Lec 10 Flashcards
The anterolateral pathway consists of what three ascending pathways
- spino-thalamic tract
- spino-reticular tract
- spino-mesencephalic tract
Describe the path that the antero-lateral pathway takes
(Need to review what I must know
- Primary sensory neuron synapse to second order nuclei in dorsal horn
- Immediately decussate over 2-3 spinal segments then ascends in antero-lateral pathway.
- travels through rostral medulla
- (need know??) once gets to pons, bifurcates into spinoreticular tract, the rest goes up to midbrain and splits into spinomesencephalic (which bifercates again after that) and the main Spinorthalamic continues before splitting again into the one that goes to the third order neuron (then goes to cortex) and the branch that goes to the intralaminar and mediol-dorsal nuclei.
Describe the path that the antero-lateral pathway takes
Based off lecture notes**
- Primary sensory neuron synapse to second order nuclei in dorsal horn
- Immediately decussate over 2-3 spinal segments through anterior commissure then ascends in antero-lateral white matter/pathway.
- Passes through rostral medulla, then pons, then midbrain, then second order neurons synapse to third order neurons in thalamus (ventral posterior lateral nucleus of thalamus)
- Third order neurons project to somatosensory cortex
What is the somatotopic organization in the anterolateral pathway
Legs are lateral
Arms are medial
What does the thalamus do for the purposes of this course
relay information to other brain regions
where is the somatosensory cortex in relation to the central sulcus and the primary motor cortex
just behind the central sulcus, just in front of that is the primary motor cortex.
Order = primary motor, sulcus, somatic
describe the homunculus for the motor cortex vs somatosensory cortex. Highlight differences between them
motor:
middle fold is toes, leg, knee,
then after cortex go laterally is hip, trunk, arm, elbow, hand fingers,
About half way down, neck, face, then tongue larynx and pharynx at bottom
Somatosensory:
same except first thing in fold is genitals,
head and neck come before arms (back of head where there is sensory info but no muscles to move)
rest is about the same
What are the negative symptoms of somatosensory lesions in PCML pathway
Loss of:
- vibration and position sense
- discriminatory touch (2 point discrimination)
- astereognosis (cant recognize ob by touch)
what do you call the inability to recognize objects by touch
astereognosis
what is sensory ataxia
Term for disorder that cause loss of coordinated movement, unsteady gait and balance etc.
Dog proprioception
describe traits of tabetic (ataxic) gait
where injury happen to cause this?
high stepping
foot flapping
unsteady (without vision)
sensory inj regarding lower limbs
Posterior column below T6?
what is the primary sensory neuron
how can you tell if there is damage here (symptom)?
the neuron that directly receive info from the environment (comes before second order)
can tell is damaged if you have loss of stretch reflex, if damaged above, still have stretch reflex (mono ref arc)
what are the negative symptoms of somatosensory lesions in the spino-thalamic pathway?
how can you test this?
- loss of pain and temp sense
- reduced touch sensation
can test by running tooth pick along skin (will feel the sharpness but won’t be “painful” to the patient)
test putting objects of different temperatures on patient
difference between positive and negative symptoms of somatosensory lesions
negative means loss of, pos means heightened sense
what are the positive symptoms of lesions to the PCML path, antero-lateral path, and primary sensory neurons?
PCML - tingling, numb sensation
Antero-lateral path - sharp, burning, searing pain
Primary sensory neurons (nuclei/nerve root) - radicular pain (sharp, shooting, burning, tingling, or numb sensation that radiates through dermatome).
what is radicular pain?
sharp, shooting, burning, tingling, or numb sensation that radiates down nerve
parasthesia (dysesthesia), what pathway does it involve
abnormal sensations (but not painful) e.g. tingling, pins and needles
involves PCML path
what do hyperpathia and allodynia have in common
what pathway involve?
both are a pain response to a non-painful stimulus.
anterolateral pathway
what nerve innervates the face sensory info, what else does it innervate (1)
trigeminal nerve (CN V)
also innervates muscles fro mastication
where do sensory inputs from the face first join?
trigeminal ganglion in Merkel’s cave
What three trigeminal sensory systems must I know
what each do, and what path each take?
Mesencephalic trigeminal nucleus - proprioception
Chief trigeminal sensory nucleus - fine touch, dental pressure
- trigeminal lemniscus
spinal trigeminal nucleus - crude touch, pain, temp
- trigeminothalamic tract
complete the sentence. “Primary sensory neurons synapse on second-order sensory nuclei on ______ side. Second order neurons ________ and travel to the ______. Third order neurons from the _____ to the ______.
ipsilateral side
cross sides/decussate
thalamus
thalamus
somatosensory cortex
Difference between sensory cortex and somatosensory cortex
sens cort - broad term for all sensory info
somato - areas involved in processing touch, proprioception, pain, and temperature, located in the parietal lobe.
for the facial somatosensory nerves, damage to what areas would cause ipsilateral damage?
contralateral?
anything below the thalamus and before decussation would cause ipsilateral,
anything after decussation cause contralateral effects. (thalamus, somatosensory cortex)
Includes:
- trigeminal lemniscus (fine touch, vibration, and proprioception from the face).
- trigeminal thalamic tract (pain and temperature but includes bilateral projections from the spinal trigeminal nucleus).
