Basal Ganglion

Question 1

What is the function of the basal ganglia?

Answer 1

The basal ganglia regulate motor control and movement by modifying signals from the cerebral cortex. Dysfunction leads to dyskinesias (involuntary purposeless movements)

Question 2

What are the major components of the basal ganglia?

Answer 2

1. Caudate nucleus
   
   2. Putamen
   3. Globus pallidus (internal and external)
   4. Subthalamic nucleus
   5. Substantia nigra

Question 3

What is the structure and location of the caudate nucleus?

Answer 3

haped mass of grey matter, consisting of a head, body, and thin tail. It lies inferior to the anterior horn of the lateral ventricle.

Question 4

What is the functional role of the caudate nucleus?

Answer 4

It receives input mainly from the cortex and subcortical areas and secretes GABA and neuropeptides (substance P and enkephalin) to inhibit target organs.

Question 5

What is the function of the putamen?

Answer 5

It works with the caudate nucleus to form the corpus striatum and is involved in motor control by modulating inhibitory and excitatory signals

Question 6

What are the two segments of the globus pallidus?

Answer 6

Internal segment (GPi): The main output nucleus sending inhibitory GABA projections to the thalamus.
* External segment (GPe): Works with the subthalamic nucleus in the indirect pathway.

Question 7

What are the two parts of the substantia nigra and their neurotransmitters?

Answer 7

• Pars compacta: Secretes dopamine, which modulates striatal activity.
  
  • Pars reticulata: Secretes GABA and projects to the thalamus.

Question 8

Where is the subthalamic nucleus located and what is its role?

Answer 8

It is located in the rostral midbrain within the cerebral peduncle at the level of the superior colliculus. It provides an excitatory glutamatergic output to the globus pallidus and substantia nigra.

Question 9

What are the afferent (input) connections of the corpus striatum?

Answer 9

1. Cortex
   
   2. Thalamus
   3. Substantia nigra (dopamine input)

Question 10

What is the efferent (output) connection of the corpus striatum?

Answer 10

It projects to the GPi, which then sends inhibitory signals to the thalamus.

Question 11

What are the three major neuronal circuits of the basal ganglia?

Answer 11

1. Direct pathway – facilitates movement
   
   2. Indirect pathway – inhibits movement
   3. Hyperdirect pathway – modulates rapid response

Question 12

What is the substantia nigra (SN)?

Answer 12

A large motor neuron in the midbrain

The substantia nigra is involved in the regulation of movement and contains two parts: pars reticularis and pars compacta.

Question 13

What are the two parts of the substantia nigra?

Answer 13

• Pars reticularis: GABA (-) to thalamus
• Pars compacta: dopaminergic (NT D1, D2)

The pars reticularis primarily sends inhibitory signals while the pars compacta is involved in dopamine production.

Question 14

What type of neurotransmitter does the pars compacta of the substantia nigra secrete?

Answer 14

Dopamine

Dopamine is crucial for facilitating movement and is associated with reward pathways.

Question 15

What are the primary afferent connections to the striatum?

Answer 15

• Corticostriate fibers (from cortical cortex, glutamatergic)
• Thalamostriate fibers (intralaminar nuclei)
• Nigrastriate (from pars compacta, dopaminergic)
• Noradrenergic fibers (from locus coeruleus)
• Serotoninergic fibers (from raphe)

These connections provide input from various brain regions to the striatum, influencing movement and behavior.

Question 16

What are the efferent connections from the basal ganglia?

Answer 16

• Fasciculus lenticularis (from GPi)
• Ansa lenticularis (from GPi and GPe)
• Thalamic fasciculus (terminates in VA, VL, and centromedial nuclei of thalamus)

These pathways transmit output signals from the basal ganglia to various thalamic nuclei, influencing motor control.

Question 17

What types of neurons are found in the striatum?

Answer 17

• Small spiny neurons
• Medium spiny neurons (most)
• Large spiny neurons
• Aspiny neurons (10%)

Medium spiny neurons are the predominant type and play a key role in the direct and indirect pathways of motor control.

Question 18

What is the function of the direct pathway in the basal ganglia?

Answer 18

Excitatory to the motor cortex

This pathway facilitates movement by enhancing motor signals to the cortex.

Question 19

What is the function of the indirect pathway in the basal ganglia?

Answer 19

Inhibitory to the motor cortex

This pathway suppresses unwanted movements by inhibiting motor signals.

Question 20

What is the hyperdirect pathway in the basal ganglia?

Answer 20

A pathway that provides rapid inhibition to the motor cortex

This pathway allows for quick responses to stimuli, influencing immediate motor control.

Question 21

True or False: The substantia nigra is part of the midbrain.

Answer 21

True

The substantia nigra is located in the midbrain and is crucial for movement regulation.

Question 22

Fill in the blank: The striatum receives afferent fibers from the _______.

Answer 22

Cortex

The cortex sends glutamatergic fibers to the striatum, which are integral for motor control.

Question 25

What is the primary function of the Direct Pathway in the basal ganglia?

Answer 25

Increase thalamic function ## Footnote The direct pathway facilitates movement by promoting thalamic activity.

Question 26

What neurotransmitter is primarily involved in the Direct Pathway?

Answer 26

Glutamate ## Footnote Cortical inputs excite the striatum via glutamate.

Question 27

What is the role of GABA in the Direct Pathway?

Answer 27

Striatum releases GABA to GPi ## Footnote This action decreases the activity of GPi, leading to less inhibition of the thalamus.

Question 28

What is the effect of increased glutamate on the motor cortex?

Answer 28

More excitation, promote movement ## Footnote Increased glutamate levels lead to enhanced motor activity.

Question 29

What are the negative signs associated with basal ganglia disorders?

Answer 29

* Difficulty in movement (akinesia) * Bradykinesia ## Footnote Negative signs indicate a patient wants to move but cannot.

Question 30

What are the positive signs associated with basal ganglia disorders?

Answer 30

* Hypertonicity * Rigidity * Abnormal movements (dyskinesia) * Tremors ## Footnote Positive signs reflect unwanted movements and muscle tone changes.

Question 31

What characterizes bradykinesia?

Answer 31

Reduction in velocity and amplitude of movement ## Footnote Bradykinesia is a common symptom in Parkinson's disease.

Question 32

What is the function of the Indirect Pathway in the basal ganglia?

Answer 32

Decrease thalamic function ## Footnote The indirect pathway acts as a brake on movement.

Question 33

How does the Indirect Pathway affect the output from the thalamus?

Answer 33

Inhibits the output ## Footnote This leads to less excitation of the motor cortex.

Question 34

What is the impact of the Indirect Pathway on the motor cortex?

Answer 34

Decreased movement ## Footnote The indirect pathway results in less motor output.

Question 35

What disease is characterized by chorea and issues with the striatum?

Answer 35

Huntington's disease ## Footnote This condition results in impaired processing of cortical input.

Question 36

What is a hallmark symptom of Parkinson's disease?

Answer 36

Pill-rolling motion in fingers ## Footnote This symptom is a characteristic feature of the disease.

Question 37

What role does the substantia nigra play in the basal ganglia pathways?

Answer 37

Releases dopamine ## Footnote Dopamine is crucial for modulating the pathways' activity.

Question 38

Fill in the blank: The striatum is composed of the ______ and ______.

Answer 38

caudate + putamen ## Footnote These structures are integral components of the basal ganglia.

Question 39

What condition is associated with hemiballismus?

Answer 39

Hemiballismus ## Footnote This condition involves involuntary jerky movements.