Week 11 - Basal Ganglia and Disorders of the CNS

Question 1

What is the corticobulbar tract?

Answer 1

Connects cerebral cortex with cranial nerve nuclei in brainstem involved with motor function

Question 2

What can the corticobulbar tract do?

Answer 2

It can compensate for damage on one side of the brain using the other side as most of the nuclei receive ipsilateral and contralateral input.

However it cannot compensate for:
- Lower half of the face (lower side only has contralateral innervation // no ipsilateral)
- Aspects of tongue movement (bc it has significant innervation from contralateral side and not much from ipsilateral so damage to one side affects the other a lot)

Question 3

What are the 3 different types of white matter fiber projections?

Answer 3

Association, Projection & Commissural

Question 4

What does Commissural fibres mean? and examples

Answer 4

fibres that travel from one hemisphere to the other

-> Corpus callosum, Anterior commissure & Posterior commissure

Question 5

What does Association fibres mean? and examples

Answer 5

fibres that travel within one hemisphere

-> Superior longitudinal fasciculus, Arcuate fasciculus, Uncinate fasciculus, Inferior longitudinal fibers , short fibers

Question 6

What does Projection fibres mean?

Answer 6

fibers that take info from the cortex past the thalamus to the brain stem and spinal cord

Question 7

Internal capsule visualised

Answer 7

Question 8

What are the Basal Ganglia?

Answer 8

Series of nuclei located in the clusters deep in the brain

Question 9

What are the relationship pathways between the several parts of the brain?

Answer 9

Question 10

What are the two parts of the substantia nigra? and which is the important one?

Answer 10

Compacter part and reticular part

Reticular part = output source of basal nuclei and project to the thalamus and brain stem

Compacter part = important in Parkinson’s

Question 11

How does the direct and indirect pathway of the basal ganglia act?

Answer 11

Direct = acts through basal nuclei to enhance cortical activity via the thalamus

Indirect = acts to inhibit it

Question 12

Process of Direct basal ganglia pathway?

Answer 12

Direct:
Cortex -> Excitatory inputs to inhibtory neurons in the Putamen -> Increased inhibition (less firing) to the inhibitory neuron in the globus pallidus -> Increased firing of neuron in globus pallidus to the thalamus -> Cortex

Direct = right on diagram

Question 13

Process of Indirect Basal Ganglia pathway?

Answer 13

Indirect:
Cortex -> Excitatory inputs to inhibitory neuron in Putamen -> Increased inhibition (less firing) to the inhibitory neuron in the excitatory neuron in subthalamic nucleus -> increased firing of neuron in subthalamic nucleus to the inhibitory neuron in globus pallidus -> increased inhibition (less firing) to thalamus -> cortex

Indirect = left on diagram

Question 14

Process of Modulatory Basal Ganglia pathway?

Answer 14

• Compacter part of Subtantia nigra releases dopamine
• Has an inhibitory effect on the indirect pathway (blocks indirect) -> increase thalamic output
• Stimulates the direct pathway -> increases thalamic output

Question 15

What happens to substantia nigra in parkinson’s disease?

Answer 15

Lose substantia nigra neurons so no modulatory pathway -> less thalamic output

Question 16

Parkinson’s Disease symptoms

Answer 16

Bradykinesia
Rigidity
Tremor
Gait and Balance abnormalities

Question 17

How do you test for Parkinson’s symptoms?

Answer 17

Bradykinesia -> rapid alternating movements
Rigidity -> passive manipulation of limbs
Tremor -> resting, postural and kinetic
Gait -> less step length, loss of balance, etc

Question 18

What happens to basal ganglia in Huntington’s disease?

Answer 18

cells in basal ganglia degenerate

Question 19

What are symptoms of Huntington’s disease?

Answer 19

`