SOMATOSENSORY CORTEX AND PATHWAYS

Question 1

Somatosensation

Answer 1

• Position
• Vibration
• Fine touch
  Pressure
• Pain
• Temperature
• Gross touch

Question 2

General Somatosensory Pathway

Answer 2

• 1st order neuron
• Cell bodies in spinal dorsal root ganglion
• Receive sensory information from peripheral body regions
• 2nd order neuron
• Cell bodies either in the spinal cord or in the brain stem
• Fibers decussate and ascend to contralateral _Thalamus______________
• 3rd order neuron
• Fibers project from thalamus ipsilaterally to
  _____Primary Somatosensory Cortex_______________________

Question 3

Somatosensory Pathway:
Dorsal Column-Medial Lemniscal System

Answer 3

Fine discriminative touch
* Conscious proprioception
* Kinesthesia
* Decussation at ___Brainstem Medulla___________________

Question 4

Somatosensory Pathway:
Anterolateral System
* Divided into

Answer 4

Divided into
* Lateral spinothalamic tract
* Pain, temperature

• Anterior spinothalamic tract
• Diffuse, unlocalized, crude touch
• Decussation at _Spinal Cord_______________

Question 5

Parietal Association Area

Answer 5

Interpretation/integration of sensory experiences
* Superior parietal lobule
* Spatial orientation
* Awareness of external space
* Body schema
* Constructional skills

• Inferior parietal lobule
• _ANGULAR GURYS AND SUPRAMARGINAL GYRUS____________________________________
• Integration of visual-auditory and visual-tactile-auditory information for
  linguistic tasks
• Implications for reading and writing/spelling

Question 6

Hemispatial Neglect

Answer 6

Hemispatial Neglect
Deficit in awareness of or
attention to one side
of the field of vision

Question 7

• Tactile Agnosia

Answer 7

Inability to recognize objects through touch

Question 8

Primary Motor Cortex

Answer 8

Where?
* Efferent impulses from here synapse with lower motor
neurons in SC and ultimately innervate specific muscles:
Skeletal muscles

Question 9

Pyramidal Tract

Answer 9

Motor efferent signals sent from cortex to pass
through Pyramids of medulla
* Major voluntary pathways for all movement
* 2 tracts
* Corticospinal tract
* Corticobulbar tract

Question 10

Corticospinal Tract

Answer 10

A white matter motor
pathway starting at the
cortex that terminates
on motor neurons in the
spinal cord, controlling
movements of
The limbs and trunk _________________.

Question 11

(Lateral) Corticospinal Tract
Signal pathway

Answer 11

Motor cortex  Corona
radiata  Internal
capsule  Midbrain 
Pons  Medulla 
Spinal cord
* Decussation at medulla

Question 12

Corticobulbar Tract

Answer 12

A white matter motor
pathway connecting the
motor cortex in the
cerebral cortex to the
Medullary pyramids,
controlling muscles of
__face and head via cranial nerves __________________

Question 13

Corticobulbar Tract
Signal pathway

Answer 13

Lower 1/3 of motor
cortex  Internal capsule
 brainstem  Synapse
on cranial nerves

• Decussation at brain
  stem
• Bilateral vs Contralateral

Question 14

Movement: Points of Synapse
Upper and lower neurons, from where to to where ?

Answer 14

Upper motor neurons: Cortex
to spinal cord/brainstem

• Lower motor neurons: spinal
  cord/brainstem to
  neuromuscular
  junction/motor endplate

There are distinct patterns of
deficit depending on where in
the system damage occurs

Question 15

Signs of UMN vs. LMN lesions
UMN damage

Answer 15

UMN damage
* Hypertonicity
* Flaccidity turns to spasticity, hemiplegia/hemiparesis
* Hyper-reflexia (hyper-active reflexes)
* Upgoing plantar reflex (Babinski sign)

Question 16

Signs of UMN vs. LMN lesions
LMN damage

Answer 16

LMN damage
* Reduced tone
* Persistent flaccid paralysis
* Decreased/absent reflexes
* Marked muscular atrophy
* Fasciculations (muscle twitches)
Babinski sign