The Sensory System Flashcards
What are the 7 modalities of sensation?
Which pathways are responsible for these?
Temperature
Pain
Pressure/Crude touch
SPINOTHALAMIC TRACT
Vibration Proprioception Fine touch 2-point discrimination DORSAL COLUMN
The dorsal column is responsible for which sensory modalities?
2- Point discrimination
Fine touch
Vibration
Proprioception
Remember: “2 Fingers PV”
The spinothalamic system is responsible for which sensory modalities?
Pain
Pressure
Temperature
Remember: “Ppt.”
Give an example of rapidly adapting receptors and explain why they are necessary.
Mechanoreceptors
Useful when we don’t want to sense something all of the time, e.g. chair you are sitting on, feel it initially and then the AP frequency dies down
Give an example of slowly adapting receptors and explain why they are necessary.
Nociceptors
When sensing pain, you don’t want the body to get used to the pain stimulus
APs fire until the stimulus is removed
Acuity is indirectly proportional to what?
How does this translate for big regions of skin and small regions of skin in relation to their acuity?
The size of the receptive field
Where do primary neurones have their cell body?
In the dorsal root ganglion
Primary neurones receive information from where?
From the receptor
Does the axon remain ipsilateral or travel contralateral to the cell body in primary neurones?
Remains ipsilateral
Where is the cell body of secondary neurones found?
In the dorsal horn or the medulla
What is the key feature of the secondary neurone?
It decussates
Where does the cell body of the tertiary neurone lie?
In the thalamus
Where does the tertiary neurone project to?
Primary sensory cortex
Post-central gyrus
In the dorsal column pathway, the lower body maps to the ______ portion of the tract.
Medial
In the spinothalamic tracer, the lower body maps to the ______/______ parts of the tract.
Lateral/superficial
Isolated lesions of the dorsal column pathway in the cord lead to signs that are contralateral or ipsilateral?
Ipsilateral
Isolated lesions of the spinothalamic tract in the cord lead to signs which are contra- or ipsilateral?
Contralateral
A complete cord hemisection causing destruction of a single cord segment will result in which structures being destroyed unilaterally?
- The dorsal horn
- The ventral horn
- All other cord grey matter
- All white matter pathways
- Dorsal and ventral roots
Complete cord hemisection causing destruction of a single cord segment by traumatic or vascular injury will lead to which signs?
Ipsilateral complete anaesthesia of a single dermatome (due to loss of dorsal horn and dorsal root)
Ipsilateral loss of dorsal column modalities below the lesion (not yet decussated)
Contralateral loss of spinothalamic modalities below the lesion (decussated already)
What is the name given to the syndrome that emerges when one half of the spinal cord is destroyed?
Brown-Sequard syndrome
What is the role of A fibres in the control of pain?
How could you activate these fibres following an injury?
A fibres carry impulses from mechanoreceptors in the skin to alleviate pain
Rub the area of skin
Apply heat
How do A fibres carry out their function of pain alleviation?
Excite inhibitory enkephalinergic (EnK) INTERNEURONES in the cord
Which fibres are responsible for carrying pain?
C fibres (primary afferents)
