Chapter 14: Brain Control Of Movement

Question 1

What are the six steps of the corticospinal tract?

Answer 1

1) cortical spinal tract begins at spinal cord
2) pyramidal decussation
3) goes through the medullary pyramids in the medulla
4) goes through base of cerebral peduncle in the midbrain
5) goes through thalamus and internal capsule
6) reaches motor cortex

Question 2

What are two effects of corticospinal lesions?

Answer 2

• difficulty moving distal limbs - may recover over time

- loss of ability to make independent finger movements - does not recover

Question 3

Explain what each ventromedial pathway regulates

Answer 3

Vestibulospinal tract: balance

Tectospinal tract and tectbulbar tract: orienting reflexes

Pontine and medullary reticulospinal tracts: locomotion and posture

Question 4

Explain the 2 steps of the vestibulospinal tract?

Answer 4

Starts in spinal cord

Reaches vestibular nucleus in medulla

Question 5

Explain the tectospinal tract

Answer 5

Initiates in Spinal cord
Goes through medulla where it decussates
Terminates in superior colliculus

Question 6

Explain the medullary reticulospinal tract

Answer 6

Spinal cord initiation

Terminates in medullary reticular formation

Question 7

Explain the pontine reticulospinal tract

Answer 7

Initiates in spinal cord
Goes through medulla
Terminates in pontine reticular formation

Question 8

Where do lateral pathways synapse

Answer 8

Synapse on motor neurons innervating distal pathways and flexors

Question 9

Where do ventromedial pathways synapse

Answer 9

Synapse on motor neurons innervating axial muscles and extensors

Question 10

What is the area for the primary motor cortex?

Answer 10

Area 4

Question 11

Where does the corticospinal tract originate from?

Answer 11

Layer 5 Betz cells in area 4 of M1

Question 12

In relation with voluntary movement, when does activity happen in M1 neurons?

Answer 12

Before and after

Question 13

Explain direction vectors

Answer 13

Certain Cells fire most to leftward (example) direction vector points.

Question 14

What does a higher firing rate entail (direction vectors)

Answer 14

Higher firing rate=more force

Question 15

What can you say about direction vectors

Answer 15

Points in the preferred direction for the neuron, but it’s length depends on the firing rate over a range of direction

Question 16

What is a population vector?

Answer 16

Vector sum

Question 17

What does the primary motor area do? What area?

Answer 17

Initiation of complex voluntary movement

Question 18

What do the supplementary motor And premotor areas do? What area?

Answer 18

Motor planning

Area 6

Question 19

What are the 4 function of the prefrontal association cortex?

Answer 19

• executive function
• abstract thought
• decision making
• anticipating consequences of action

Question 20

What does the P-T-O association cortex do?

Answer 20

• analysis of sensory inputs (vision, somatosensory, auditory)
• constructs representation of our sensory world
• proprioceptors - current position of our body in space

Question 21

What does the basal ganglia do?

Answer 21

Selects and initiates willed movements

Question 22

What are the 4 sections of the basal ganglia?

Answer 22

Striatum: caudate nucleus/putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra

Question 23

Direct Pathway

Answer 23

EXCITATORY LOOP

Cortex excites striatum
striatum excites globus pallidus
globus pallidus inhibits thalamus
Thalamus excited cortex

Question 24

Indirect Pathway

Answer 24

Suppresses unwanted movement

Cortex excites striatum
Striatum inhibits globus pallidus external
Globus pallidus external inhibits subthalamic nuclei
Subthalamic nuclei excites internal globus pallidus
Internal globus pallidus inhibits thalamus

Question 25

Explain the body movement loop of the basal ganglia

Answer 25

Cortex transiently excited putamen (striatum) The putamen transiently inhibits the globus pallidus The globus pallidus inhibits the VL/VA thalamus VL/VA is released from inhibition and excites the cortex

Question 26

What leads to hypokinesis? Cite an example

Answer 26

An increase in GP output. Eg: Parkinson

Question 27

What leads to hyperkinesis? Cite example

Answer 27

Over excitation of thalamus, Huntington's, hemibalismus

Question 28

Explain how the frontal/parietal cortex is linked with the cerebellum cortex

Answer 28

Frontal/parietal—>red nucleus—>inferior olive—>goes through inferior cerebellar peduncle—>cerebellar cortex Or Frontal/parietal cortex—>pontine nuclei—>goes through middle cerebellar peduncle—>cerebellar cortex

Question 29

Which movement does the motor cortex dictate?

Answer 29

Intended movement

Question 30

Which movement does the inferior cerebellar peduncle dictate?

Answer 30

Actual movement

Question 31

Where does the cerebellar cortex receive inputs from?

Answer 31

Inferior olive, spinal cord, vestibular nuclei

Question 32

Huntington's Disease

Answer 32

Hyperkinesia | Loss of neurons in striatum and globus pallidus, not enough inhibition to thalamus, and thus over excitation

Question 33

Parkinson's Disease

Answer 33

Hypokinesia Damage to dopamine cells in substantial Niagara More inhibition of thalamus, feedback loop to cortex inhibited Deep brain stimulation can be cure

Question 34

Hemiballismus

Answer 34

Hyperkinesia | Due to stroke, subthalamic nuclei is damaged, inhibition of globus pallidus to cortex not enough, over excitation

Question 35

Cells in Cerebellum

Answer 35

``` granule cells • tiny excitatory neurons • # of granule cells in cerebellum is almost = to the total # of neurons in the CNS! • Purkinje cells • largest neurons in the cerebellum • receives excitatory input from granule cells in the molecular layer • sends inhibitory axons to deep cerebellar nuclei ```

Question 36

Cerebellum Function and Dysfunctions

Answer 36

``` Function: coordinate a detailed sequence of muscle contractions • Cerebellar lesions: • Ataxia: uncoordinated and inaccurate movements • Dyssynergia: decomposition of synergistic multi-joint movements • Dysmetria: overshoot or undershoot target • dyssynergia and dysmetria are characteristic of alcohol intoxication ```

Question 37

Pontine nuclei

Answer 37

–Axons from layer V pyramidal cells in the sensorimotor cortex send massive projections to pons

Question 38

Corticopontocerebellar projection

Answer 38

``` – 20x larger than pyramidal tract –Lateral cerebellum projects back to motor cortex via VLc • Lesions suggest that the cerebellum is involved in the proper execution of planned, voluntary, multi-joint movement ```

Question 39

Cerebellum and Learning

Answer 39

Site of motor learning • Instructs the primary motor cortex (direction, timing, and force of movement) • Uses past experience to make predictions about outcome • Skill mastery comes with practice • Movements become smooth