Subcortical structures

Question 1

brain stem

Answer 1

“motor function”

• sensory pathways from body -> brainstem -> cerebral cortex
• some facial and neck muscles connect directly to brain stem

Question 2

cerebromedullospinal disconnection: “locked-in” syndrome

Answer 2

• stroke to their brain stem
• result - no descending signals from brain and could have no ascending signals from body (paralyzed)
• motor imagery, thinking about doing an activity excites neurons and diagnostic of locked-in syndrome

Question 3

basal ganglia: direct pathway

Answer 3

• allows production of movement
• glutamate neurotransmitter excites, GABA inhibits

Structures:

• striatum
• globus pallidus (internal and external)
• substantia nigra (reticulata and compacta)
• subthalamic nucleus (STN)

Direct Pathway

nigrostriatal pathway: dopamine release pathway that facilitates activity in the direct pathway

cortex excites striatium

striatum inhibits substantia nigra reticulata + globus pallidus internal

substantia nigra reticulata and globus pallidus internal inhibit thalamas

thalamus is dis-inhibited and excites cortex for movement

Question 4

basal ganglia: indirect pathway

Answer 4

cortex -> no need for movement

cortex excites striatum to inhibit globus pallidus external

globus pallidus inhibits subthalamic nucleus

subthalamus nucleus is then dis-inhibited and excites the substantia nigra reticulata and globus pallidus internal

substantia nigra reticulata and globus pallidus internal inhibit the thalamus to prevent movement

Question 5

cerebellum

Answer 5

important role in postural control, motor movement, movement timing and motor learning

Question 6

cerebellar atrophy and dysmetria

Answer 6

Individual with cerebellar atrophy with ataxia gait (poor walking straight), very poor coordination and muscle control

Individual with dysmetria overshooting when doing nose to finger movement

Hypometric: undershoot movements

Hypermetric: overshoot movements

Question 7

individuals with cerebellum lesion vs healthy

Answer 7

motor learning

• Drawing a mirrored picture
• Healthy individual draws poorly at first 10 tries, but 41-50 tries the person draws better
• Individual with cerebellum lesion draws same at 1-10 and 41-50 tries, demonstrates importance of cerebellum and motor learning.

movement timing

• Individuals throw tennis balls at wall with bullseye
• Healthy controls had consistent throws
• Cerebellar patients were not accurate and inconsistent since they couldn’t release the ball properly at the right time

Question 8

Hemmorrhagic stroke and Ischemic stroke

Answer 8

Hemmorrhagic stroke

• an artery bursts in the brain
• artery in brain might have a bulge and leak
• blood is very toxic to neurons and will die

Ischemic stroke

• stroke from a blockage of arteries to the brain, close off blood flow to the brain

Question 9

Magnetic Resonance Imaging (MRI)

Answer 9

T1 - fat appears bright (myelin)

T2 - water appears bright, representing cerebral spinal fluid, after a stroke the neurons and glial cells in the area die and gets filled with cerebral spinal fluid