control of movement

Question 1

what are the 3 key levels to movement control

Answer 1

1. spinal chord;
2. motor cortex;
3. cerebellum + BG;

Question 2

3 classifications of movement

Answer 2

1. simple reflexes;
2. rhythmic motor patterns (initiation/termination are voluntary but actual action is reflexive);
3. volunatry;

Question 3

4 key players in simple reflexes

Answer 3

1. golgi tendon organs;
2. muscle spindles;
3. afferent/efferent neurons;
4. interneurons

Question 4

interneuron role

Answer 4

provide basic level processing through selective excitation/inhibition of motor neurons e.g. coordination of flexors and extensors within same limb

Question 5

what does the patella reflex aid with

Answer 5

walking -> selectively excites hamstrings but inhibits quadriceps

Question 6

what are central pattern generators

Answer 6

self-organizing biological neural circuits that produce rhythmic outputs in the absence of rhythmic input -> movements can be sustained indefinitely at SC level after initial initiation e.g. walking, breathing

Question 7

what neurons are key in central pattern generation

Answer 7

inter neurons -> selective excitation/inhibition of muscles

Question 8

how do central pattern generator neurons work (2)

Answer 8

1. pacemaker/follower
2. reciprocal inhibition
   CPGs may be a combination of both

Question 9

explain the pacemaker/follower mechanism (central pattern generation)

Answer 9

certain neurons act as core oscillators where they create their own intrinsic APs (leaky channels), these cells are coupled to others and cause depol in them when they themselves depol

Question 10

explain reciprocal inhibition (central pattern generation)

Answer 10

one neuron fires which also causes inhibition in another neuron to which it is coupled => it cannot fire -> the inhibition eventual wears off and the second nerve can now fire -> causes inhibition of the first neuron -> leads to rhythmic pattern of firing

Question 11

what are the 2 major motor pathways in the motor cortex

Answer 11

1. corticospinal (goes to SC to cause movement of body);
2. corticobulbar (movement of head, neck and face);

Question 12

what is the function of the pre motor cortex

Answer 12

motor planning, works alongside the BG

Question 13

what is the function of the supplemenatry motor area

Answer 13

complex sequence planning; skill learning; movement based on sensation; bilateral movement

Question 14

corticospinal tract pthaway (M1 -> SC)

Answer 14

motor cortex -> midbrain -> cerebral peduncles -> pons -> pyramids (brainstem) -> decussation (in oyramids) for 90% -> lateral corticalspinal tract (distal msucles)

for those that dont dessucate: pyramids -> ventral/anterior corticospinal tract (proximal muscle) -> decussate in DH -> sunampse to LMN

Question 15

4 symptoms of UMN lesions

Answer 15

1. weakness in muscles;
2. hyperactive reflexes;
3. decreased motor control -> loss of fine muscle movements;
4. abnormal muscle tone

Question 16

what is the role of the BG in movement

Answer 16

smooths out movement (tremor), movement motivation

Question 17

role of cerebellum in movement (3)

Answer 17

1. error correction -> distinction between desired/planned movement and the actual movement;
2. maintain muscle tone;
3. balance/stability

Question 18

what is the BG direct pathway (draw out!)

Answer 18

motor cortex → glutaminergic activation of dorsal striatum (caudate nucleus and putamen) → D1 route activation (this is also activated by dopamine release from the SNc, this is the largest dopamine pathway and is known as the nigrostriatal pathway) → substance P/ GABA release causes inhibition of GPi and SNr → decreases GABAergic inhibition of thalamus (aka excitation) → execution of the action can occur

Question 19

BG indirect pathway (draw out!)

Answer 19

motor cortex → glutaminergic activation of the dorsal striatum (corticospinal tract) → D2 route activation → enkephalin release causes inhibition of GPe → inhibition of STN → excitation of GPi → inhibition of thalamus → inhibition of movement

Question 20

what is the role of the substantia nigra

Answer 20

releases DA

Question 21

role of the BG indirect pathway

Answer 21

smooths movement (downregulated unwanted movements)

Question 22

what are the 3 peduncles of the cerebellum and what do they do

Answer 22

Superior peduncle: this connects the cerebellum to the midbrain (colliculi, tegmentum etc.) and allows for deep cerebellar nuclei to communicate with the motor cortex (via the thalamus)

Middle peduncle: connects cerebellum to the pons and receives input from the cerebral cortex

Inferior peduncle: connects cerebellum to medulla, input from proprioceptors and vestibular receptors, outputs to upper motor neurons (non-sc neurons)

Question 23

what structures does the BG comprise of (3)

Answer 23

1. striatum (caudate nucleus, nucleus Accumbens and the putamen)
2. the globus pallidus
3. some also include the substantia nigra and subthalamic nuclei

Question 24

what separates the cerebellum from the occipital lobe

Answer 24

the cerebellar tentori

Question 25

what area does the cerebellum sit in?

Answer 25

posterior cranial fossa

Question 26

what does the flocculonodular lobe of the cerebellum do

Answer 26

vestibular movement (balance + eye movements) -> gets info from CN VIII

Question 27

what is another name for the flocculonodular lobe

Answer 27

vestibulo-cerebellar

Question 28

what is the vermis (cerebellum)

Answer 28

separates the cerebellar hemispheres; intermediate zone lines eitherside

Question 29

what does the intermediate zone (paravermis) and vermis of the cerebellum do for movement

Answer 29

corrects error of smooth, voluntary movements - axial musculature in vermis and limb musculature in paravermis -> there is a homunculus here;
also involved in proprioception and tone

Question 30

what is the function of the cerebrocerebellum

Answer 30

fine tuning of motor info from other brain areas (M1, SMA, PMA, S1, V1 etc.) -> coordinates and regulates movement and is involved in things like writing and playing an intrument

Question 31

what fibers are the main proprioceptors (2)

Answer 31

golgi tendon organ and muscle spindles -> respond to increase in muscle tension

others - cutaneous receptors, joint receptors

Question 32

what is the final output neurone

Answer 32

alpha motor neuron -> final common pathway

Question 33

where in the DH are the interneurons usually found

Answer 33

lamina VII

Question 34

what are renshaw circuits

Answer 34

a recurrent inhibitory network that is associated with 1a motor neurons and play a role in the CPG of locomotion

Question 35

what does the dorsal column enter the spinal chord through

Answer 35

the dorsal root

Question 36

what information is carried in the spinothalamic tract

Answer 36

temperature, pain, crude touch (pressure etc.)

Question 37

dorsal vs ventral premotor streams

Answer 37

dorsal - where
ventral - what

Question 38

what is the mesencephalic locomotion region

Answer 38

a functionally defined area of the midbrain that is associated with the initiation and control of locomotor movements in vertebrate species

Question 39

what neurons are stimulated during anticipation of an object during locomotion

Answer 39

purkinje