descending motor pathways

Question 1

motor system evolution

Answer 1

1. reticular formation
2. vestibular system
3. tectum
4. red nucleus
5. cerebral cortex
6. (later) pyramidal tract

Question 2

reticular formation

Answer 2

random network of neurons that has a reticulospinal pathway that modifies excitability of neurons in the spinal cord

Question 3

vestibular system

Answer 3

semicircular canals give us position in space, in relation to gravity
(up vs down)

Question 4

tectum

Answer 4

contain superior and inferior colliculus for visual and auditory inputs

Question 5

red nucleus

Answer 5

• primitive corticospinal tract
• has excitatory and controlling affects on more distal muscles

Question 6

cerebral cortex

Answer 6

controlled lower stations in the motor pathway

Question 7

somatotopic organization of ventral horn

Answer 7

more medial the muscle, the more medial the neurons are in gray matter

Question 8

descending pathways

Answer 8

• lateral pathways
• medial pathways

Question 9

lateral pathways control

Answer 9

distal musculature
- include: lateral corticospinal tract
skilled muscle movement

Question 10

medial pathways control

Answer 10

axial and proximal musculature
- include: vestibulospinal, reticulospinal, tectospinal tracts

Question 11

cells of motor cortex

Answer 11

giant pyramidal cells

Question 12

physiology of motor cortex

Answer 12

• pyramidal cell fires impulses prior to muscle movement
• organized to produce simple movements of individual body parts
• determines direction, amplitude, speed and force of movement
• not organized to control individual muscles

Question 13

somatotopy of motor cortex

Answer 13

motor area given to parts of the body that perform more precise and delicate movements compared to those that perform less precise movements
- movements not muscles!!

Question 14

efferent pathway

Answer 14

• axons thru white matter
• to internal capsule
• to crus cerebri/cerebellar peduncle
• pyramidal fibers pierce the pons
• pyramids of medulla
• lateral corticospinal tract

Question 15

other parts of the cerebral cortex that is involved with motor function

Answer 15

• premotor cortex
• supplementary motor cortex

Question 16

premotor cortex

Answer 16

• affects motor cortex
• organizes neurons into more complex units of movement
• triggers movement of response to visual and other stimuli
• directs reaching and grasping movements
  “preparation of movement”

Question 17

supplementary motor cortex

Answer 17

• higher level of motion control
• concerned with mvmt that is self generated
• bilateral movements

Question 18

corticobulbar tract

Answer 18

• cell bodies in motor cortex (lateral convexity)
• fibers leave through internal capsule
• exit in midbrain, pons, and medulla
• innervate cranial nerve motor nuclei
• crossed and uncrossed fibers
  (motor cortex to cranial nerve nuclei)

Question 19

corticobulbar tract interacts with these nuclei:

Answer 19

• trigeminal motor nucleus
• nucleus ambiguus
• facial motor nucleus (upper face)
• facial motor nucleus (lower face)
• hypoglossal nucleus

Question 20

which nuclei have completely crossed tracts? (control contralateral sides)

Answer 20

• facial motor nucleus (lower face)
• hypoglossal nucleus

Question 21

abducens and facial nerves

Answer 21

Question 22

bell’s palsy symptoms

Answer 22

• droopy eyelid, dry eye, or excessive tears
• facial paralysis, twitching, weakness
• drooping corner of mouth, dry mouth, impaired taste

Question 23

bell’s palsy can be caused by

Answer 23

lesion of CN VII
- lesion on left side = paralysis of left side of face

Question 24

lower face nucleus receive input from

Answer 24

opposite side motor cortex face area only

Question 25

the upper face gets inputs form

Answer 25

same side AND opposite side motor cortex

Question 26

what if there is a lesion of motor cortex on opposite side?

Answer 26

• the axons will degenerate
• lost control of lower part of the face
• still have control of the upper half of the face bc it also receives same side signals

Question 27

why is it bad if only the lower half of the face lost motor function?

Answer 27

• indicative of a stroke in dangerous area
• disrupted the cranial nerve (7?)
• motor cortex damages

Question 28

jacksonian march

Answer 28

the spreading of seizure from primary location to other parts of the body (I.e. from thumb to face)

Question 29

epilepsy is the result of

Answer 29

excessive activity of neurons
- opposite of a lesion

Question 30

upper motor neuron lesion

Answer 30

• slight muscle atrophy
• no fasciculation
• hyperreflexia
• increased/spastic muscle tone

Question 31

lower motor neuron lesion

Answer 31

• severe muscle atrophy
• fasciculation
• hyporeflexia
• decreased/flaccid muscle tone

Question 32

spastic hemiplegia cause

Answer 32

stroke of left hemisphere

Question 33

symptoms of spastic hemiplegia

Answer 33

• arm is flexed upward
• knee is straight out
• fingers are curled due to hyperactivity of stretch reflexes
• excess tone due to UMN lesion (no descending inhibition to blow out unnecessary reflexes

Question 34

Babinksi Response Test

Answer 34

• in babies less than 1 year
• run finger along bottom of foot
• toes will flare and withdraw foot

Question 35

when is the Babinski reflex suppressed?

Answer 35

• after 1 year of age
• helps ability to walk
• not present in adults (curl toes instead)

Question 36

grasp reflex

Answer 36

• when anything touches a baby’s palm, fingers close
• reflex is outgrown unless damage to motor cortex