4.17. Suprasegmental Motor control

Question 1

basic pathway of segmental control (starting from motor areas in the brain to the muscle groups)

axial muscles innervated by __ (ventromedial/dorsolateral) neurons

limb muscles innervated by __ (ventromedial/dorsolateral) neurons

Answer 1

Motor cortex, premotor areas and supplementary motor areas project down to the spinal cord (specifically either directly to the lower motor neurons in the ventral horn, or they project to interneurons that then project to groups of LMNs)

Axial muscles are innervated by the ventromedial motor neurons

Limb muscles are innervated by dorsolateral motor neurons

The lateral neurons doesn’t really exist at the thoracic level (obviously there’s no need for them); they only exist in the cervical and lumbar spine

**that little green interneuron circled in red projects to limb muscles and innervates multiple segments**

Question 2

3 types of motor skills in clinical medicine (plus examples of each)

Answer 2

Gross motor skills: walking, running, etc (so basically things that involve using major muscle groups)

Fine motor skills: writing

Visuo-motor skills: e.g. using blocks to build things (constructing; higher order functions compared to fine motor skills)

Question 3

descending motor pathways

Answer 3

Corticospinal Tracts

Corticobulbar Tracts

Rubrospinal Tracts

Tectospinal Tracts

Vestibulospinal Tracts

Reticulospinal Tracts

Question 4

pathways of descending motor pathways

(e.g. Corticospinal Tracts: Brain to S.C.)

Answer 4

Corticospinal Tracts: Brain to S.C.

Corticobulbar Tracts: Brain to brainstem

Rubrospinal Tracts: Red nucleus to S.C.

Tectospinal Tracts: Superior colliculus to S.C.

Vestibulospinal Tracts: Vestibular nuclei to S.C.

Reticulospinal Tracts: Reticular nuclei to S.C.

Question 5

LMNs to the face, head and neck are located in the ___

The LMNs to your limbs are located in the ___

Answer 5

brainstem

ventral horn of the spinal cord

Question 6

pathway of lateral corticospinal tracts

A lesion in the dorsolateral SC will cause weakness ___ (contralaterally or ipsilaterally)

Answer 6

cortex >> internal capsule >> cerebral peduncles >> basis pontis >> pyramids >> pyramidal decussation >> dorsolateral spinal cord (as lateral corticospinal tract) >> limb muscles

A lesion in the dorsolateral SC will cause weakness contralaterally

Question 7

pathway of anterior corticospinal tracts

a lesion in the anteromedial SC will cause weakness ___ (contralaterally/ipsilaterally)

Answer 7

cortex >> internal capsule >> cerebral peduncles >> basis pontis >> pyramids >> anteromedial spinal cord (as anteromedial spinal cord) >> axial muscles

Lesion in the anteromedial spinal cord will cause weakness ipsilaterally

Question 8

pathway of corticobulbar tracts

corticobulbar tracts control output to the ___, ___, and ___

Answer 8

These fibers start out in the cortex then go down the internal capsule (probably the genu), through the cerebral peduncles and from there, they could either continue downwards ipsilaterally or if they reach their target, they can cross at that level

face, head, neck

Question 9

nuclei of cranial nerves __, __ and __ receive bilateral innervation

Answer 9

Nuclei of cranial nerves 5, 7 and some of 12 receive bilateral innervation

Question 10

briefly describe the innervation of the facial nerve nucleus (differences between upper and lower face innervation)

Bell’s palsy (signs on the face; if forehead is affected or not)

what happens if you have a lesion in the motor cortex?

Answer 10

Lower face only has unilateral innervation; upper face has bilateral innervation

Bell’s palsy: LMN facial weakness; the entire face including the forehead is affected

If there’s a lesion in the motor cortex, you’ll get contralateral face weakness, but the forehead will be spared since it’s doubly innervated

Question 11

pathway of rubrospinal tracts

if you lost innervation through the corticospinal tracts, which functions would you preserve and which ones would you lose?

Answer 11

red nucleus >> (crossing at level of origin) >> pons >> medulla (raustral >>caudal) >> lateral anterior horn of spinal cord >> flexor muscles of limbs

preserve: gross motor functions
lose: fine motor functions

Question 12

tectospinal tract pathway

Answer 12

Superior colliculus >> (cross at level of origin) pons >> medulla >> (medial) cervical spinal cord >> axial muscles ( plus vision)

Question 13

function of tectospinal tracts

Answer 13

reflexive head movements related to eye movements

Question 14

vestibulospinal tract types

pathway of each

Answer 14

medial and lateral vestibulospinal tracts

Medial vestibulospinal tract descends bilaterally in the tegmentum; innervates the lower medulla and cervical spinal cord (anterior horn)

Lateral vestibulospinal tract descends unilaterally/ipsilaterally to the entire spine; innervates extensor muscles

Question 15

reticulospinal tract pathway

function of reticulospinal tract

Answer 15

Pontine reticular formation >> medulla >> (medial) cervical spinal cord

innervation of axial muscles most likely since its medial

Question 16

posture definition

2 components of posture

Answer 16

Posture: Position of a person’s body parts

Components:

Orientation – positioning of body parts in relation to each other

Balance – active resistance to external forces on the body

Question 17

sway (definition)

higher centers that control balance (3 of them)

Answer 17

sway: deviation of body position away from a stable equilibrium

• Vestibular system
• Cerebellum
• Cerebral cortex

Question 18

locomotion definition

role of central pattern generator; where does CPG activity come from?

Answer 18

ability to move in space

(Locomotion is basically automatically regulated (central pattern generators) )

spinal cord

Question 19

motor equivalence

Answer 19

The idea that motor cortex controls the task of motor function, but the actual action is up to other parts of the body

Question 20

In the primary motor cortex (precentral gyrus), the ___ and the ___ have the most representation because they do a lot of fine motor functions

3 main brain areas involved in voluntary movement

Answer 20

In the primary motor cortex (precentral gyrus), the hand and the face have the most representation because they do a lot of fine motor functions

Premotor cortex (right in front of the primary motor cortex); supplementary motor cortex in the interhemispheric fissure; primary motor cortex

Question 21

what are the sensory areas (near the motor areas) that are also involved in voluntary movement?

Answer 21

postcentral gyrus (primary somatosensory) and posterior parietal cortex (more higher order)

Question 22

other areas involved in voluntary movement (hint: the things he was saying were extra-pyramidal)

Answer 22

Basal ganglia

Thalamus

Brainstem

Cerebellum

(pyramidal tracts and extra pyramidal system)

Question 23

The ___ lobe is important for making a sensory picture of the world

Answer 23

posterior parietal lobe

Question 24

which area of the brain is linked to the posterior parietal lobe and is involved in making multiple sensory maps? (hint: its one of the 3 motor areas)

Answer 24

pre-motor cortex

Question 25

which area of the brain is responsible for executing voluntary movement?

Answer 25

frontal lobe (premotor cortex + prefrontal cortex)

Question 26

define readiness potential

Answer 26

Readiness potential: pre-set plan of action in your brain before you execute an action

Question 27

coordination of muscle movements following the firing of motor neurons is done at the level of the ___

Answer 27

spinal cord