Lecture 4 Flashcards
what are the main long tracts in the nervous system?
lateral cortico-spinal tract (motor)
posterior columns (sensory–vibration, joint position, fine touch)
anterolateral pathways (sensory–pain, temp, crude touch)
motor system (corticospinal tract) composed of UMN and LMN (two-neuron system)
ye
study slide 6
ye–the cortical origin for most motor pathways = primary motor cortexx; cortical termination for most primary somatosensory info is the primary somat. cortex
remember the x-sectional organization of the spinal cord; central gray matter and peripheral white matter
ye
describe the structure of greay matter in the spinal cord
dorsal/posterior horn for SENSORY
intermediate visceral horm for VISCERAL MOTOR
ventral - anterior horn = motor
describe organization of white matter
white matter regions called funiculi
in x-section their are 3 major areas: – post funiculus, dorsal column; lateral fun (lateral column); anterior funiculus (ventral column)
study slide 10
ye
impaired motor control symptoms?
weakness, paralysis, wasting, jerking, incoordination
spinal nerves control upper and lower limb, cranial nerves control face
ye
supplementary motor area functions to coordinate complex sequences of movement; transform potentiona motor actions into real movements (self initiated movement)
premotor cortex functions to integrate visual and somatosensory cues; potential motor actions driven by sensory input
ye
UMN vs LMN?
UMN: neuron that projects from the cerebral cortex to LMN in brainstem or anterior horn of spinal cord (corticobulbar or cortical spinal projections wheraeas LMN are PERIPHERAL nerves of the spinal cord/brainstem which originate in the anterior/ventral horn of teh spinal cord gray matter/brainstem to effector organs, like muscle
REMEMBER: UMNS DECUSSATE at the PYRAMIDS
describe the major descending tract projections
divided into two systems
85% of axons descend to brainstem and decussate at the pyramids (lateral) and travel into contralateral funiculus (lateral corticospinal tract)–>controls rt & lt; info remains unilateral
the other 15% of the UMNs DON’T decussate but travel the anteromedial spinal cord path–>therefore they are called the medial cortical spinal tract (control the core); info from UMNs innervate LMN bilaterally;
CLINICALLY RELEVANT bc any lesion that is limited to one side of the motor system will have a profound effect for the contralateral lateral CST but not the anterior CST or other medial motor systems
study slide 26
ye
motor control is primarily from the contralateral cerebral hemisphere. what are the exceptions?
- the AXIAL muscle (close to the median line) are controlled by the same side of the hemisphere (controlled by the medial motor system)
- the facial motor nucleus
- complex movement involved both limbs which requires both hemis
what are the strongest intrahemispheral connections?
the ones connecting the:
-control of vertebral and abdominal musculature
they are routinely used bilaterally (connected?)
what are the weakest intrahemispheral linkages (commissural linkages)
controlling limb muscles (do not wanted strongly connected movements–e.g. play piano)
-routinely used independentl
what is imporant about the internal capsule (post limb)
where all tracks ascend and descend –> infarct here will knock out motor and sensory for one side of the body
study slide 30
ye
the lateral corticospinal tract UMN runs from the frontal/parietal cortex (precentral gyrus) to the internal capsule (still in the cortex) to the BASIS PEDUNCULUS in the midbrain, to the BASIS PONTIS in the pons; from the basis pontis it runs to the pyramid in the rostral medulla; it DECUSSATES in the cervicomedullary junction and further travels down the dorsal white matter; synapses with LMN in anterior horn gray matter
all UMNs from the lateral corticospinal tract converge in the internal capsule
what is the internal capsule made up of?
white matter; makes sense because the internal capsule is where all the axons (ascending and descending) converge, and white matter = axons
what is a lacunar infarct?
infarct in internal capsule–all tracts ascend and descend, lost of motor and sensory for one side of the body; location determines functional deficit
important to get to emerge asap!
describe weakness in a upper vs lower MN lesion
weakness is apparent in UMN lesions, after spastic paralysis subsides
weakness is also apparent in LMN lesions (flaccid paralysis)
describe atrophy in UMN vs LMN lesion
not apparent in UMN lesions (in the long run it is) but is apparent in LMN lesions
fasciculations in UMN vs LMN lesions?
not in UMN, present in LMN
