Somatosensory Pathways Flashcards
what is the name of the nucleui where fasciculus gracilis and fasciculus cuneatu project onto? [2]
what is the collective name for these nuclei? [1]
at which location? [1]
what is the name of the nucleui where fasciculus gracilis and fasciculus cuneatu project onto? [2]
fasciculus cuneatu –> cuneate nuclei
fasciculus gracilis –> gracile nuclei
what is the collective name for these nuclei? [1]
dorsal column nuclei
at which location? [1]
lower medulla
* what is special about the fibres in dorsal column? [2] *
not arising from relay cells in dorsal horn. instead are connect directly to peripheral nerve.
ascend cord on same side as where they come in dorsal root
the first synapse in the discrimative touch pathway is where?[1]
describe the pathway of this tract after this xo [5]
the first synapse in the discrimative touch pathway is where?[1]
dorsal column nuclei
where does axon go after this ^?
- *- dessucate to the medial lemniscus via internal arcuate lines
- medial lemniscus contains second order fibres
- travel up to the somatosensory thalamus in brain (together, often call dorsal column-medial lemniscal)**
describe pathway of cutaneous afferents from the face? [1]
- Cutaneous afferents from the face travel in cranial nerves and enter the trigeminal nucleus
- Post-synaptic fibres from the trigeminal nucleus decussate and run alongside the medial lemniscal fibres from the body.
- the face afferents end in the VPM thalamus (ventro-postero-medial nucleus),
where do you find the cell bodies of the trigeminal nerve? [1]
what do all inputs to the somatosensory cortex come via? [1]
The cell bodes of the trigeminal nerve are in the trigeminal ganglion,
thalamus
afferents from the face end come up through the medial lemniscus and terminate in which part of the thalamus? [1]
afferents from the body come up through the medial lemniscus and terminate in which part of the thalamus? [1] [1]
afferents from the face end come up through the medial lemniscus and terminate in which part of the thalamus? [1]
VPM- ventro-postero-medial
afferents from the body come up through the medial lemniscus and terminate in which part of the thalamus? [1]
ventero-postero-lateral: VPL
(together they form complete somatosensory thalamus)
what is corticol selective input?
*** what are the VPM and VPL? [2] ***
VPL = Ventral Posterolateral Nucleus. primary thalamic relays for somatic sensation; that is, nociceptive and tactile/proprioceptive information from the body
VPM = ventral posterolateral nucleus. primary thalamic relays for somatic sensation; that is, nociceptive and tactile/proprioceptive information from the head
both nuclei in the thalamus !!
regarding primary somatosensory and motor cortexes, which areas of the body have the highest density of touch receptors? [3]
hands, lips and tongue: areas with highest density of touch receptors occupy the largest areas of the cortical map
what is romberg’s test? what are you testing? how do you perform? what is a postive sign? [1]
Romberg’s test:
- tests proprioception
- standing patient and close eyes. instability & loss of balance is a positive sign
- called sensory ataxia (due to dorsal column damage)
what type of ending do nocipeptors have? [1]
what myelination does fast pain have? [1]
what myelination does slow pain have? [1]
what type of ending do nocipeptors have? [1]
free nerve endings
what myelination does fast pain have? [1]
αδ
what myelination does slow pain have? [1]
C
why are nociceptors described as polymodal? [3]
nociceptors tend to respond to thermal, mechanical, and chemical stimuli,
why does inflammation produce long lasting pain?
tissue damage releases pro-inflam chemicals into extracellular space
these chemicals (e.g. bradykinin, K+) activate nociceptor & cause it to stay open for long depolariastion
explain path of lateralspinothalamic tract
lateral spinothalamic tract:
decussates at site of entry and goes up
- axons reach midbrain, they branch to different nuclei
i) periaqueductal grey (PAG) - arousal
ii) mediodorsal nucleus
iii) ventromedial thalamic group
ii & iii = where concious perpection of pain is registered !
BUT NOT TO VPL / VPM (i.e. not somatosensory
where do you find the insula? [1]
between which lobes? [2]
where do you find the insula? [1]
lateral fissure
between which lobes? [2]
frontal and temporal
** what changes would be felt bc of this lesion (brown-sequard)? **
- loss of pain and temperature on right side of body below lesion (spinothalamic decussates at level of spinal cord entry)
- loss of motor movement on same side as lesion (corticospinal goes down ipsilateral side)
- loss of proprioception and vibration sense on the same side from damage (DCML has already decussated)
