Basal Ganglia Flashcards
BG is Embryologically derived mainly from the_______. Components of it are also derived from the
telencephalon
diencephalon and the mesencephalon.
Location of BG
Located beneath the cerebral cortex and lateral to the dorsal thalamus
Striatum or neostriatum is composed of
- Caudate nucleus
* Putamen
Globus pallidus or paleostriatum made of;
- external or lateral segment (GPe)
* internal or medial segment (GPi)
Putamen and Globus Pallidus together are also known as the
lentiform or lenticular nucleus
Substantia nigra (in the midbrain) has two parts:
- pars compacta (SNc; dorsal): dopaminergic
* pars reticulata (SNr; ventral): GABAergic
pars compacta (SNc; dorsal) is
dopaminergic
pars reticulata (SNr; ventral) is
GABAergic
Nucleus accumbens is also the
Ventral striatum
Arterial supply of BG
Anterior cerebral artery–>
Middle cerebral artery–>
Posterior communicating artery
ACA–>medial staite artery
MIddle cerebral artery–> lateral striate and anterior choriodal artery
The Cortex NT
glutamate
The straitum (caudate and putamen) have these NTs
Ach, GABA, substance P, enkephalin
DIRECT PATHWAY:
The Striatum inhibits the inhibitory output from GPi and SNr to the Thalamus. Thus, the Thalamus is disinhibited (released from the inhibitory influence of GPi and SNr, i.e., excited), so it can excite the Cortex. Thus, MOVEMENT IS FACILITATED.
Direct Pathway: The Striatum_______ the inhibitory output from GPi and SNr to the Thalamus. Thus, the Thalamus is______ (released from the inhibitory influence of GPi and SNr, i.e., excited), so it can_____ the Cortex. Thus, MOVEMENT IS________.
inhibits
disinhibited
excite
FACILITATED
INDIRECT PATHWAY:
This pathway involves GPe and the Subthalamic nucleus (hence, Indirect). The Striatum inhibits the inhibitory output from GPe to the Subthalamic nucleus. The Subthalamic nucleus (released from the inhibitory influence of GPe) can excite the GPi and SNr to INHIBIT the Thalamus. The inhibited Thalamus is less able to excite the Cortex, so MOVEMENT IS INHIBITED
This pathway involves _________(hence, Indirect). The Striatum_______ the inhibitory output from GPe to the Subthalamic nucleus. The Subthalamic nucleus (released from the inhibitory influence of GPe) can_____ the GPi and SNr to________ the Thalamus. The inhibited Thalamus is less able to excite the Cortex, so _________
GPe and the Subthalamic nucleus inhibits excite INHIBIT MOVEMENT IS INHIBITED
Nigrostriatal pathway:
NT?
facilitates movement by acting on
dopaminergic;
both direct and indirect pathways.
Dopamine affects
2 different types of output neurons in the striatum:
Neurons with D1 dopamine receptors:
- Involved in exciting the Direct Pathway
* Hence, facilitate movement
- Involved in exciting the Direct Pathway
* Hence, facilitate movement
D1 dopamine receptors
Neurons with D2 dopamine receptors:
- Involved in inhibiting the Indirect Pathway (which inhibits movement) i.e., inhibiting the inhibitory pathway
- Inhibiting the inhibitory pathway leads to disinhibition of the thalamus
- Facilitate movement
- Involved in inhibiting the Indirect Pathway (which inhibits movement) i.e., inhibiting the inhibitory pathway
- Inhibiting the inhibitory pathway leads to disinhibition of the thalamus
- Facilitate movement
D2 dopamine receptors
D2 dopamine
• Involved in______ the Indirect Pathway (which inhibits movement) i.e., inhibiting the inhibitory pathway
• Inhibiting the inhibitory pathway leads to________ of the thalamus
•________ movement
inhibiting
disinhibition
Facilitate
end result of dopamine on both the Direct and Indirect pathways is the
FACILITATION OF MOVEMENT.
_______is the neurotransmitter of intrinsic neurons in the striatum.
Acetylcholine
Do cholingergic neurons project outside of the striatum
nope
They inhibit striatal neurons of the Direct Pathway
cholinergic neurons in striatum
Affect of cholinergic neurons in striatum on Indirect pathway
They excite striatal neurons of the Indirect Pathway
effects result in the INHIBITION OF MOVEMENT.
Aceytycholine
Cholinergic neurons in the striatum: effects result in the
INHIBITION OF MOVEMENT
Extrinsic inputs to the basal ganglia terminate mainly in the
striatum.
Where do extrinsic inputs to BG come from
cerebral cortex (motor, sensory, association and limbic)~ topologically organized Intralaminar nuclei of the thalamus: also topographically organized
Extrinsic outputs from the basal ganglia arise mainly from
globus pallidus and substantia nigra, pars reticulate (SNr).
Extrinsic outputs from the basal ganglia arise mainly from the globus pallidus and substantia nigra, pars reticulate (SNr). Both of them are_____.
GABAergic
Extrinsic outputs from the basal ganglia arise mainly from the globus pallidus and substantia nigra, pars reticulate (SNr). Both of them are GABAergic. They project to:
- Motor nuclei of the thalamus
* Superior colliculus of the midbrain
3 connection within the BG
Striatum (caudate and putamen)
Subthalmic nucuels
substantia niagra
How is the Basal ganglia involved in regulation of movement
Involved in the regulation of movement: through direct and indirect connections with the cerebral cortex, the basal ganglia influence descending motor systems
What role does the BG have in the extrapyramidal motor system?
Forms the major component of the extrapyramidal motor system; however, there is extensive interconnections and cooperation between the extrapyramidal and the pyramidal systems in the control of movement.
Three general functions of the BG?
Involved in the control of eye movements and in the memory of orientation in space.
Contributes to cognition.
Related to limbic functions.
Disorders of the basal ganglia is usually a disruption of
transmitter metabolism
Abnormal movements are commonly caused by a release of the system from
inhibition
Symptoms of BG dysfunction
Involuntary movements: tremor at rest, athetosis, chorea, ballism, and dystonia
Akinesia and bradykinesia
Changes in posture and muscle tone
Muscle rigidity
Degeneration of dopaminergic cells in SNc
• Tremor at rest, rigidity, and bradykinesia
Parkinsons Diseaese
Parkinsons is degeneration of __________ in the __________
dopaminergic
SNc
Degeneration of cholinergic and GABAergic neurons in the striatum
Huntingtons
Genetics of Huntingtons
inherited; mutation in chromosome 4 causes numerous CAG repeats (encodes for glutamine)
symptoms of Huntingtons
Chorea, athetosis, and dystonia
Tardive dyskinesia:
- Results from long term use of antipsychotic agents, which block dopamine transmission
- Involuntary movements, especially of the face and tongue
long term use of anti-psychotics that block dopamine transmission can cause
tardive dyskenesia
Tardive dyskinesia usually affects
face and tongue (get involuntary movements)
Hemiballismus:
- Lesion of the subthalamic nucleus
* Violent “ball-throwing” movements of the contralateral arm
Lesion of the subthalamic nucleus
Hemiballismus
- Lesion of the subthalamic nucleus
* Violent “ball-throwing” movements of the contralateral arm
Hemiballismus
Cerebellum has______ input from the spinal cord
BG has -_____
Direct
None
Cerebellum and BG have ______direct output to the spinal cord
no
Connections with the brain stem
Cerebellum
- Connects with and part of it is in the brain stem
BG
Cerebellum has _____ Input from the cortex
BG has _____ _input from the cortex
indirect
Direct
Both Cerebellum and BG projects via______ to the cortex
thalamus
Output from cerebellum is ________
Output from BG is _______
Excitatory
inhibitory
Coordinates execution of movements: compares intended with executed
cerebellum
Planning and execution of complex motor strategies: amplitude & velocity of movements
BG
Cerebellar Lesion:______ symptoms
BG Lesion:
ipsilateral
often contralateral symptoms, but can
be bilateral
Symptoms associated with Cerebellar lesion:
Ataxia, impaired balance, intentional tremor
Symptoms associated with BG lesion
Too much or too little movements, tremor at rest
