Lecture 17+18 DLA 20+21

Question 1

what layer of the brain is important?

Answer 1

Layer 5 (pyramidal cells)

these cells communicate directly and indirectly with lower motor neurons (brainstem/spinal cord)

Question 2

what are the BA’s of the somatosensory cortex?

Answer 2

BA 1, 2, and 3

Question 3

Role of BA’s 5 and 7

Answer 3

posterior parietal cortex

integrates sensory information for motor planning in concert with premotor areas

Question 4

role of medial and lateral premotor areas

Answer 4

medial:
involved in planned sequences

lateral:
sensory guided movements

Question 5

route of the tracts

Answer 5

corona radiata
internal capsule (corticospinal) (posterior limb)
crus cerebri
pons

corticobulbar pass through the genu

Question 6

fiber locations in the crus cerebri

Answer 6

corticospinal: within the middle 3/5 of the crus cerebri
corticobulbar: located medial to the corticospinal fibers

Question 7

spinal shock

Answer 7

occurs with bilateral damage to the spinal cord

initial lower motor neuron symptoms
upper motor neuron symptoms are seen after 4 week of injury

Question 8

lesion above the decussation?

Answer 8

signs are contralateral to the lesion

Question 9

lesion below the decussation?

Answer 9

signs are ipsilateral to the lesion

Question 10

spinal cord transection (paraplegia)

Answer 10

flaccid paralysis below the level of the lesion

upper motor neuron signs

loss of all somatosensory perception below the lesion

Question 11

rubrospinal tract

Answer 11

arises from the neurons in the red nucleus
has cortical input

action: flexion of the upper limbs

crosses the midline at the midbrain

synapse with alpha and gamma motor neurons in the dorsal part of the ventral horn

cervical spinal cord

Question 12

medullary (lateral) reticulospinal tract

Answer 12

arise from the magnocellular neurons located in the middle 2/3 of the medulla

function: powerfully suppress extensor spinal reflex activity and contract the flexors

all levels of spinal cord

Question 13

Pontine (medial) reticulospinal tract

Answer 13

arise from pontine reticular nucleus
has bilateral cortical input

effect: axial and limb extensors

Question 14

spinoreticular tract

Answer 14

sensory pathway ( collateral anterolateral system)

relays sensory info to reticular nuclei about pain, temp, and touch (trunk and limbs on opposite sides)

Question 15

lateral vestibulospinal tract

Answer 15

arise from the lateral vestibular nucleus
no cortical input
input from inner ear and cerebellum

does not cross; extends whole spinal cord

synapse with alpha motor neurons of limb extensors

Question 16

medial vestibulospinal tract

Answer 16

arises from the medial vestibular nucleus
no cortical input

input from inner ear and cerebellum
descend on same side

synapse with alpha motor neurons in the cervical and upper thoracic levels

muscular contraction of neck and eye movement

Question 17

decorticate posturing

Answer 17

upper limbs flexed and lower limbs extended

lesion above the red nucleus

corticospinal and corticobulbar fibers interrupted

Question 18

Decerebrate posturing

Answer 18

upper and lower limbs are extended

lesion is below the red nucleus

corticospinal, corticobulbar, and rubospinal interrupted

Question 19

role of the muscle spindle

Answer 19

1. stretch or myotatic reflex
2. proprioceptive info to the CNS
3. regulates muscle contraction