Basal Ganglia Animation

Basal Ganglia Animation

May 2012

Movement in the body is controlled by the brain. Working in conjunction with motor neurons (neurons that connect to muscles), the brain sends signals to muscles to contract. A combination of these signals results in either a wanted movement or the stopping of an unwanted movement.

Brain

Motor Neurons

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Show movement when “signal” reaches the hand

Show signal going from brain to hand (brain to

motor neurons to hand)

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The motor cortex sends out signals to control voluntary movements in the body via motor neurons that cause muscle to contract.

Motor Neurons

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Show movement when “signal” reaches the hand

Show signal going from brain to hand (motor cortex to motor neurons to hand)

Motor Cortex

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The control of voluntary movement by the motor cortex, however, is regulated by other brain circuits. One of these is called the basal ganglia, a group of interconnected structures in the middle of the brain. Specifically, the basal ganglia participate in the initiation and termination of voluntary movements by suppressing unwanted movements and permitting desired and appropriate movements .

Motor Neurons

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Show movement when “signal” reaches the hand

Show signal going from brain to hand (motor cortex to spinal cord, spinal cord to motor neurons, motor neurons to arm and hand muscles AND back and forth between motor cortex and basal ganglia)

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Basal Ganglia

Motor Cortex

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Transition from prior screen: Zoom in on brain and fade basal ganglia area to the actual structures

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Basa

l Gan

glia

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The basal ganglia consists of the striatum (caudate nucleus and putamen),

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Striatum

global pallidus (external and internal segments),

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subthalamic nucleus,

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Even though I “cut” out the structures, I would recommend just fading them and highlighting the structure being addressed.

and substantia nigra reticulata.

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The basal ganglia receives information from most parts of the cerebral cortex and sends information specifically to the motor cortex, to execute movement, through the thalamus.

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So, how does this process work? Messages are sent from various parts of the cerebral cortex to the

basal ganglia, here let’s consider messages from the motor cortex to the striatum, the input structure of

the basal ganglia.

Striatum

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Motor Cortex

Striatum

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Keep the highlighting cycling until student moves on to next section.

The basal ganglia also has output structures, the globus pallidus internal segment and the substantia nigra reticulata, which control the motor

cortex through the thalamus. (N.B. erase big arrow and unhighlight the striatum and highlight the SNr and Gpi as output structures with an arrow going to the thalamus and another arrow going to the motor

cortex.)

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The globus pallidus internal segment and the substantia nigra reticulata control the motor cortex through the thalamus.

1. Have these be dynamic, dashed arrows that appear first and then highlight the thalamus.

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Third – make this a dynamic, dashed line.

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The striatum controls the output structures through two different pathways.

Striatum

Global pallidus external segment

Subthalamic Nucleus

Global pallidus internal segment/Substantia

nigra reticulata

Indirect Pathway: Suppresses unwanted or inappropriate movements.

Direct Pathway: Promotes wanted or desired movement

In the indirect pathway, the striatum sends a message to the global pallidus external segment .

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Striatum

Global pallidus external

Striatum

Global pallidus external segment

The global pallidus external then sends a signal to the subthalamic nucleus.

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Global pallidus external

Global pallidus external segment

Subthalamic nucleus

Striatum

The subthalamic nucleus then sends a message to the global pallidus internal and substantia nigra.

Subthalamic nucleus

Global pallidus internal segment/Substantia

nigra reticulata(Output)

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Subthalamic nucleus

Global pallidus internal segment

Substantia nigra reticulata

Global pallidus external segment

Striatum (Input)

The striatum also sends messages through the direct pathway. In this pathway, the striatum sends a message directly to the global pallidus internal and the substantia nigra.

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Striatum

Global pallidus internal segment/substantia nigra

reticulata

Now the global pallidus internal and the substantia nigra have received

messages from both the indirect and direct pathway. Motor cortex

Striatum

Global pallidus external

Subthalamic nucleus

Global pallidus internal/Substantia nigra

Direct Pathway

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rect

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hway

The global pallidus internal and substantia nigra then send a

message on to the thalamus.

Substantia nigra

Global pallidus internal

Thalamus

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Motor cortex

Striatum

Global pallidus internal/Substantia

nigra

Thalamus

Indirect pathway

Direct pathway

The thalamus then sends a message t o the motor cortex.

Thalamus

Motor Cortex

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Motor cortex

Striatum

Global pallidus internal/Substantia

nigra

Thalamus

Direct pathwayIn

dire

ct p

athw

ay

The motor cortex then sends the appropriate

message out to the body.Motor Cortex Highlight first

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