Basal Nuclei

Question 1

what does baseline activity allow for?

Answer 1

• common throughout the nervous system, allows for increase and decrease in activity (activity never completely turned off)
• allows for fine tuning
• sensitivity

Question 2

what does baseline activity allow for?

Answer 2

• common throughout the nervous system, allows for increase and decrease in activity (activity never completely turned off)
• allows for fine tuning
• sensitivity

Question 3

basal ganglia

Answer 3

• directly effect UMN cortex through modulation.
• determine appropriateness of actions, emotions, cognition: decide what behavior is most likely to be “Correct”
• “basal nuclei” is more appropriate name, they are subcortical grey matter

Question 4

basal ganglia

Answer 4

• directly effect UMN cortex through modulation.
• determine appropriateness of actions, emotions, etc.
• “basal nuclei” is more appropriate name, they are subcortical grey matter

Question 5

what forms striatum of basal nuclei?

Answer 5

caudate nucleus and putamen

• note: caudate nucleus forms lateral wall of ventricle
• called “striatum” because they have myelinated axons passing through causing them to look striated.

Question 6

what forms lentiform nucleus?

Answer 6

putamen
+
globus pallidus (internal and external)

(have a lens like appearance together)

Question 7

what is globus pallidus composed of?

Answer 7

GPe (external) or “lateral” segment

GPi (internal) or “medial” segment

• globus pallidus lies just medial to putamen

Question 8

substantia nigra involvement in basal ganglia?

Answer 8

pars compacta (SNc): releases dopamine

pars reticulata (SNr)

Question 9

substantia nigra involvement in basal ganglia?

Answer 9

pars compacta (SNc): releases dopamine

pars reticulata (SNr)

Question 10

Disinhibtion

Answer 10

= removal of an inhibitory effect by a stimulus

• “inhibition of an inhibition”
• inhibitory = gabaminergic
• disinhibitory = glutamatergic

Question 11

basal ganglia

Answer 11

• directly effect UMN cortex through modulation.
• determine appropriateness of actions, emotions, etc.
• “basal nuclei” is more appropriate name, they are subcortical grey matter

Question 12

what forms striatum of basal nuclei?

Answer 12

caudate nucleus and putamen

• note: caudate nucleus forms lateral wall of ventricle
• called “striatum” because they have myelinated axons passing through causing them to look striated.

Question 13

what forms lentiform nucleus?

Answer 13

putamen
+
globus pallidus (internal and external)

(have a lens like appearance together)

Question 14

what is globus pallidus composed of?

Answer 14

GPe (external) or “lateral” segment

GPi (internal) or “medial” segment

• globus pallidus lies just medial to putamen

Question 15

what portions of thalamus are involved in the in basal ganglia?

Answer 15

subthalamic nucleus

thalamus

Question 16

substantia nigra involvement in basal ganglia?

Answer 16

pars compacta (SNc): releases dopamine

pars reticulata (SNr)

Question 17

what are the two paired circuits of the basal nuclei?

Answer 17

1. Direct pathway: “yes” loop
2. indirectly pathway: “no”/don’t loop
   - determine Motor, cognition and affect
   - there are two paired circuits in each hemisphere that run in a parallel manner

Question 18

where does output/input from basal nuclei come from? how do they influence the cortex?

Answer 18

input: from striatum (pyramidal cells and motor cx always project in through striatum)
output: globus pallidus internus and substantia nigra

final projection is into the thalamus. the thalamus ultimately influences the cortex (though this is technically not part of the basal nuclei )

Question 19

draw out direct and indirect pathways.

Answer 19

do it now.

and memorize it.

Question 20

direct loop: actions of ACH and dopamine

Answer 20

ACH: cholinergic neurons of striatum are inhibitory. ACH is released and ultimately results in decreased cortical activity of direct loop.

Dopa: released from SNc and binds D1 receptors: results in depolarization: facilitates cx through increasing thalamic activity (thalamus is disinhibited)

Question 21

indirect loop: actions of ACH and dopamine

Answer 21

ACH: cholinergic neurons of striatum are excitatory and decreases cortical activity of indirect loop

Dopa: released from SNc binds to D2: results in hyperpolarization: facilitates cx through increasing thalamic activity (subthalamic is disinhibited)

Question 22

what is role of substantia nigra compacta?

Answer 22

releases dopamine

• Dopa depolarizes (excitatory) to D1 receptors of direct loop, results in facilitating cortex
• dopa hyperpolarizes (inhibitory) to D2 receptors of indirect loop, thus facilitating cortex
• this is what is damaged in Parkinson’s disease* thus increased cortical activity is lost with parkinson’s disease

Question 23

what does ACA supply to basal nuclei?

Answer 23

head of caudate

nucleus accumbens

Question 24

what does branches of MCA (lenticulostriate) supply of basal nuclei?

Answer 24

Lentiform (putamen and GP)

majority of caudate***

Question 25

what does branches of PCA supply?

Answer 25

- substantia nigra - subthalamic nucleus *** this is the most common place for stroke lesions, will produce hemiballismus symptoms = decrease in activity of the subthalamic nucleus of the basal ganglia, resulting in the appearance of flailing, ballistic, undesired movements of the limbs.

Question 26

what do pathologies of the basal nuclei usually present through?

Answer 26

- movement disorders - not directly affecting strength, coordination or sensation - VOLUNTARY movmt systems are affected - will see abnormalities of tone (increased or decreased) depending on lesion - akinetic or hyperkinetic depending on lesion

Question 27

negative vs. positive signs

Answer 27

``` neg = reduced mvmt pos = increased/inappropriate mvmt ```

Question 28

four different types of kinesias...

Answer 28

``` akinesia = no mvmt hypokinesia = reduced mvmt bradykinesia = slow mvmt dyskinesia = inappropriate/incorrect mvmt ```

Question 29

tremor

Answer 29

- oscillatory mvmt (4-6 Hz) | - greatest at rest, they are decreased with voluntary mvmt

Question 30

athetosis

Answer 30

slow writhing mvmt

Question 31

chorea

Answer 31

abrupt, rapid, jerking dance like (often distal limbs and orofacial mm)

Question 32

choreoathetosis

Answer 32

mixture of slow writhing mvmt and abrubt jerking.

Question 33

ballism

Answer 33

violent flinging | - usually unilateral = hemiballismus

Question 34

Parkinson's disease cause

Answer 34

- late onset disease (<50 y/o) - unknown cause - results in degeneration of SNc and loss of Dopa neurons - substantia nigra looks severely lesioned - results in decreased activity of cortical motor neurons - cx is inhibited

Question 35

Parkinson's disease symtpoms: negatives and positives?

Answer 35

Negative signs: - hypokinesia/bradykinesia - Gait is small, shuffling steps - facial masking - loss of postural reflexes (flexed stooped posture) - late cognitive defects - difficulty initiating gait Positive signs: - Tremor that occurs at rest (pill rolling)

Question 36

Therapy for Parkinson's disease

Answer 36

- Replace missing L-dopa (effectiveness decreases over time) - replace missing cells of SNc via stem cell transplant (will eventually die just as predecessors did) - reduce the activity of indirect loop

Question 37

huntington's disease cause?

Answer 37

- earlier onset: age 30-40y/o - due to multiple CAG repeats on chromosome 4 "huntington protein" - autosomal dominante - results in degeneration of striatum (caudate) of indirect loop

Question 38

symptoms of huntington's disease

Answer 38

positive changes: - hyperkenisias - choreoathetosis "huntingtono's chorea" negative symptoms: - dementia and cognitive changes (caudate is important part of "cognitive loops") - psychoses (hallucinations and paranoia) - very little treatment. developes earlier than parkinson's disease