Lecture 4

Question 1

what are the main long tracts in the nervous system?

Answer 1

lateral cortico-spinal tract (motor)

posterior columns (sensory–vibration, joint position, fine touch)

anterolateral pathways (sensory–pain, temp, crude touch)

Question 2

motor system (corticospinal tract) composed of UMN and LMN (two-neuron system)

Answer 2

ye

Question 3

study slide 6

Answer 3

ye–the cortical origin for most motor pathways = primary motor cortexx; cortical termination for most primary somatosensory info is the primary somat. cortex

Question 4

remember the x-sectional organization of the spinal cord; central gray matter and peripheral white matter

Answer 4

ye

Question 5

describe the structure of greay matter in the spinal cord

Answer 5

dorsal/posterior horn for SENSORY
intermediate visceral horm for VISCERAL MOTOR
ventral - anterior horn = motor

Question 6

describe organization of white matter

Answer 6

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)

Question 7

study slide 10

Answer 7

ye

Question 8

impaired motor control symptoms?

Answer 8

weakness, paralysis, wasting, jerking, incoordination

Question 9

spinal nerves control upper and lower limb, cranial nerves control face

Answer 9

ye

Question 10

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

Answer 10

ye

Question 11

UMN vs LMN?

Answer 11

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

Question 12

describe the major descending tract projections

Answer 12

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

Question 13

study slide 26

Answer 13

ye

Question 14

motor control is primarily from the contralateral cerebral hemisphere. what are the exceptions?

Answer 14

• 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

Question 15

what are the strongest intrahemispheral connections?

Answer 15

the ones connecting the:

-control of vertebral and abdominal musculature

they are routinely used bilaterally (connected?)

Question 16

what are the weakest intrahemispheral linkages (commissural linkages)

Answer 16

controlling limb muscles (do not wanted strongly connected movements–e.g. play piano)

-routinely used independentl

Question 17

what is imporant about the internal capsule (post limb)

Answer 17

where all tracks ascend and descend –> infarct here will knock out motor and sensory for one side of the body

Question 18

study slide 30

Answer 18

ye

Question 19

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

Answer 19

all UMNs from the lateral corticospinal tract converge in the internal capsule

Question 20

what is the internal capsule made up of?

Answer 20

white matter; makes sense because the internal capsule is where all the axons (ascending and descending) converge, and white matter = axons

Question 21

what is a lacunar infarct?

Answer 21

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!

Question 22

describe weakness in a upper vs lower MN lesion

Answer 22

weakness is apparent in UMN lesions, after spastic paralysis subsides

weakness is also apparent in LMN lesions (flaccid paralysis)

Question 23

describe atrophy in UMN vs LMN lesion

Answer 23

not apparent in UMN lesions (in the long run it is) but is apparent in LMN lesions

Question 24

fasciculations in UMN vs LMN lesions?

Answer 24

not in UMN, present in LMN

Question 25

describe reflexes in UMN vs LMN lesions?

Answer 25

increased in UMN, decreased in LMN

Question 26

describe tone in UMN vs LMN lesions

Answer 26

present in UMN lesions, not in LMN

Question 27

describe paresis

Answer 27

weakness (very vague term)

Question 28

describe the suffix plegia

Answer 28

no movement

Question 29

describe the prefix para

Answer 29

means “both legs”

Question 30

hemiparesis = weakness on one side of body

Answer 30

ye

Question 31

describe the signs of UMN lesions

Answer 31

• muscle weakness
• hyperreflexia
• increased tone
• Babinski’s sign (fanning of toes)

Question 32

describe the signs of LMN lesions

Answer 32

• muscle weakness
• hyporeflexia
• decreased tone
• atrophy