M3 L3 Flashcards

Question

How do medium spiny neurons help regulate movement?

Answer 1

by inhibiting other neurons in the basal ganglia circuit using GABA which is an inhibitory NT

Answer 2

The substantial nigra pars reticulate (SNr) and GPI

Answer 3

both GPI and GPE

Answer 4

1. Cortical pyramidal neurons 2. Dopaminergic (DA) neurons - which receive inout from SNr 3. Local circuit neurons

Answer 5

interneurons found in the spinal cord and brain, responsible for modulating and coordinating movement by connecting different neurons within a local area. * yes because they are close to the cell body so they're fast and have more influence * on cell body not dendrite

Answer 6

modulates synapses - specifically pyramidal neurons

Answer 7

because of their inward rectifier K⁺ (potassium) channels, which help maintain them in a hyperpolarized (inhibited) state at rest. Inward rectifier K⁺ channels allow potassium to flow into the neuron at resting membrane potentials, keeping the neuron more negative inside and making it less likely to fire. These channels close when the neuron becomes depolarized, allowing MSNs to become active only when they receive strong excitatory input (e.g., from the cortex).

Answer 8

– Receives cortical projections from multimodal association area and from frontal lobe eye movement area – Neurons in the caudate fire prior to eye movement

Answer 9

Receives inputs from the primary and secondary somatic sensory cortices in the parietal lobe, the visual cortices in the occipital and temporal lobe, the premotor and motor cortices from the frontal lobe, and the auditory association area from the temporal lobes * In the putamen, neurons fire action potentials in anticipation of limb and trunk movement

Answer 10

relay information from the cerebellum to the spinal cord via the rubrospinal tract, which influences motor neuron activity and muscle tone, particularly in flexor muscles

Answer 11

* Caudate * Putamen * sub thalamic nucelus * GPe * GPi

Answer 12

because they rely on excitatory input from the cortex and thalamus to fire action potentials. The striatum primarily receives excitatory (glutamatergic) input from the cortex. Without this input, the neurons in the caudate and putamen remain relatively silent.

Answer 13

Yes, the caudate and putamen are inhibitory because their MSNs release GABA, which is an inhibitory neurotransmitter. When activated, they inhibit their target structures in the basal ganglia, mainly the globus pallidus internus (GPi) and substantia nigra pars reticulata (SNr).

Answer 14

* Globus Pallidus Internus (GPi) * Substantia Nigra Pars Reticulata (SNr) * Globus Pallidus Externus (GPe) * Subthalamic Nucleus (STN)

Answer 15

The STN is spontaneously active but excitatory (glutamatergic), meaning it continuously stimulates the GPi/SNr, reinforcing their inhibition of movement.

Answer 16

The GPe is also spontaneously active and inhibits the subthalamic nucleus (STN) as part of the indirect pathway.

Answer 17

Both GPi and SNr are GABAergic (inhibitory) and fire continuously at rest, meaning they are always sending inhibitory signals to their targets (e.g., the thalamus and superior colliculus). This constant inhibition prevents unwanted movements.

Answer 18

Thalamus (VA/VL nuclei) → Motor Cortex * The thalamus is constantly inhibited by the GPi/SNr, which prevents it from exciting the motor cortex and triggering movements. Superior Colliculus (SC) → Eye Movements * The superior colliculus is tonically inhibited by the SNr to prevent unwanted saccadic eye movements.

Answer 19

The thalamic is inhibited and no info can get to the cortex * tonic inhibition * GP is inhibitory - if the striatum is inactive and doesn't block her - then she attacks thalamus - no info sent

Answer 20

if striatum is active then she inhibits Gpis powers which means the thalamus is free to communicate

Answer 21

When striatum active - Snr itself is inhibited and cannot block superior colliculus - eye movement occurs (if u need to quickly look to see a car coming) When striatum inactive - Snr is active and inhibits the superior colliculus - no eye movement (ur reading a book and ned to lock in)

Answer 22

because their neurons fire continuously at rest, even when no movement is happening. so when the striatum is inactive, the GP will fire and do her thing

Answer 23

* Direct pathway * Indirect pathway * Hyperdirect pathway

Answer 24

The direct pathway in the basal ganglia facilitates movement by reducing inhibition on the thalamus, allowing it to excite the motor cortex. * EXCITATORY

Answer 25

When the direct pathway is inactive, the motor cortex receives less excitation from the thalamus. if the direct pathway is inactive, this means the cerebral cortex is not strongly sending signals to the striatum, which means that the striatum is not active and doing its thing (needs to be stimulated to speak), which means that the Gpi is free to do her thing and inhibit the thalamus, which means no thalamus and cortex communication. * overall inhibitory if inactive

Answer 26

When the direct pathway is active, the overall effect is excitatory, leading to movement. if the direct pathway is active, this means the cerebral cortex is sending signals/stimulation to the striatum which means the striatum is active and able to do her thing and inhibit the Gpi which means the Gpi is blocked off and can't inhibit the thalamus, so the thalamus speaks to the cortex to produce movement. * overall excitatory

Answer 27

through medium spiny neurons (MSNs), which are the main output neurons of the striatum. How it works: 1) The cerebral cortex sends excitatory glutamatergic signals to the striatum. This activates medium spiny neurons (MSNs) in the striatum. 2) Medium spiny neurons (MSNs) in the striatum become active and release GABA (inhibitory neurotransmitter). 3) GABA inhibits the GPi, reducing its activity.

Answer 28

The indirect pathway of the basal ganglia is the movement-suppressing pathway. It works opposite to the direct pathway by increasing inhibition of the thalamus, making movement less likely to occur. * overall inhibitory

Answer 29

If the indirect pathway is inactive, this means it is not suppressing movement, so movement is more likely to occur. * if the indirect pathway is inactive, then the cerebral cortex is not stimulating the striatum. if the striatum isn't stimulated, it doesn't do its job to inhibit the Gpe. This means Gpe uses her power to inhibit STN and Gpi. If STN is inhibited, it can't turn on Gpi. SO Gpi and STN are out which means the thalamus is free to speak with the cortex * overall excitatory

Answer 30

if the indirect pathway is active, this means that the cerebral cortex is stimulating the striatum which means it is actived and inhibiting the GPe. If the GPe is blocked off, then no one is inhibiting the STN which means the STN can then activate GPi. so now GPi can do her thing and block off the thalamus so not communication with thalamus. * Overall inhibitory

Answer 31

In the direct pathway, we’re trying to reduce GPi activity so the thalamus can be free. We don’t need extra reinforcement—just turning off GPi is enough. But in the indirect pathway, we want to maximize GPi activity so it fully suppresses movement. That’s why the STN is necessary—it gives GPi the extra push to do its job properly.

Answer 32

The hyperdirect pathway is another route in the basal ganglia that acts as a fast brake on movement.

Answer 33

When it is active, the cerebral cortex sends excitatory signals (glutamate) to the STN which means the STN is activated and then excites the GPi and then the GPi does her thing and sends GABA to turn off the thalamus. no communication w cortex no movement * inhibitory

Answer 34

when inactive, the cerebral cortex does not send signals to the STN. So the STN is never able to stimulate/excite the GPi which means the thalamus gets to communicate with the cortex. * excitatory

Answer 35

it is myelinated

Answer 36

direct: Facilitates movement by reducing inhibition of the thalamus indirect: Suppresses unwanted movement by increasing inhibition of the thalamus

Answer 37

* Cells of the SN form dopaminergic synapses * SNc sends dopaminergic projections to the medium spiny neurons and acts on D1 and D2 receptors in the striatum (putamen & caudate) to modulate movement:

Answer 38

Dopamine modulates the basal ganglia by adjusting the strength of the direct and indirect pathways through its action on D1 and D2 receptors in the striatum. D1 and D2 Receptors are found on the medium spiny neurons (MSNs) in the striatum.

Answer 39

D1 receptors increase the direct pathway when dopamine binds to D1 receptors, which are excitatory (Gs-coupled). This will increase cAMP which makes the medium spiny neurons in the striatum more active. This means the striatum (the MSNs really) will inhibit GPi more using GABA which means GPi can't inhibit the thalamus. Thalamus speaks * they are excitatory and result in more movement

Answer 40

Dopamine binds to D2 receptors in the indirect pathway, which are inhibitory (Gi-coupled). This decreases cAMP, which reduces the striatum's (MSNs put less GABA onto GPe) inhibition of GPe which means it uses it powers to inhibit the STN. If STN is inhibited, it can't activate GPi and so GPi doesn't inhibit the thalamus. Thalamus speaks

Answer 41

More cAMP = More excitability * D1 neurons fire more, inhibiting GPi, allowing movement). Less cAMP = Less excitability * D2 neurons fire less, meaning they don't strongly inhibit GPe, allowing GPe to suppress STN, reducing movement inhibition

Answer 42

G protein coupled (metabotropic)

Answer 43

Hypokinesia = Too little movement Caused by: Overactive indirect pathway or underactive direct pathway (maybe too much inhibition of thalamus) Ex: Parkinson’s disease (slow movements, rigidity, bradykinesia)

Answer 44

Hyperkinesia = Too much movement Caused by: Overactive direct pathway or underactive indirect pathway (not enough thalamus inhibition) Ex: Huntington’s disease, Tourette’s, dyskinesias (excess involuntary movement)