
- fine touch
- 2 point discrimination
- vibration
- proprioception
What are the modalities associated with the spinothalamic tract?
- temp
- pain
- pressure/crude touch
- stretch
Where is the dorsal column pathway found?
In the dorsal funiculus
Where is the spinothalamic system found?
On the cap on the surface of the ventral horn
True or false: a strong receptor activation leads to an increased frequency AP
TRUE
What are rapidly adapting units?
Good at detecting changes in AP eg rapidly adapting mechanoreceptors in skin
What are slowly adapting units?
Frequency of AP stays the same eg nociceptors/pain
What is a receptive field?
Region of sensory space in which a stimulus will modify the firing of that neuron (multiple receptors feed into sensory neurone)
What is acuity inversely proportional to?
Size of receptive field
Where is the cell body of the primary sensory neurone?
Dorsal root ganglion (DRG)
Where is the cell body of secondary sensory neurone?
Dorsal horn/medulla
Where is the cell body of tertiary sensory neurone?
Thalamus
Where does the tertiary sensory neurone project to?
Primary sensory cortex in post-central gyrus
True or false: primary sensory neurone decussates
FALSE - secondary decussates
In the dorsal column pathway, where does the lower body map to?
Medial portion of tract
In the spinothalamic tract, where does the lower body map to?
Lateral parts of tract
What is the cuneate nucleus in the dorsal column pathway responsible for?
Upper 1/2 of body
What is the gracile nucleus in the dorsal column pathway responsible for?
Lower 1/2 of body
What is the name of the pathway in the dorsal column pathway in which the secondary neurones travel?
Medial lemniscus pathway
Where does the secondary neurone decussate in the spinothalamic tract?
White ventral commissure
In a complete cord hemisection in which a single cord segment is destroyed, which structures are destroyed unilaterally?
- dorsal horn
- ventral horn
- all other cord grey matter
- all white matter pathways
- dorsal and ventral roots
What are the signs of Brown-Sequard syndrome?
- ipsilateral complete segmental anaesthesia affecting single dermatome
- ipsilateral loss of dorsal column modalities below the lesion
- contralateral loss of spinothalamic modalities below the lesion
Which fibres carry impulses from mechanoreceptors in damaged skin?
A fibres
