The Basal Ganglia Flashcards
What Is the Basal ganglia?
It’s also called cerebral nuclei
It is masses of grey matter that are within each cerebral hemisphere deep to the floor of the lateral ventricle and are embedded in white matter of the cerebrum
What are the structures of the Basal ganglia?
Caudate nucleus -has a massive head and slender curving tail that follows the curve of the lateral ventricle the head lies anterior to lentiform nucleus
Lentiform nucleus
Lateral putamen and medial globes pallidus
What is the corpus striatum?
Striated body that is used to refer to caudate nucleus and Putam or caduate and lentiform nuclei
It has a striped appearance and the amygdaloid body lies in front of tail of caudate nucleus and inferior lentiform nucleus
What are the four structured of the Basal ganglia?
Stratum
Globes pallidus
Substantia nigra
Subthalamic nucleus
What is the striatum?
Major inputs to the Basal ganglia
It’s made of dorsal (made up of caudate and pitamen)and ventral striatum (made up of nucleus accumbens,septum abd olfactory tubercle)
What is the globes pallidus?
It is part of the telencephalon
It is the major component of the Basal ganglia
And divided into lateral and medial component
What is the substantia nigra?
A mid brain structure between red nucleus and cerebral penduncle
Divided into substantia nigra pars compacta(dark consists of dopamine synthesis)and reticulate(smaller most gabaeretic)
What is the subthalamic nucleus?
Part of the dicephalon
Neurons are excitory
Use glutamate
What is is the function of the Basal ganglia?
Influence muscle control
Regulate attention and cognition
Inhibit unnecessary movements
Regulate intensity of slow or stereotyped movements
What is the general pathway?
Info arrives at caudate nucleus and putamen from sensory,motor and interagency areas of cerebral cortex
Processing occurs in these nuclei and in adjacent globes pallidus
Most output of Basal nuclei leaves globes pallidus and synapses in the thalamus
What is the Basal ganglia feedback loop?
It is when you decide to start walking the Basal nuclei controls cycles of your arms and thighs with movement until you decide to stop walking
When you begin voluntary movement Basal ganglia will control and adjust muscle tone particularly in the apendicular muscles to set body position
What are the two important pathways in which striatal information reaches globes pallidus?
Direct and indirect pathway
What is the normal Basal ganglia circuitry in normal conditions?
Where excitation of the direct pathway has a net effect in exciting the thalamus neurons
And excitation of the indirect pathway has a net effect in inhibiting the thalamus neurons
What does the thalamus stimulate?
The motor cortex
What does the GPext and GPint do?
The GPext with excite thalamus and motor cortex and inhibits subthalamic nucleus
The GPint will inhibit the thalamus and motor cortex
What does the subthalamic nucleus do?
It excites the GPint neurons and promote inhibitation of thalamus and motor cortex
What is the function of glutamate?
It is an excitory neurotransmitter
What is GABA?
It is an inhibitory neurotransmitter
What is the function of dopamine?
It excites the direct pathway via D1 receptors
It inhibits indirect pathway via D2 receptors
What is the activity in the direct pathway?
In the direct pathway striatal neurons are fired and these will cause GPint to inhibit
The inhibitation will cause thalamic neurons to be released from inhibitation and allows to fire to excite the motor cortex
The GPext inhibits the subthalamic nucleus which excites the GPint
So the net results of exciting the direct pathway is firing striatum neurons which cause the motor cortex to excite
What does the indirect pathway do?
So the indirect pathway will wh2n striatum neurons are fired inhibit the Gpext which will disinhibit the subthalamic nucleus.
And the Gpint neurons will the inhibit thalamus neurons which will inhibit motor cortex
What is the Basal nuclei inhibited by?
Dopamine(the subtantia nigra releases neurons which inhibit Basal ganglia
What is an important pathway for modulation?
Dopamineregic
Direct pathway striatal neurons have D1 dopamine receptors which depolarize cell in response to dopamine
What is the nigrostriatal pathway?
It is the pathway where the substantia pars compacta to striatum
What hyperpolarizes the cell in response to dopamine?
Indirect striatal neurons which have D2 dopamine receptors
What is the two routes for net effect of exciting cortex from nigrostratal pathway?
Excites the direct pathway on cortex
Inhibits the indirect pathway
What is Parkinsons disease characterized by?
Bradykinesia
akinesia
Resting tumor
What is the cause of Parkinsons disease?
The loss of dopaminergic neurons in substantia nigra pars compacta
What is Huntington disease characteristized by?
Choreiform movements(involuntary continous movements of body)
