4.3 - motor pathways pt2 (basal ganglia) Flashcards
components and structures of
- Diencephalon? *4
- Thalamus (all diff thalamic nuclei)
- Hypothalamus (all diff hypothalamic nuclei)
- Epithalamus (pineal gland)
- Subthalamus (part of basal ganglia)
components & struct’s
- Limbic Lobe?
- cingulate gyrus
- uncus & olfactory cortex
- parahippocampal gyrus & hippocampus
- subcallosal gyrus
- septal nuclei
- amygdala
diff btw-
corticospinal vs corticobulbar
- what kind of pathway?
- orig.
- term.
both
Q- what kind of pathway?
A
both direct motor output
both pyramid tracts
Upper motor neurons (UMNs) are the main source of voluntary movement.
Q orig.
A
corticospinal - cortex (homunculas - 1. dorso/lateral precentral gyrus = arm/hand 2. para/central lobule = leg)
corticobulbar - cortex (homunculus - ventral/lateral precentral gyrus)
Q term.
A
corticospinal - term. on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk.
corticobulbar - project to cn. motor nuclei in the brainstem
corticobulbar tract:
is composed of the upper motor neurons of the cranial nerves. The muscles of the face, head and neck are controlled by the corticobulbar system, which terminates on motor neurons within brainstem motor nuclei.
types of HYPERkinetic dyskinesia ? *2
charicterised by?
due to?
- hemiballismus
- huntington’s disease
characterised by
-increased motor activity
due to
-REDUCED inhibition of VENTRAL THALAMUS by
GPi & SNr (vs incr inhib of same for parkinsons)
types of HYPOkinetic dyskinesia ? *1
charicterised by?
due to?
parkinson’s disease
characterised by
- impairment in the initiation of movement
due to
- INCREASED inhib. of ventral thalamus (by GPi & SNr)
damage to the basal ganglia give rise to
disturbances of _ & disorders of _
_disturbance of mus. tone (rigidity)
_disorders of movement (dyskinesias)
hemiballismus:
involuntry
flailing movement of proximal limb
rotatory nature
distal limb movements generally CHOREIFORM
hemiballismus
type of disorder?
due to?
which weakens…?
results in?
symptoms can be reduced by?
hemiballismus is a type of
-hyperkinetic dyskinesia
due to
- vascular leisions
of
-subthalamic nucleus (on the contralateral side of the body)
this weakens
-the influence of the indirect pathway
resulting in
- over excitation of motor cortex
- over exuberance of movement
symptoms can be reduced by
- lesioning the GP & ventral thalamus
hemibalismus
explain disrupted pathway..
due to - loss of output from the subthalamic nucleus (STN) weakens -the indirect pathway making it more difficult to -inhibit unwanted movements
huntington’s disease
explain disrupted pathway
motor impairment
due to
atrophy of the striatum (caudate nucl. + putamen)
reduction of input to the GPe (globus pallidus externus)
weakens both direct and indirect pathway more..
-the indirect pathway
making it more difficult to
-inhibit unwanted movements
&
-causing desired movements to be exuberant
parkinson’s disease
explain the disrupted pathway…
reduced dopaminergic drive from SNc (substantia nigra compacta) weakens - direct pathway making it more difficult to - facilitate desired movement
hemibalismus
basal ganglia effected?
output from STN (subthalamic nucleus)
huntington’s
basal ganglia effected?
red. of input to GPe
parkinson’s
basal ganglia effected?
red. dopaminergic drive from SNc (substantia nigra compacta)
basal ganglia function
mn= file sender
basal ganglia facilitate behavior & movement that are required
and
inhibit inappropriate movents
- search files
- select file, send file to motor cortex
- same time temporary block on unwanted movements
basal ganglia consists of ? *5
- CN (caudate nucleus) -head, body, tail
- Pt (putamen)
- GP (globus pallidus) incl’s GPi & GPe internus & externus
- STN (subthalamic nucleus)
- SNc & SNr (substantia nigra - compacta & reticulata)
basal ganglia
- striatum =
caudate + putamen = striatum
basal ganglia
- lentiform *mn= wifi
putamen + globus pallidus (ext & int) = lentiform
what’s the disease?
inherited autosomal dominant disorder involving progressive dementia and choreiform movements
symptoms appear btw age 30-50
huntington’s disease
whats the disease?
involuntary, flailing movements of the proximal limb, often of roatory nature. Distal limb movements are generally choreiform
Hemiballismus
whats the disease?
bradykinesia (slowness of movement)
akinesia (difficulty initiating movement)
rigidity
tremor
postural instability
masked facies (lack of facial emotion)
involves degeneration of dopaminergic neurons in the SNc (substantia nigra compacta)
which project to the caudate nucleus & putamen
this strengthens the influence of the indirect pathway
The GPi (globus pallidus internus) and the SNr (substantia nigra reticulata) inhibit the
ventral thalamus more strongly
which reduces exitation of motor cortex
and causes poverty of movement
parkinson’s disease
what is?
L-Dopa therapy for parkinsons
effectiveness?
Leva-Dopa therapy provides
-and extra substrate for dopamine production in the remaining SNc (substantia nigra compacta) neurons
effectiveness
wanes as the disease continues to progress
what population has much higher risk of developing
parkinson’s disease?
meth addicts
methamphetamine/ anphetamine overstimulates dopamine production, and withdrawal leads to retarded production (less production of dopamine)
explain deep brain stimulation for parkinsons disease
and implanted electrode that activates the
indirect pathway (GPi & STN subthalamic nucleus)
can dramatically reduce the
-tremors
-rigidity
- and reliance on L-Dopa
