Motor Systems

Question 1

Hierarchical Control of Movement

Answer 1

Neocortex (conscious), brainstem and spinal cord (automatic)
Normally functions as a whole

Hughlings-Jackson
(19th Century)
Conceived of nervous system as organized in successive layers, with higher levels controlling complex behavior by acting through lower levels

Question 2

1930’s Concept and Karl Lashley’s concept

Answer 2

1930’s concept:
Action->Feedback (action successful)->Action1950’s

Karl Lashley - Movements for skilled actions are performed quickly to rely on feedback. Complex behaviours require selecting and executing multiple movement sequences. As one sequence is executed, the next sequence is being prepared.

Question 3

The Forebrain and Initiation of Movement

Answer 3

Frontal Lobes
Prefrontal Cortex: Planning of movements, specifying the goal (e.g. deciding to play with iPhone)
Premotor Cortex: Organizes motor sequences (e.g. select movements appropriate to the context of the action)
Primary Motor Cortex: Produces specific, skilled movements

Question 4

Measuring cerebral blood flow while performing various motor tasks

Answer 4

Blood flow increases in the hand area of the primary somatosensory and primary motor cortex when finger is used to push a button. When performing a sequence of movements blood flow increases in the premotor cortex. When using a finger to find the route out of the maze blood flow increases in the prefrontal, temporal and porietal lobe.

Question 5

Corticospinal Tracts

Answer 5

Bundle of nerve fibers directly connecting the cerebral cortex to the spinal cord.
Lateral Corticospinal Tract
Branches at the brainstem level, crossing over to the opposite side of the brain and spinal cord
Moves the digits and limbs on the opposite side of the body
Ventral Corticospinal Tract
Remains on the same side of the brain and spinal cord
Moves the muscles of the midline body (trunk) on the same side of the body

Question 6

Neurons

Answer 6

Interneurons project to motor neurons

Motor neurons project to muscles of the body
Laterally located motor neurons project to the muscles that control the fingers and hands
Intermediately located motor neurons project to muscles that control the arms and shoulders
The most medially located motor neurons project to muscles that control the trunk

Question 7

The Basal Ganglia and Movement Force

Answer 7

Collection of subcortical nuclei within the forebrain. Receives input from
All areas of the neocortex (e.g. motor cortex) and limbic cortex (e.g. amygdala, hippocampus)
Project back to the motor cortex
Allow us to adjust the force of our movements

Question 8

Volume Hypothesis

Answer 8

The internal globus pallidus acts like a volume dial and projects to the thalamus, which projects to the motor cortex
Two pathways within the basal ganglia
Direct
Inhibitory effect on GPi: Too much activity leads to overactivity in the thalamus and amplified force of movement
Indirect
Excitatory effect on GPi: Too much activity leads to underactivity in the thalamus and reduced force of movement

Question 9

Hyperkinetic Symptom

Answer 9

Symptom of brain damage that results in excessive involuntary movements, as seen in Huntington’s Chorea or hemiballism

Question 10

Huntington’s Chorea

Answer 10

Genetic disorder, affects muscle coordination

• Symptoms: excessive spontaneous movements, irregularly timed, randomly distributed, and abrupt in character
• Atrophy of caudate nucleus and putamen (degeneration of indirect pathway neurons, direct pathway spared)

Question 11

Hemiballism

Answer 11

Caused by stroke to the subthalamic nucleus

• Results in involuntary, fast, movements
• Treatment: clozapine (dopamine blocker)

Question 12

Parkinson’s disease (PD)

Answer 12

• Slowly progressive disorder that affects movement, muscle control,
and balance.

• Symptoms: slowness of movement, resting tremor, stiffness of muscles, ‘gait’: small shuffling of steps
• Loss of substantia nigra that sends dopamine projections to putamen that controls movement and coordination. (can be chemically induced by the toxin ‘MPTP’

Question 13

The Cerebellum and Movement Skill

Answer 13

Flocculus
Small but dense lobe involved in eye movements and balance
Inputs from vestibular system

Two hemispheres
- Homuncular organization
- Lateral parts
Controls movement of limbs, hands, feet, and digits
Medial parts
Controls movement of face and midline of body