Exam 2- week 7 ppt 5 Cerebrum Basal Nuclei Connections Patho Flashcards
___ circuits have been described within the basal nuclei (origin and project)
3-5
~All of the pathways originating in various areas of cerebral cortex
~Cerebral cortex projects to the caudate nucleus, putamen, and nucleus acumbens
circuits of the basal ganglion- main outputs
from globus pallidus (internus) & substantia nigra (pars reticulata)
basal ganglion: efferent terminate in
the thalamus
~VA and VL- motor
~DM- cognitive
basal ganglion: thalamus then projects
back to the cerebral cortex
names of tracts for connections
~ansa lenticularis
~lenticular fasciculus
~nigro-thalamic
Ansa lenticularis: location
~arises from the ventral surface of globus pallidus
~passes anteriorly through GP
~loops around the posterior limb of the internal capsule
~joins with lenticular fasciculus to form the ventral part of the thalamic fasciculus which ends in VA/VL thalamus
Lenticular fasciculus: location
~from BN (globus pallidus) to the thalamus
~penetrates directly thru internal capsule
~is dorsal to ansa
~joins with ansa to form thalamic fasciculus which ends in VA/VL thalamus
Nigro-thalamic: location
~from basal nuclei to thalamus
~arises from pars reticulata of substantia nigra
~runs dorsal to internal capsule to end in VA/VL thalamus
Generally the connection through the BG are defined as
direct or indirect pathways
direct pathways involves what pathway
Excitatory glutaminergic pathway from cortex to putamen
direct pathway: details with putamen
~stimulates neurons in the Putamen which in turn produces GABAnergic inhibition of inhibitory GABA output from globus pallidus to thalamus.
~excites the Putamen to inhibits globus pallidus inhibition of thalamus.
direct pathway: details with thalamus
Excited thalamic neurons which in turn excites motor cortex to produce movement
disinhibition (what is it)
produced by a excitation of an inhibition of an inhibitory pathway to produce excitation
disinhibition (and the putamen)
excited Putamen which inhibits the GP inhibition of thalamus to excite thalamus
indirect pathway: excitatory pathway
Excitatory glutaminergic pathway from cortex to putamen
indirect pathway: and putamen
Putamen GABAnergic inhibition produces inhibition of the inhibitory GABA output from globus pallidus externus to subthalamus
indirect pathway: and subthalamus
excites globus pallidus internus
indirect pathway: and GP internus
inhibits the thalamus, which can no longer excite the cortex
~the unexcited motor cortex will fail to produce movement
Goal of direct pathway
increase movement
Goal of indirect pathway
decrease movement
changes in muscle tone can be seen with damage in different parts of
the basal nuclei
types of changes in muscle tone
~hypertonia
~hypotonia
~combination of the two
~cogwheel rigidity
hypertonia
rigidity
hypotonia
falccidity
Resting tremor
~Rhythmic, alternating movement of a body part
~Variable frequency and amplitude based upon disease process
~Parkinson’s disease has between 4-5 Hz with increasing amplitude with progression
Chorea
~Brisk, large, complex movements
~Resemble fragments of purposeful movements
~May incorporate them into movement
~Huntington’s chorea or overdosing with Parkinson’s meds
Athetosis
~another movement abnormality that is not uncommon in disorders such as cerebral palsy that can also be seen in certain basal ganglia disorders
~Slow, sinuous, writhing movements
~Continuous mobile spasm
~Most pronounced in fingers, hand and face
Ballismus
~another involuntary movement associated with damage to the basal nuclei- specifically to the subthalamus
~Forceful, flinging movements
~Often rotatory and continuous
~Seen with subthalamic damage which releases movement
Bradykinesia
~Lack of normal movement
~Reduced amplitude of movement
~Many of the symptoms of Parkinson’s disease are the result of this condition
