Flashcards in motor systems II Deck (22)
How does the motor cortex cause movement?
via the corticospinal (also called the pyramidal tract) or corticobulbar tracts
where does the corticospinal tract cross?
at the lower medulla
does the corticospinal tract activate motoneurons directly?
no; only for fine finger control, otherwise they normally activate interneurons
movements originating from the cortex usually involve what brain structures?
1. premotor cortex
2. supplemental motor cortex
3. basal ganglia
True or false, the net descending influence on reflexes is excitatory
FALSE; the net descending influence on reflexes is inhibitory, often prodding hyper-reflexia (spastic paralysis)
explain the loop involving the cortex and basal ganglia
cortex--> the basal ganglia --> thalamus --> cortex
what is the basal ganglia comprised of?
1. caudate nucleus
3. globus pallidus (internal and external)
4. subthalamic nucleus
5. substantia nigra
why is the basal ganglia important for motor function?
important for the smooth initiation and execution of motor programs
what are 2 examples of basal ganglia dysfunction?
1. parkinson's disease
2. huntington's disease
what causes parkinson's disease?
degeneration of dopamine containing neurons in the substantial nigra
True or False; parkinson's disease is a hypokinetic movement disorder
*slowness in initiating, carrying out and changing motor behaviours (shuffling gait, hard to get going, slow to stop)
degeneration of what brain structure occurs in parkinson's disease?
degeneration of dopamine containing neurons in the substantia nigra (part of the basal ganglia)
what is the cause of huntington's disease?
net reduction in the basal ganglia's inhibition to the thalamus; loss of feedback control for cortically initiated movements
2 movements characteristics of huntington's disease
involuntary movements of the trunk or proximal limbs, often serpentine
fast, often explosive involuntary movements of the limb
true or false; huntington's disease is a hypokinetic disorder
what are the 3 main functional divisions of the cerebellum?
what does dysfunction in the vestibulocerebellum cause?
1. staggering, ataxic gait
2. nystagmus (spontaneous rapid eye movement), vertigo (dizziness)
what does the spinocerebellum do?
functions to compare planned movement to actual movement and create an "error" signal to correct the movement if necessary
what does dysfunction of the spinocerebellum cause?
intention tremor which is a tremor that gets worse as finer finger control is needed