Thursday 2 - Ruff - Motor cortex

Question 1

Stellate cells

look like
recieve input from
are in the

Answer 1

small round cells
recieve thalamocortical input
in the granular cortex

Question 2

pyramidal cells

where do they project out of

Answer 2

cortex

Question 3

what layer of the motor cortex projects out to the spinal cord?

Answer 3

Layer 5

bonus - motor cortex has a big layer 5 and a small layer 4

Question 4

what large cells are found at high concentration in layer 5 of the motor cortex?

Answer 4

Betz cells, larger versions of pyramidal cells

Question 5

brodmann’s primary visual cortex

Answer 5

17

Question 6

brodmans area 4

Answer 6

precentral gyrus, primary motor cortex

Question 7

What brodmanns area is directly anterior to the precentral gyrus

Answer 7

6, premotor cortex and suplimentary motor are

Question 8

Brodmanns area 8

Answer 8

frontal eye fields in the posterior part of the frontal lobe. Recieves projections from the posterior part of the occipital lobe (brodmans 17)

Question 9

eye movements as vectors:

where is the horizontal gaze center in the brain? Where do they go to get to the eyes?

vertical gaze center?

Answer 9

PPRF - paramedian pontine reticular formation (goes ipsilateral to abducens, contra to CN III via medial longitudinal fasciculus

Rostral interstitial nucleus of the medial longitudinal fasciculus

Question 10

Injury to the left frontal eye field (FEF) results in what

Answer 10

loss of voluntary saccades to the right

Inability to move gaze away from a stimulus that your superior colliculus (involuntary) wants you to look at.

Question 11

what region of the brain is responsible for the involuntary saccade that is a response to a bright light in the perhipheral vision field?

Answer 11

superior colliculus

Question 12

Proprioceptive info pathway to the brain

Answer 12

contralateral periphery (like your finger)
dorsal column nuclei
VPL thalmus

Question 13

What part of the brain is associated with the idea of “I’m going to put my hand there because there is a light there”

What part of the brain is involved in the INTERNAL generation (not a response to external stimuli like a light) of a movement. “I’m going to get out of my chair because it is the first step towards my eventual goal of making a pizza”

Answer 13

pre-motor cortex

supplementary motor area

Question 14

lesions to the premotor cortex

Answer 14

loose the ability to respond properly to stimuli i.e. if they are handed a toothbrush they wont know how to use it.

monkey will not be able to reach under plexiglass to get food

if “go” was changed to purple from green, someone with a premotor lesion would not know what the frig to do.

Question 15

Stimulation of supplementary motor area does what

Answer 15

evokes motion in multiple joints (less joints that premotor cortex, but more than primary motor cortex)

postural changes

Question 16

part of the brain involved in learning sequences of movements, performing sequences of learned movements, and mental rehersal?

Answer 16

Supplementary motor area

Question 17

what happens when you get a lesion in the supplementary motor area?

three main conditions

Answer 17

Loss of volitional (internally driven) movements:

Loss of suppression of motor programs:

• Alien hand syndrome - contralateral “semi-purposeful movements that are ouside of patient’s volitional control
• Utilization behavior: use of objects in an inappropriate setting i.e. picking up someone elses hair brush and using it

loss of non suppresional motor programs:

neglect of affected limb i.e. they forget that their left arm is even there but can use it when told to

Question 18

difference between premotor cortex and supplementary motor cortex`

Answer 18

premotor - thinking about going through the motions of a certain sequence of movements

supplementary - going through the motions of a certain sequence of actions

Question 19

basic pathway of the corticospinal tract

Answer 19

from primary motor, premotor, supp motor, somatosensory cortex to:

internal capsule

cerebral peduncle

ventral pons

pyramidal tracts on the ventral medulla

once it reaches the pyramidal decussation, 90% of the fibers decussate to form the lateral corticospinal tract (the 10% that dont form the ventral (anterior) corticospinal tract

Question 20

Rubrospinal tract

nucleus associated with it?

parts of it

Answer 20

Red nucleus - right next to the superior colliculus

recieves input from the magnocellular nucleus - input from motor cortex, output to spinal cord.

parvocellular - input from cerebellum, output to inferior olive

Question 21

This motor tract is involved in the control of the arms, and is more developed in infants and lower vertebrates than adult humans

Answer 21

rubrospinal tract

Question 22

Vestibulospinal tracts

inputs

two nuclei
-purpose of both

Answer 22

inputs - vestibular organs, cerebellum

Medial vestibular nucleus - regulates head position (terminates bilaterally in the medial ventral horn)

lateral vestibular nucleus - Activates physiological extensor muscles when deviations from stable posture occur

Question 23

reticulospinal tracts

two nuclei and what they do

Answer 23

(reticulo- refers to an area without a defined border)

Pontine reticular formation - excites gamma - increases tone
inhibited by cortex

medullary reticular formation -
inhibits gamma - decreases tone
excited by cortex

coordinate movements of the trunk and proximal limbs i.e. hips, shoulders

the net effect of the reticulospinal tract is increased tone

Question 24

what part of your brain looks at a dart you just threw and says “you were off by X inches, change the motor output next time.”

Answer 24

cerebellum

Question 25

tonic activity of _______ motor neurons leads to posture

Answer 25

alpha

Question 26

an “indirect” way to stimulate alpha motor neurons

Answer 26

increasing gamma motor neuron activity

Question 27

With regards to the corticoreticular and reticulospinal tracts, the activity in the cortex results in a _______ in gamma motor activity, leading to a _______ in muscle tone

Answer 27

decrease

decrease

Question 28

what happens when you lesion the pyramids of the spinal cord?

what compensates and how?

Answer 28

loss of fine motor use of the hands

rubrospinal tract, reticular spinal tract, vestibulo spinal tract can all compensate for gross muscle movements but they cannot compensate for the fine movements of the hands

Question 29

when motor neurons haven’t been innervated for a while, what do they do?

Answer 29

increase the amount of receptors on their dendrites

Question 30

what develops in adults, resulting in loss of positive babinskies

Answer 30

corticospinal tract and myelin

Question 31

what part of the spinal cord does the rubrospinal tract project to?

Answer 31

cervical spinal cord (flexion of upper limbs)

Question 32

What can you snip in a patient with overactive muscle activity and pain e.x. cerebral palsy

Answer 32

the dorsal root of the afferent neuron coming from the muscle (the 1a afferent specifically, if you can)

This reduces the cycle of spacicity

Question 33

decorticate posture

what is lesioned
clinical signs

Answer 33

get from UMN leasion
brainstem centers are intact, but not getting modulatory info from the cortex. dmg is above the level of the red nucleus.

upper extremity flexion
lower extremity extension

Question 34

decerebrate posture

what is lesioned
clinical signs

Answer 34

loss of red nucleus, progression of decorticate posture

all limbs in extension
no modulation of reticulospinal tract

medical emergency - if lesion continues then you get loss of vestibulo and reticulospinal paths, leads to faccidity and likely death