Lecture 3: Basal Ganglia

Question 1

Answer 1

Question 2

Answer 2

Question 3

Describe the various basal ganglia pathways specifying the neurotransmitters and types of neurons involved.

Answer 3

Striatum recieves glutamatergic input from the planning motor cortex

Direct pathway: GABAergic neuron projects from striatum to GPi synpasing on GABAergic neurons.

Indirect pathway: GABAergic neurons extend from the striatum to the GPe synapsing on GABAergic neurons which extend from the GPe to the STN synapsing on Glutamatergic neurons. These Glutamatergic neurons extend from the STN to the GPi.

Both Pathways synapse onto GABAergic neurons that then project from the GPi to the VA-VL nucelus in the thalamus.

VA-VL nucleus also receives inputs from the cerebellum

Glutamatergic neurons extend from the VA-VL to the planning area of the motor cortex and helps to modulate primary motor cortex outputs.

Question 4

What sort of movements are HD described by?

Answer 4

• > Chorea; Wirthing, jerky, fast
• > Athetosis; Smooth, flowing, body moves away from midline and doesnt return

Question 6

How are PKD movements described?

Answer 6

• > Rigid, stiff, stooped.
• > Pill rolling tremor
• > Difficulty initiating movements
• > Loss of execurtive function b/c loss of dopaminergic systems, loss of drive, loss of thought processess.

Question 7

What are the function of the basal ganglia?

Answer 7

• Integrates smooth movement
• Mood through movement (i.e expressionism)
• Controls refined/fine movement

Question 8

Where does basal ganglia circuitry begin and end?

Answer 8

Begins and ends in the cortex which means they modulate the upper motor neurons (pyramidal cells)…

But the circuit is extra-pyramidal

Question 9

What can the substantia niagra be divided into?.

Answer 9

SN pars compacta and SN reticulate

Question 10

Where is the head of the caudate nucleus located? and where does is the tail located?

Answer 10

Lateral aspect of the anterior horn of the lateral ventricle and the anterior aspect is connected to the putamen. (together = striatum). The tail of the caudate nucleus follows the course of the lateral ventricle.

Question 11

What is the broad function of the thalamus?

Answer 11

Functions as a relay station for sensory information from the periphery to the cortex and as a relay station b/w the brain and its target organs/structures.

Question 12

Whats the clinical importance of the basal ganglia?

Answer 12

Diseases such as HDD, PKD, Tourettes are associated with basal ganglia dysfunction.

Question 13

What movements are regulated by the cerebellum and what changes that?

Answer 13

Ballastic movements are controlled by the cerebellum until that movement becomes learned/repeated then the BG takes over.

Question 14

What leads to tourettes?

Answer 14

Dysf of the STN

Tick is voice or movement

Question 15

What happens in parkinsons diseases?

Answer 15

• Loss of dopaminergic neurons extending from the SN to the striatum. These fibres are normally responsible for maintaining RMP, therefore cells in PKD become hyperpolarised and take a lot of glutamate from the cortex fibres to fire. Potentially leading to glutamate toxicity. It also means theres less firing of the straital cells to the GPi (direct pathway), less inhibition means these cells fire as much as they want, inhibiting the VA-VL fibres to the cortex = parkinsons

Question 16

What happens in HDD?

Answer 16

The GABAergic striatal->GPe are the first to die. = Less inhibition of GPe increases the rate of GABAergic firing onto the STN. This in turn decreases its Glutamatergic firing to the GPi = decreased inhibition of GPi->VA-VL (GABA) and in turn the VA-VL cells are able to fire more = Hyperexcitability of cortex, increased UMN firing = rhything movements

Late HDD loses the SNr-Dopamine->Striatum, = decreased GABA firing to GPI = Complete loss of inhibition. GABA fibre from GPi to VAVL can fire as much as it wants = Parkins like disease.

Question 17

What are the treatments for PD?

Answer 17

L-dopa

Deep brain stimulation

Question 18

Whats the function of the SNr in the basal ganglia?

Answer 18

Dopaminergic, maintains RMP of the GABAergic cells in the straitum. Allowing it to respond to the slightest Glutamate input from the cortex.

Question 19

Whats the most severe part of parkinsons?

Answer 19

Loss of dopaminergic systems can lead to mood and movement disorders.

Anti-depressants are the most common treatments.