19 Basal Ganglia

Question 1

What are general functions of the basal ganglia?

Answer 1

ipsilateral motor cortices for proper movement, tone and posture, play a poorly understood role in cognitive and emotional functions

Question 2

What are the two portions of the striatum?

Answer 2

caudate and putamen (and nucleus accumbens)

Question 3

What are the two parts of the globus pallidus called?

Answer 3

internal and external

Question 4

Name the 4 major parts of the basal ganglia.

Answer 4

stratum, globus pallidus, sub thalamic nucleus and substantial nigra (midbrain)

Question 5

Describe the input to the basal ganglia.

Answer 5

external excitatory projections mostly from the cerebral cortex (areas of planning and execution of movements) to the striatum

Question 6

What output pathways project from the basal ganglia?

Answer 6

from the internal globus pallidus (to reticular substantia nigra project) to the ventral anterior and ventral lateral nuclei

Question 7

What are the effects of the direct v. the indirect pathways in motor activity excited by thalamic activity

Answer 7

direct pathway increases, indirect pathway decreases

Question 8

Delineate the steps in the direct pathway.

Answer 8

cortical cells synapse on stratum which projects to the GPe and the reticular substantial nigra, this projection causes decreased inhibition of the thalamus and more motor cortical activity

Question 9

Delineate the steps in the indirect pathway.

Answer 9

cortical cells synapse on the stratum and inhibits the external globus, which decreases the inhibition of the subthalamic nucleus. Subthalamic nucleus then increases its excitation of the internal globus pallidus and reticular substantial nigra. The substantia nigra and internal globus pallidus increase their inhibition of the thalamus and decreasing excitation of the motor cortex

Question 10

What’s another way to refer to dyskinesias?

Answer 10

previously they were referred to as extrapyramidal signs (which is not entirely accurate)

Question 11

What are the cause and associated symptoms of Ballism?

Answer 11

caused by a lesion on the subthalamic nucleus, which would normally increase inhibition of the thalamus is damaged leading to involuntary, fast, large proximal limb movements

Question 12

Define tremor.

Answer 12

an involuntary alternating movement that can be described with rhythmicity, amplitude, frequency and affected body parts; can include rest tremors and action tremors (movement or posture)

Question 13

What is dystonia?

Answer 13

involuntary sustained contraction of one or more muscles causing abnormal movements or postures

Question 14

What is chorea?

Answer 14

involuntary, fast, irregular mostly distal limb movements that resemble dancing

Question 15

What is athetosis?

Answer 15

involuntary, slower, writhing, mostly of the distal limb movements that resemble the movement of snakes

Question 16

What is myoclonus?

Answer 16

involuntary movements that are small and rapid (a jerk), usually of bilateral proximal limbs and trunk (a jerk you might experience as you fall asleep)

Question 17

What is a tic?

Answer 17

semi involuntary movement or vocalization that relive a progressively uncomfortable sensation and which may be briefly suppressed with concentration

Question 18

What is the function of the compact substantia nigra?

Answer 18

it receives inputs from many brain areas and projects dopamine to ipsilateral striatum via the nigrostriatal tract to either excitatory or inhibitory receptors (the end result is to increase the activity of the direct pathway and decreasing the activity of the indirect pathway)

Question 19

Parkinisonism is dysfunction of what?

Answer 19

the nigrostriatal tract which causes bradykinesia, rigidity (velocity- independent hypertonia), and rest tremor

Question 20

What is the effect of acetylcholine on the basal ganglia system?

Answer 20

acts through neurons in and out of the basal ganglia and mostly favors indirect pathway (decrease motor activity overall)

Question 21

Name some non-motor functions of the basal ganglia.

Answer 21

plays a role in cognition, emotion and in particular reward centers (accumbens nucleus)