Lecture 10 Flashcards
Anterolateral pathway consists of which ascending pathways
-spino-thalamic tract: from spinal cord to thalamus
- spino-reticular tract- from spinal cord to regions of reticular formation
- Spino-mesencephalic tract: innervates at level of the midbrain
- All come from same receptor and branch off to go to different areas, below midbrain all the same tracts
Describe the anteriolateral pathways
Nerve endings send axons though dorsal root to cell bodies in ganglion. Primary sensory neuron synapses with second order sensory nuclei in dorsal horn (on ipsilateral side) of cell bodies. Second order sensory neuron crosses the midline through anterior commisure (over 2-3 segments) to ascend in antero-lateral white mater. Second order neuron synapses onto third order sensory neurons in thalamus. Third order sensory neurons project to somatosensory cortex.
Identify this pathway
anterolateral pathway
Identify this pathway
anterolateral pathway
Identify this body part
neck
Identify this body part
arm
Identify this body part
trunk
Identify this body part
leg
Describe somatotopic organisation of antero-lateral pathway
leg (distal regions)= lateral
arms= medial
As go up the body sgements layer in medially
Describe the thalamus
-major relay centre for sensory information and cortical inputs
-primary area of integration of sensory information, cerebellar and basal ganglia inputs
- collection of relay nuclei- can modulate information and outputs in out cortex for further processing
Identify this
thalamocortical and corticothalamic projections
Identify this
basal ganglia
Identify this
limbic system
Identify this
reticular formation
Identify this
cerebellum
Identify this
somatosensory, auditory, visual, vestibular and other inputs
Primary sensory cortex makes up _______
post central gyrus
Identify this
somatosensory homunculus
Identify this
motor homunculus
Describe the organsiation of the primary somatosensory cortex
feet in midline, lower leg knee superior, leg, trunk, back of head, arm, had, face most lateral, tongue (visural sensation). Largest represenation of hand and face
“negative” symptoms
subtraction/removal od normal sensation
Negative symtoms of somatosensory lesions- PC-ML pathway
-loss of position (proprioception) and vibration sense
-loss of discriminatory touch (2 point descrimination)- light touch
-astereognosis (stereoagnosia)- inability to recognise objects by touch
-sensory “ataxia”- unsteady balance and gait, poorly coordinated movements, worse without vision
-crude touch preserved, also with parietal damage
Identify how to test for prosition sense
- subjects close eyes, passively move limb and ask patient to report whether its moved, and direction
-Move different joints for differnt dermatomes, hold on sides so pressure not indicating direction
Identify how to test vibration sense
-apply something vibrating on the skin- e.g. tuning fork and see they if they feel vibration
Identify how to test light (discriminatory) touch
use a soft or blunt object (cue tip or end of a matchstick) and drag along skin, see whether they can feel it and identufy direction. Can also use two point discrimination, e.g. ends of a paper clip and descriminate between sources of infor (one or two points?)
Describe tabetic (ataxic) gait and characteristics (PC-ML pathway)
e.g. due to disease, loss of proprioception in legs. Characteristics: high stepping, foot flapping (foot hands heal first and foot slaps down or land flat footed)
Damage to primary sensory neurons (of PC-ML pathways- somewhere as coming into spinal cord) can cause
loss of deep tendon reflex (hyporelexia)- reflex pathway relys on afferent side and efferent side. If damage afferent parthway, spindle stretch info not going to get into spinal cord
Damage above spinal cord level, deep tendon reflexes ______
intact
Negative symptoms of somatosensory lesions (spinothalamic pathway- anterolateral)
-loss of pain and temperture sensation
-reduced touch sensation
Describe how to test for pain sensation
use sharp object and lightly touch against skin, do they feel the sharp object alomg dermatome?
Describe how to test for temperature sensation
touch hot and cold object along dermatome, do they feel it, hot, cold or both
positive symptoms
in addition to loss of sensations have presence of abonormal sensations
two different catagories of abonormal sensations (positive symptoms)
-parastesia (dysesthesia) abnormal sensations but not painful e.g. tingling, numbness, tighness, pins and needles in dermatome
-hyperpathia/allodynia-painful sensation
parastesia (dysesthesia) related to damage to _____
PC-ML pathway
Differentiate hyperpathia and allodynia
hyperpathia- excessive painful sensation to normally painful stimuli
allodynia- pain sensation to stimuli not normally painful
hyperpathia/allodynia associated with damage to _____
anterolateral pathway
PC-ML pathway symptoms
e.g. tingling, numb sensation
anterolateral pathway symptoms
sharp, burning or searing pain
symptoms assoicated with damage to primary sensory neuorn (ie. nuclei, nerve root)
redicular pain, numbness and tingling (throughout dermatome)
