motor systems II

Question 1

How does the motor cortex cause movement?

Answer 1

via the corticospinal (also called the pyramidal tract) or corticobulbar tracts

Question 2

where does the corticospinal tract cross?

Answer 2

at the lower medulla

Question 3

does the corticospinal tract activate motoneurons directly?

Answer 3

no; only for fine finger control, otherwise they normally activate interneurons

Question 4

movements originating from the cortex usually involve what brain structures?

Answer 4

1. premotor cortex
2. supplemental motor cortex
3. basal ganglia
4. cerebellum

Question 5

True or false, the net descending influence on reflexes is excitatory

Answer 5

FALSE; the net descending influence on reflexes is inhibitory, often prodding hyper-reflexia (spastic paralysis)

Question 6

explain the loop involving the cortex and basal ganglia

Answer 6

cortex–> the basal ganglia –> thalamus –> cortex

Question 7

what is the basal ganglia comprised of?

Answer 7

1. caudate nucleus
2. putamen
3. globus pallidus (internal and external)
4. subthalamic nucleus
5. substantia nigra

Question 8

why is the basal ganglia important for motor function?

Answer 8

important for the smooth initiation and execution of motor programs

Question 9

what are 2 examples of basal ganglia dysfunction?

Answer 9

1. parkinson’s disease

2. huntington’s disease

Question 10

what causes parkinson’s disease?

Answer 10

degeneration of dopamine containing neurons in the substantial nigra

Question 11

True or False; parkinson’s disease is a hypokinetic movement disorder

Answer 11

TRUE

*slowness in initiating, carrying out and changing motor behaviours (shuffling gait, hard to get going, slow to stop)

Question 12

degeneration of what brain structure occurs in parkinson’s disease?

Answer 12

degeneration of dopamine containing neurons in the substantia nigra (part of the basal ganglia)

Question 13

what is the cause of huntington’s disease?

Answer 13

net reduction in the basal ganglia’s inhibition to the thalamus; loss of feedback control for cortically initiated movements

Question 14

2 movements characteristics of huntington’s disease

Answer 14

1. chorea

2. ballismus

Question 15

chorea

Answer 15

involuntary movements of the trunk or proximal limbs, often serpentine

Question 16

ballismus

Answer 16

fast, often explosive involuntary movements of the limb

Question 17

true or false; huntington’s disease is a hypokinetic disorder

Answer 17

FALSE; hyperkinetic

Question 18

what are the 3 main functional divisions of the cerebellum?

Answer 18

1. vestibulocerebellum
2. spinocerebellum
3. cerebrocerebellum

Question 19

what does dysfunction in the vestibulocerebellum cause?

Answer 19

1. staggering, ataxic gait

2. nystagmus (spontaneous rapid eye movement), vertigo (dizziness)

Question 20

what does the spinocerebellum do?

Answer 20

functions to compare planned movement to actual movement and create an “error” signal to correct the movement if necessary

Question 21

what does dysfunction of the spinocerebellum cause?

Answer 21

intention tremor which is a tremor that gets worse as finer finger control is needed

Question 22

what does dysfunction in the cerebrocerebellum cause?

Answer 22

difficulty in the smooth planning and execution of movements