Brainstem Flashcards
Basal ganglia primarily concerned with
posture
movement
muscle tone
basal ganglia consists of
stratum (caudate and putamen) and globus pallidus
extrapyramidal system consists of
- basal ganglia
- substantia nigra (pars reticulata & pars compacta)
- subthalamic nucleus
ventral striatum
nucleus accumbens
dorsal striatum
caudate
putamen
nucleus accumbens is where the ..
caudate and putamen meet
main input to striatum
cerebral cortex
interconnections of basal ganglia loop
cerebral cortex ACTIVATES striatum –>INHIBITS globus pallidus & substantia nigra pars reticulata–>INHIBITS thalamus–>ACTIVATES cerebral cortex
globus pallidus and substanta nigra also inhibit
superior colliculus
substantia nigra pars compacta
reciprocal connection with striatum
subthalamic nucleus
activates globus pallidus and substantia nigra, but they project back and inhibit it
dysinhibition
inhibition of an inhibitor–>net result is activation
2 pathways through basal ganglia and what do they do
Direct- facilitates movement
Indirect- inhibits movement
Direct Pathway
substantia nigra pars compacta
–> send transient D1 projections to striatum–>this allows striatum to inhibit globus pallidus (internal)–>which lifts inhibition on thalamus–> excites frontal cortex
==>net excite
indirect pathway
cerebral cortex excites striatum–>this causes striatum to inhibit gp external segment–>gp usually inhibits subthalamic nucleus ,so now the subthalamic nucleus is excited–>excites gp internal–>when gp internal is activated it inhibits Va/Vl of thalamus
==>net inhibit
dopamine D2 vs D1
D1 (direct pathway) D2 (indirect)
both go from SN–>Striatum
D1 excites
D2 inhibits
net effect of both is excitatory
2 functional considerations of Basal Ganglia
segregation- separated circuits within basal ganglia
–>subcircuits: primary motor, premotor, supp motor
convergence- many cerebral cortical neurons–> less striatal neurons–>even less globus pallidus neurons
Motor Loop
motor, premotor, somatosensory cortex–>putamen–>lateral globus pallidus, internal–>ventral lateral and ventral anterior nuclei
occulomotor loop
frontal eye field, supp eye field
posterior parietal, prefrontal cortex
- ->caudate
- ->globus pallidus, internal
- ->mediodorsal and ventral anterior nuclei
OR
- ->caudate
- ->substantia nigra pars reticulata
- ->superior colliculus (direct involved in eye movement)
prefrontal loop
dorsolateral prefrontal cortex
- ->anterior caudate
- -> globus pallidus, int AND substantia nigra, parts reticulata
- ->mediodorsal and ventral anterior nucleui
limbic loop
amygdala, hippcampus, orbitofrontal cortex, anterior cingulate cortex, temporal cortex
- ->ventral striatum
- ->ventral pallidum
- ->mediodorsal nucleus
only areas of cortex that do not project to striatum
primary visual
primary auditory
3 types of neurons in striatum
medium spiny neurons
cholingergic interneurons
enkephalingergic interneurons
what do all neurons of striatum contain
GABA
mesolimbic dopamine reward system
increase in DA transmission from neurons of VTA–>nucleus accumbens
Initiation of movement
parietal cortex (posterior to post central gyrus)–> premotor–>motor
projections to cerebellum are greatest when
movement is novel
VTA sends what to what
D3, D4 Da neurons to inhibit nucleus accumbens
