modulation of movement by the basal ganglia Flashcards
what is called the pyramidal pathway
executor pathway
in the extrapyramidal pathways what accessory pathways are the signals relayed thru
singals are relayed thru multiple pathways involving basal ganglia, cerebellum, brainstem nuclei
what is the function of basal ganglia, cerebellum, reticulospinal and vestibulospinal tracts, corticorubrospinal system
-basal ganglia: complex motor actions
-cerebellum: mvt coordination -reticulospinal and vestibulospinal tracts: antigravity and equilibrium
-corticorubrospinal system: fine motor control
basal ganglia consists of what 5 nuclei
Caudate
Putamen
Globus Pallidus
Substantia Nigra
Subthalamus
basal ganglia influences mvt by reg the activity of the umn circuits
-reg m. cnt
-F initiation and termination of mvt
-reg multi-jnt mvt
-Control movement sequencing,
-Oculomotor control (e.g. saccadic eye movement),
-Motor habit learning
what complex patterns of motor activity does the basal ganglia control
Writing,
Using scissors,
Throwing balls,
Shoveling dirt,
Some aspects of vocalization (speech),
what is the input zone
striatum: caudate, putamen
input zone receive and process mvt related signals from
Cerebral cortex,
Substantia nigra pars compacta (dopaminergic neurons).
what are the main neurons of the caudate and putamen
medium spiny neurons (inhibitory, GABA)
the axons from medium spiny neurons contact neurons of:
Globus pallidus (External
& Internal),
Substantia nigra pars reticulata (not SN pars compacta).
describe the output zone pathway (GP, VL/VM, motor cortex)
Neurons of the of internal segment of globus pallidus (inhibitory) –> Ventral anterior and ventral lateral complex nuclei of the thalamus (excitatory) –> Motor cortex on the frontal cortex (upper motor neurons)
describe output zone (SNPR and sup colliculus)
Neurones of the Substantia nigra pars reticulata (inhibitory) –> Superior colliculus (excitatory) that command head and eye movements
Efferent cells of globus pallidus internal and substantia nigra pars reticulata are ______
inhibitory
They have high levels of spontaneous activity
that prevent unwanted movement by ______ ______ cells in the
thalamus and superior colliculus.
tonically inhibiting
at resting state, describe the chain of n. cells arranged in a disinhibitory circuit
At resting state: Striatum
neuron (A) is silent, no
inhibition on Globus pallidus
neuron (B). Globus pallidus
neuron (B) is tonically inhibiting VA/VL thalamus neuron (C). No excitation of the motor neuron (D)
at initiation of voluntary (intended) movement, describe the chain of n. cells arranged in a disinhibitory circuit
Striatum neuron (A) is transiently excited by cortical inputs. Globus pallidus neuron (B) is transiently inhibited. The VA/VL thalamus neuron (C) is disinhibited (released from inhibition), so excitatory input can excite it. The upper motor neuron (D) is excited.
what does the direct pathway serve
serves to release the thalamic neurons from tonic inhibition practiced by the globus pallidus to facilitate the initiation of voluntary (intended) movement
what does the indirect pathway serve
serves to increase the level of tonic inhibition of the thalamic neurons in order to prevent unwanted movement
what pathway is seen as a brake
indirect pathway
what pathway is seen as a accelerator
direct pathway
what is the principle functions of basal ganglia in motor control in the direct pathway
facilitates the initiation of motor programs that express movement (i.e., promotes voluntary movement in targeted muscles)
what is the principle functions of basal ganglia in motor control in the indirect pathway
facilitates the suppression of competing or non-synergistic motor programs (i.e., inhibits movement in other muscles that do not contribute to overall wanted movement).
what is the result of both pathways
smooth and coordinated movements
what diseases do dysfunctions in the 2 pathways explain
parkinson’s and huntingdon’s
