3 - Somatosensory system 2 Flashcards
Which arteries supply the dorsal column?
Posterior spinal arteries (x2)
Which artery supplies the majority of the spinal cord (except dorsal column) ?
Anterior spinal artery
What are the 2 main ascending sensory tracts of the somatosensory system?
1) Dorsal Column Medial Lemniscus pathway (DCML)
2) Spinothalamic pathway
Which somatic senses are transported via the DCML pathway?
- Light touch
- Vibration
- Proprioception
- 2-point discrimination
Which somatic senses are transported via the spinothalamic pathway?
- Pain
- Crude touch
- Temperature
Describe the path of the 1st order neurones of the DCML pathway:
From origin to medulla
up spinal cord ipsilateral to the side of origin
Describe the path of the 2nd order neurones of the DCML pathway:
From medulla to thalamus
Decussate at medulla
Describe the path of the 3rd order neurones of the DCML pathway:
From thalamus to post-central gyrus
via internal capsule
Where do the neurones of the DCML pathway decussate?
Medulla
If a 1st order neurone entered the DCML pathway from the hand, where would it lie in the spinal cord compared to a neurone from the foot?
More laterally
Cervical neurones lie most laterally, sacral lie most medially
Describe the path of the 1st order neurones of the spinothalamic pathway:
From origin, enters spinal cord and synapses a few levels above
Describe the path of the 2nd order neurones of the spinothalamic pathway:
From distal spinal cord, decussates immediately, ascends CONTRALATERAL to site of origin, to thalamus
Describe the path of the 3rd order neurones of the spinothalamic pathway:
From thalamus to post-central gyrus
via internal capsule
If a 1st order neurone entered the spinothalamic pathway from the hand, where would it lie in the spinal cord compared to a neurone from the foot?
More medially
Cervical neurones lie most medially, sacral lie most laterally
Which fibres carry pain?
C fibres
Which fibres carry mechanoreceptor impulses?
A fibres
If you bang your knee, why does rubbing it make it less painful?
Descending control of pain: Rubbing = activation of mechanoreceptors = activated A fibres = excite inhibitory enkephalinergic interneurones in spinal cord = bind to u-opioid receptor = inhibit spinothalamic tract
Name some causes of insensitivity to pain:
- Congenital insensitivity to pain
- Trauma
- Diabetes
- Chronic kidney disease
- Chronic liver disease
- Excessive alcohol intake
- Cancers
- Hypothyroidism
- Acromegaly
- Guillian-Barre syndrome
- Inf: Shingles, HIV, Lyme disease
- AI: RA, SLE
- Drugs: Chemotherapy, HIV tx
