Basal Nuclei

Question 1

what are the basal nuclei

Answer 1

a collection of deep nuclei found within the cerebrum that contribute to the modulation of ALL OUTPUT that leaves the cortex

Question 2

striatum

Answer 2

caudate + putamen

Question 3

lenticular (lentiform) nucleus

Answer 3

putamen + globus pallidus

Question 4

5 basal nuclei structures

Answer 4

1) substantia nigra (2 components: pars compacta and para reticulata)
2) subthalamic nucleus
3) putamen
4) caudate nucleus
5) globus pallidus (2 components: GP externus and GP internus)

Question 5

general function of the striatum

Answer 5

receives all of the inputs coming in to basal nuclei

Question 6

general roles of the basal nuclei

Answer 6

-general motor commands*
-eye movements
-cognitive functions
-emotional functions

Question 7

direct pathway of basal nuclei - overall function

Answer 7

EXCITATION of the thalamus, allowing for activation of cortex and thus stimulation of movement

Question 8

indirect pathway of basal nuclei - overall function

Answer 8

INHIBITION of the thalamus, leading to inhibition of movement

Question 9

what structure separates the caudate from the putamen

Answer 9

the internal capsule

Question 10

what structure separates the two halves of the thalamus

Answer 10

third ventricle

Question 11

where do all inputs to the basal nuclei arrive

Answer 11

striatum (caudate & putamen)

Question 12

where do all outputs from the basal nuclei arise from

Answer 12

globus pallidus internus and pars reticulata of substantia nigra

Question 13

direct pathway - steps

Answer 13

1) cortex sends glutamate to the striatum
2) striatum sends GABA to GPi and SN pars reticulata, inhibiting them
3) GPi and pars reticulata STOP INHIBITING the thalamus
4) thalamus is free to activate cortex and initiate movement

Question 14

indirect pathway - steps

Answer 14

1) striatum sends GABA to the globus pallidus EXTERNUS, inhibiting it
2) GPe STOPS INHIBITING the subthalamic nucleus
3) subthalamic nucleus STIMULATES the globus pallidus INTERNUS, causing the GPi to produce MORE GABA
4) GPi producing more GABA further INHIBITS the thalamus, preventing it from activating cortex

Question 15

cause of Parkinson’s disease

Answer 15

dopaminergic neurons that are projecting to the striatum (from pars compacta of substantia nigra) die

Question 16

cause of hemiballism

Answer 16

damage to the subthalamic nucleus

Question 17

dyskinesia

Answer 17

abnormal movements
*result from unilateral lesions of basal nuclei, causing contralateral effects

Question 18

bradykinesia

Answer 18

slow movement

Question 19

hypokinesia

Answer 19

decreased amount of movement

Question 20

akinesia

Answer 20

absence of movement

Question 21

hyperkinesia

Answer 21

increased movements

Question 22

rigidity

Answer 22

resistive tone initially increases then decreases
*increased limb resistance to passive movement
examples = clasp-knife, cogwheel, lead pipe (characteristic of Parkinson’s)

Question 23

dystonia

Answer 23

abnormal or distorted positions
(torticollis)

Question 24

athetosis

Answer 24

writhing twisting movements

Question 25

chorea

Answer 25

dance-like involuntary movements (Huntington’s)

Question 26

ballismus

Answer 26

large amplitude flinging of limbs (hemiballismus)

Question 27

lead-pipe rigidity

Answer 27

constant resistance throughout bending
*characteristic of Parkinson’s

Question 28

cogwheel rigidity

Answer 28

*tremor on top of rigidity
*with Parkinson’s: ratchet-like interruptions in tone throughout limb bending