Basal Ganglia - Friedman - Exam 1

Question 1

Basal Ganglia Functions:

Action selection

Plan and movement sequences

Integrate cortical inputs

Cognitive goals

Emotional goals

Survival oriented motivations

Moment by moment sensory inputs

Substrate for ____ learning

Substrate for ___ behaviors (why people get addicted)

Substrate for reward

Answer 1

Basal Ganglia Functions:

Action selection

Plan and movement sequences

Integrate cortical inputs

Cognitive goals

Emotional goals

Survival oriented motivations

Moment by moment sensory inputs

Substrate for procedural learning

Substrate for habitual behaviors (why people get addicted)

Substrate for reward

Question 2

There are a set of circuits that run through all the structures in the basal ganglia. They all have different functions.

Which three did Dr. Friedman talk about and what are their functions?

___ loop: has to do with cognitive function, attention, making decisions about what to do next, changing behaviors.

___ loop: has to do with emotional behaviors.

___ loop: body movement loop.

These loops are not independent of each other. Instead, they overlap.

Answer 2

There are a set of circuits that run through all the structures in the basal ganglia. They all have different functions.

Which three did Dr. Friedman talk about and what are their functions?

Pre-frontal loop: has to do with cognitive function, attention, making decisions about what to do next, changing behaviors.

Limbic loop: has to do with emotional behaviors.

Motor loop: body movemebt loop.

These loops are not independent of each other. Instead, they overlap.

Question 3

There are two parts in the motor loop of the basal ganglia:

What are they?

Answer 3

Indirect loop: inhibiting loop

Direct loop: allowing loop

Question 4

All voluntary movements are planned and carried out by what structure?

Answer 4

Cerebral cortex

Question 5

At any given time, multiple plans and multiple movements are being programmed by the cortex.

The cortex sends its info to the ___ ____.The __ ___ does some sort of processing and in the end, selects a movement. The purpose of the __ ____ is to select a movement.

All of the input from cortex to ganglia is to the ____. This structure is made up of the ___ and ___. For the motor system, the input is the ___).

Answer 5

At any given time, multiple plans and multiple movements are being programmed by the cortex.

The cortex sends its info to the BG.The BG does some sort of processing and in the end, selects a movement. The purpose of the BG is to select a movement.

All of the input from cortex to ganglia is to the striatum. This structure is made up of the caudate and putamen. for the motor system, the input is the putamen

Question 6

Dopamine is a NT and it comes from the ___ ___ part of the basal ganglia.

Answer 6

Substantia niagra

Question 7

The D1 receptors (exictatory or inhibitory?) projects directly to the ___ ___ ___. The __ __ is the output of the basal ganglia and projects to the thalamus within the direct/indirect system of the basal ganglia. The __ __ inhibits the thalamus and causes movement/no movement?

Answer 7

The D1 receptors (exictatory) projects directly to the globus pallidus internus. The globus pallidus internus is the output of the basal ganglia and projects to the thalamus within the direct system of the basal ganglia. The globus pallidus inhibits the thalamus and causes movement.

Question 8

The D1 neurons in the putamen inhibit the globus pallidus, then the thalamus is released and it excites the motor cortex, causing ___

Answer 8

The D1 neurons in the putamen inhibit the globus pallidus, then the thalamus is released and it excites the motor cortex, causing movement.

Question 9

All of the neurons within the basal ganglia are inhibitory except for two: neurons from the __ and __

Answer 9

All of the neurons within the basal ganglia are inhibitory except for two: neurons from the thalamus (VA/VL) and STN (subthalamic nucleus)

Question 10

The pathway that starts from the D2 containing neurons is more complicated. It projects to the ____ segment of the __ ___ (this normally inhibits the subthalamic nucleus).

But, when D2 is released, the ___ segment of the __ __ gets inhibited, causing the ___ nucleus to become activated.

The ____ nucleus activates the internal segment of the globus pallidus, which causes inhibition of the thalamus, and therefore, a decrease in ___ (there is a leash on the dog).

So, when the ___ pathway is predominant, you do not get movement. When the ___ pathway is predominant, you get movement.

Answer 10

The pathway that starts from the D2 containing neurons is more complicated. It projects to the external segment of the globus pallidus (the GpE normally inhibits the subthalamic nucleus).

But, when D2 is released, the external segment of the globus pallidus gets inhibited, causing the subthalamic nucleus to become activated.

The subthalamic nucleus activates the internal segment of the globus pallidus, which causes inhibition of the thalamus, and therefore, a decrease in movement (there is a leash on the dog).

So, when the indirect pathway is predominant, you do not get movement. When the direct pathway is predominant, you get movement.

Question 11

You must have an active thalamus exciting the cortex to get ____. Movement can only occur when the output of basal ganglia is ____.

Answer 11

Movement.

Movement can only occur when the output of the basal ganglia is reduced.

Question 12

The substantia nigra has two parts:

Answer 12

1. pars compacta - contains dopamine neurons
2. pars reticula (SMR) - it is just like the internal segment of the globus pallidus. They both project to the thalamus.

Question 13

The ___ pathway of the BG faciliates movement. The ___ pathway of the BG suppresses unselected movements.

Answer 13

The direct pathway of the BG faciliates movement. The indirect pathway of the BG suppresses unselected movements.

Question 14

The indirect and direct pathway of the BG are chemically distinct.

The ___ pathway uses:

D1 receptors

Substance __

Dy____

Projects to __ segment of the globus pallidus.

The ___ pathway uses:

D2 receptors

Enk__

Projects to __ segment of the globus pallidus.

Answer 14

The indirect and direct pathway of the BG are chemically distinct.

The direct pathway uses:

D1 receptors

Substance P

Dynorphin

Projects to internal segment of the globus pallidus.

The indirect pathway uses:

D2 receptors

Enkephalin

Projects to external segment of the globus pallidus.

Question 15

With Huntington’s Disease, a degenerative disease of the __ __ and cortex, the ___ neurons degenerate first (aka D2 neurons).

Answer 15

With Huntington’s Disease, a degenerative disease of the BG and cortex, the enkephalon neurons degenerate first (aka D2 neurons).

Question 16

The subthalamic nucleus’s role is to excite ____ segment of the globus pallidus, and ___ movement.

The subthalamic nucleus receives tonic inhibitory input from the ___ segment of the ___ ___.

The STN can also receive direct cortical inputs, which inhibits movement. This is called the __direct pathway.

Answer 16

The subthalamic nucleus’s role is to excite internal segment of the globus pallidus, and inhibit movement.

The subthalamic nucleus receives tonic inhibitory input from the external segment of the GP.

The STN can also receive direct cortical inputs, which inhibits movement. This is called the hyperdirect pathway.

Question 17

__ ___ is a sheet of neurons in the midbrain between the cerebral peduncles and tegmentum of midbrain.

The dorsal part of the sheet houses the dopamine.

The ventral parts, the pars reticulata, and just like the ones in the the internal segment of the GP, are GABAnergic or inhibitory. So. the dopamine neruons project back into the striatum, but also to the entire BG. It is these guys who die in Parkinsons disease.

Answer 17

Substantia Nigra is a sheet of neurons in the midbrain between the cerebral peduncles and tegmentum of midbrain.

The dorsal part of the sheet houses the dopamine.

The ventral parts, the pars reticulata, and just like the ones in the the internal segment of the GP, are Gaba nergic or inhibitory. So the dopamine neruons project back into the striatum, but also to the entire BG. It is these guys who die in Parkinsons disease.

Question 18

Which one, A or B, is the one with Parkinson’s Disease?

Answer 18

A

Dopamine neurons accimulate melanin, giving the SNc a dark color (NORMAL)

The loss f pigmentation shows the loss of dopamine neurons (the left one)

Question 19

T or F?

Dopamine faciliates movement through both indirect and direct pathways.

Answer 19

T

D1 receptors are excitatory. Dopamine activates the direct path, which activates mvmt.

D2 receptors are inhibitory. Dopamine inhibits the indirect path, which activates mvmt.

Question 20

One alternative to treating Parkinson’s disease is Deep Brain Stimulation, which inactivates specific targets in the brain by electrical stimulation.

Given what you know about the circuitry of the basal ganglia, what structure would you inactivate to help with the hypokinetic symptoms of PD?

Answer 20

You could inactivate the subthalamic nucleus (prevent the release of glutamine, which activates GPI, which, when activated, releases inhibitory neurons to the thalamus, preventing movement).

You could also inactivate the Globus Pallidus internus. If you inactivate GPi, the thalamus is not held on a leash anymore, so it causes movement.

Question 21

Medium spiny neurons (MSNs), also known as spiny projection neurons, are a special type of ___-nergic inhibitory cell representing 95% of neurons within the human striatum, a structure located in the basal ganglia. Medium spiny neurons have two primary phenotypes (i.e., characteristic types): __-type MSNs of the direct pathway and ___-type MSNs of the indirect pathway

Answer 21

Medium spiny neurons (MSNs), also known as spiny projection neurons, are a special type of GABA-ergic inhibitory cell representing 95% of neurons within the human striatum, a structure located in the basal ganglia. Medium spiny neurons have two primary phenotypes (i.e., characteristic types): D1-type MSNs of the direct pathway and D2-type MSNs of the indirect pathway

Question 22

Two types of cholinergic receptors are:

Answer 22

muscarinic and nicotinic

Question 23

Cholinergic interneurons predominantly excites the __ pathway.

This balances the inhibitory effect of dopamine (inhibitory effect of dopamine on the ___ pathway causes movement).

The ___ ___ can amelioriate akinesia of PD by blocking excitatory effects of cholinergic interneurons.

Answer 23

Cholinergic interneurons predominantly excites the indirect pathway.

This balances the inhibitory effect of dopamine (inhibitory effect of dopamine on the indirect pathway causes movement).

The muscarinic anticholinergics can amelioriate akinesia of PD by blocking excitatory effects of cholinergic interneurons

Question 24

When there is no dopamine, you get this excitatory effect of ACh on the indirect pathway, which would inhibit __ – not a good thing for someone with PD. If you can block that, you would facilitate ___ – a good thing for people with PD.

Answer 24

When there is no dopamine, you get this excitatory effect of ACh on the indirect pathway, which would inhibit mvmt – not a good thing for someone with PD. If you can block that, you would facilitate mvmt – a good thing for people with PD.

Question 25

Dyskinesia is called by lesions of the ___ ___.

Dyskinesia - abnormality or impairment of voluntary movement.

Dyskinesia comes in two classes:

___ and ___

___ includes tremor, ballism, chorea, tics

___ includes rigidity, bradykinesia, akinesia

Answer 25

Dyskensia is called by lesions in the Basal Ganglia

Dyskinesia - abnormality or impairment of voluntary movement.

Dyskinesia comes in two classes:

1. Hyperkinetic includes - tremor, ballism, chorea, tics
2. Hypokinetic includes - rigidity, bradykinesia, akinesia

Question 26

___ is a hyperkinetic disorder which causes an uncontrolled flinging motion of the limbs. It is caused by the unilateral lesion of the ___ nucleus.

Answer 26

Ballism causes an uncontrolled flinging motion of the limbs. It is caused by the unilateral lesion of the subthalamic nucleus.

Question 27

A unilateral subthalamic nucleus lesion such as in a stroke due to a __ __ artery occlusion, gets rid of the excitatory drive on the internal segment of the GP. The thalamus is not inhibited, and is free to act on the motor cortex, causing wild flinging, uncontrolled mvmt of limbs as in ____.

Answer 27

A unilateral subthalamic nucleus lesion such as in a stroke due to a post choroidal artery occlusion, gets rid of the excitatory drive on the internal segment of the GP. The thalamus is not inhibited, and is free to act on the motor cortex, causing wild flinging, uncontrolled mvmt of limbs as in hemiballismus.

Remeber, motor neurons (cortico-spinal tract) cross in the pyramidal decussation of the medulla, so all deficits will be contralateral. So if something is seen on the left side, (for example wild flailing of the left arm or leg in hemiballismus), then that would mean the lesion in the STN is on the right side.

Question 28

___ disease is an autosomal dominant degenerative disease. There is progressive cell death in the striatum and frontal cortex.

Enkephalin-containing neurons (D2) die first, therefore, there is a loss of the indirect pathway (causing uncontrolled mvmt).

It also cause Chorea, eventually dementia and psychiatric disorders, and death

Answer 28

Huntingtons disease is an autosomal dominant degenerative disease. There is progressive cell death in the striatum and frontal cortex.

Enkephalin-containing neurons (D2) die first, therefore, there is a loss of the indirect pathway (causing uncontrolled mvmt).

It also cause Chorea, eventually dementia and psychiatric disorders, and death

Question 29

Essential tremor is idiopathic. It may be diministed with ___ or __ blockers.

Answer 29

alcohol or beta blockers

Question 30

Rigidity is a classic __ ___ sign. It causes increased limb resistance to passive mvmt such as in lead pipe rigidity.

In ___, there is constant resistance throughout bending (cogwheel rigidity). This is different from ____, which demonstates the clasp-knife reflex.

So, basal ganglia disorders give you ____, whereas UMN disorders give you ____.

___ - ratchet-like interruptions in tone throughout limb bending – may be due to tremor on top of rigidity.

Answer 30

Rigidity is a classic basal ganglia dysfunction sign. It causes increased limb resistance to passive mvmt such as in lead pipe rigidity.

In rigidity, there is constant resistance throughout bending (cogwheel rigidity). This is different from spasticity which demonstates the clasp-knife reflex.

So, basal ganglia disorders give you rigidity, whereas UMN disorders give you spasticity.

Parkinsonian - ratchet-like interruptions in tone throughout limb bending – may be due to tremor on top of rigidity.

Question 31

Spasticity vs Rigidity:

Corticospinal tract lesions (UMN) demonstrate increase tone in leg extensors and arm flexors (decorticate rigidity). The resistance to mvmt varies with ___. It also causes deep tendon reflexes like __ __ and ___.

Basal ganglia lesions cause increased resistance to any mvmt. It is independent of ___ as seen in __ ___ and ___ wheel.

The limbs also stays where they are placed.

Answer 31

Spasticity vs Rigidity:

Corticospinal tract lesions (UMN) demonstrate increase tone in leg extensors and arm flexors (decorticate rigidity). The resistance to mvmt varies with speed. It also causes deep tendon reflexes like clasp knife and clonus.

Basal ganglia lesions cause increased resistance to any mvmt. It is independent of speed as seen in lead pipe and cogwheel.

The limbs also stays where they are placed.

Question 32

__ ___ disorders can lead to both positive and negative motor signs

Many symptoms can be explained by the balance of activity in the __ and __ pathways

Basal Ganglia disorders (such as in ___ disease) lead to ____, whereas UMN diosrders lead to ___

Rigidity is useful diagnostic symptom

Answer 32

Basal Ganglia disorders can lead to both positive and negative motor signs

Many symptoms can be explained by the balance of activity in the direct and indirect pathways

Basal Ganglia disorders (such as in Parkinson’s disease) lead to rigidity, whereas UMN diosrders lead to spasticity.

Rigidity is useful diagnostic symptom