Functional hierarchy of the motor system

Question 1

Motor control is a functional hierarchy with 3 levels:

+ name the parts of the brain/CNS associated with each level

Answer 1

High (strategy) - association areas, basal ganglia
Middle (tactics) - motor cortex, cerebellum
Low (execution) - brainstem, spinal cord

Question 2

Alpha motorneurons are also known as what neurons

Answer 2

LMNs

Question 3

4 components of the voluntary motor system

Answer 3

Descending control pathways
Basal ganglia
Cerebellum
Local spinal cord/brain stem circuits

Question 4

There’s lots of … input to local circuit neurons (formed by LMNs)

Answer 4

sensory input

Question 5

Spinal cord reverts descending input from… (2)

Answer 5

Brainstem AND cortical input via corticospinal tract

Question 6

Sensory input enters at different levels and is crucial in each: (3)

Answer 6

Spinal cord - in the form of proprioceptors nociceptors etc

Brainstem - vestibular system informs about balance

Cortical level - we make movements in repsonse to visual, olfactory, auditory cues etc

Question 7

Can descending inputs interact with segmental reflexes + if so, what are these descending inputs and how do they work

Answer 7

Yes

Brainstem nuclei can over-ride and exert control over spinal reflexes

Question 8

What does it mean by reflex control of muscles is autonomous

Answer 8

Means it happens whether you’ve got a brain or not, reflex control is hardwired into motor neurone circuits at each segmental spinal level

Question 9

What is the vestibulospinal tract involved in

Answer 9

Balance

Question 10

What is the reticulospinal tract involved in

Answer 10

Takes visual input and regulates trunk and limb muscle reflexes from this

Question 11

Brainstem nuclei can override spinal reflexes but where do they receive their control inputs about voluntary movements from

Answer 11

Higher centres - the cerebral cortex (motor cortex and premotor and supplementary motor areas), the basal ganglia and the cerebellum

Question 12

What tracts do the ventromedial pathways consist of (4)

Answer 12

Tectospinal tract
Vestibulospinal tract
Pontine reticulospinal tract
Medullary reticulospinal tract

Question 13

What is the tectospinal tract involved in

Answer 13

ensures eyes remain stable as body moves

Question 14

What 2 tracts control posture and locomotion

Answer 14

Vestibulospinal + tectospinal

Question 15

What 2 tracts control trunk and antigravity muscles

Answer 15

Pontine and medullary reticulospinal tracts

Question 16

What 2 white matter tracts do the lateral pathways consist of

Answer 16

Corticospinal

Rubrospinal

Question 17

What fraction of the corticospinal tract is motor and somatosensory

Answer 17

2/3 motor

1/3 somatosensory

Question 18

Where does the rubrospinal tract begin

Answer 18

Red nucleus in midbrain

Question 19

If there’s a lesion of the corticospinal tract, what tract can take over

Answer 19

Rubrospinal

Question 20

Neurons of the CST … excite pools of … motorneurons

The same neurons branch and via …, inhibit pools of … motorneurons

Answer 20

monosynaptically

agonist

interneurons

antagonist

Question 21

Medial LMNs control axial/proximal or distal limb muscles so medial tracts are more responsible for control of posture + balance or precise voluntary movements

Answer 21

axial/ proximal

Posture + balance

Question 22

Lateral LMNs control axial/proximal or distal limb muscles

Answer 22

Distal

Question 23

UMNs from brainstem travel in what pathways synapsing with LMNs in what part of spinal cord

Answer 23

Ventromedial

Lateral ventral horn

Question 24

UMNs from cortex travel in what pathways synapsing with LMNs in what part of spinal cord

Answer 24

Lateral pathways (CST & RST)

Medial ventral horn

Question 25

Premotor cortex (Area 6) subdivided in what 2 areas

Answer 25

Premotor area

Supplementary area

Question 26

Planning of movement by the cerebrum requires 3 things

Answer 26

Where the body is in space (proprioceptive and visual input)

Where it wants to go

Selecting a plan to get there

Question 27

What is area 7 of the brain

Answer 27

Visuo-motor co-ordination area

Question 28

Decision making, what movement to take + their likely outcome occurs in what areas of the brain (2)

Input from these 2 areas converges onto what area + what happens there

Answer 28

Prefrontal cortex
Somatosensory cortex

Area 6 - premotor cortex, signal is converted into how it’s going to be carried out by decision making neurons in area 6