Lecture 10

Question 1

Anterolateral pathway consists of which ascending pathways

Answer 1

-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

Question 2

Describe the anteriolateral pathways

Answer 2

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.

Question 3

Identify this pathway

Answer 3

anterolateral pathway

Question 4

Identify this pathway

Answer 4

anterolateral pathway

Question 5

Identify this body part

Answer 5

neck

Question 6

Identify this body part

Answer 6

arm

Question 7

Identify this body part

Answer 7

trunk

Question 8

Identify this body part

Answer 8

leg

Question 9

Describe somatotopic organisation of antero-lateral pathway

Answer 9

leg (distal regions)= lateral
arms= medial
As go up the body sgements layer in medially

Question 10

Describe the thalamus

Answer 10

-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

Question 11

Identify this

Answer 11

thalamocortical and corticothalamic projections

Question 12

Identify this

Answer 12

basal ganglia

Question 13

Identify this

Answer 13

limbic system

Question 14

Identify this

Answer 14

reticular formation

Question 15

Identify this

Answer 15

cerebellum

Question 16

Identify this

Answer 16

somatosensory, auditory, visual, vestibular and other inputs

Question 17

Primary sensory cortex makes up _______

Answer 17

post central gyrus

Question 18

Identify this

Answer 18

somatosensory homunculus

Question 19

Identify this

Answer 19

motor homunculus

Question 20

Describe the organsiation of the primary somatosensory cortex

Answer 20

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

Question 21

“negative” symptoms

Answer 21

subtraction/removal od normal sensation

Question 22

Negative symtoms of somatosensory lesions- PC-ML pathway

Answer 22

-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

Question 23

Identify how to test for prosition sense

Answer 23

• 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

Question 24

Identify how to test vibration sense

Answer 24

-apply something vibrating on the skin- e.g. tuning fork and see they if they feel vibration

Question 25

Identify how to test light (discriminatory) touch

Answer 25

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?)

Question 26

Describe tabetic (ataxic) gait and characteristics (PC-ML pathway)

Answer 26

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)

Question 27

Damage to primary sensory neurons (of PC-ML pathways- somewhere as coming into spinal cord) can cause

Answer 27

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

Question 28

Damage above spinal cord level, deep tendon reflexes ______

Answer 28

intact

Question 29

Negative symptoms of somatosensory lesions (spinothalamic pathway- anterolateral)

Answer 29

-loss of pain and temperture sensation -reduced touch sensation

Question 30

Describe how to test for pain sensation

Answer 30

use sharp object and lightly touch against skin, do they feel the sharp object alomg dermatome?

Question 31

Describe how to test for temperature sensation

Answer 31

touch hot and cold object along dermatome, do they feel it, hot, cold or both

Question 32

positive symptoms

Answer 32

in addition to loss of sensations have presence of abonormal sensations

Question 33

two different catagories of abonormal sensations (positive symptoms)

Answer 33

-parastesia (dysesthesia) abnormal sensations but not painful e.g. tingling, numbness, tighness, pins and needles in dermatome -hyperpathia/allodynia-painful sensation

Question 34

parastesia (dysesthesia) related to damage to _____

Answer 34

PC-ML pathway

Question 35

Differentiate hyperpathia and allodynia

Answer 35

hyperpathia- excessive painful sensation to normally painful stimuli allodynia- pain sensation to stimuli not normally painful

Question 36

hyperpathia/allodynia associated with damage to _____

Answer 36

anterolateral pathway

Question 37

PC-ML pathway symptoms

Answer 37

e.g. tingling, numb sensation

Question 38

anterolateral pathway symptoms

Answer 38

sharp, burning or searing pain

Question 39

symptoms assoicated with damage to primary sensory neuorn (ie. nuclei, nerve root)

Answer 39

redicular pain, numbness and tingling (throughout dermatome)