DLA 23-24 and Lecture 21+22 Flashcards
the embryo of the cerebellum
metencephalic protuberance
general structure of cerebellum
right and left are divided by midline vermis
three lobes separated by two fissures
lateral aspects of the cerebellum
mediate motor activity in the ipsilateral limbs
medial aspects of the cerebellum
mediate motor activity of the trunk
basal ganglia and motor activity
basal ganglia participates in the initiation and control of voluntary movement
receives + input from cerebral cortex
thalamus + input to cortex
basal ganglia - input to thalamus
parts and role of substantia nigra
parts: pars reticulata (SNr) para compacta (SNc)
dopamine released from the pars compacta regulates the function of the basal ganglia
parts of the globus pallidus? (part of basal ganglia)
external lateral part (Gpe/GPL)
internal medial part (Gpi/GPM)
Gpi is the chief output nucleus
Direct and indirect pathway with basal ganglia
direct:
disinhibits the thalamus resulting in the facilitation of movement
uses glutamate and GABA
indirect:
inhibits the thalamus which reduces movement
uses Glutamate and GABA
Direct pathway process
cortex excites the striatum
striatal input inhibits Gpi
increase thalamic activity
indirect pathway process
cortex excites the striatum
striatum inhibits GPe
inhibition of GPe = Sth to be active
Sth excites GPi
GPi excitation leads to inhibiting of the thalamus
less movement
role of dopamine in direct and indirect pathway?
direct pathway:
D1R (excitation)
indirect:
D2R (inhibit)
hypokinesis
slow movement
decreased inhibition of GPi
increased thalamic inhibition
decreased cortical activity
less dopamine released in PD
clinical features of PD
decreased sense of smell
sleep disturbances
autonomic dysfunction
resting tremor
bradykinesia
rigidity
postural instability
neuronal degeneration and HD
degeneration of GABAergic neurons that project to GPe
greater inhibition of Sth
reduced excitation of the GPi
reduced inhibition of thalamus
hyperkinesis = abnormal excessive movement
Hemiballismus
violent flinging and rotary movements of limbs
arises from contralateral Sth injury
increased cortical excitation (reduced GPi)
one-sided hyperkinesia
cerebellar dysfunction
regulates ipsilateral
acute cerebellar damage often yields motor deficits on the same side of the injury
spino cerebellum (anterior lobe)
sensory feedback (trunk and limb movement)
cerebro-cerebellum (posterior lobe)
integrating motor and sensory feedback
precise movements
vestibulo-cerebellum (flocculonodular lobe)
afferents from vestibular apparatus
balance and eye movements
middle and inferior cerebellar peduncle
afferent fibers
superior cerebellar peduncle
efferent fibers
Dorsal spinocerebellar spinal input
ascends ipsilaterally (lower limb) enters the cerebellum via inferior cerebellar peduncle
from golgi tendon
ventral spinocerebellar spinal input
arise from golgi tendon of lower limb (same side)
synapse at posterior horn
enter cerebellum via superior cerebellar peduncle
cuneocerebellar spinal input
upper limb
enter inferior cerebellar peduncle
lesions of spino-cerebellum (anterior lobe)
affect posture and movement of limbs
ataxias of the limbs usually same side (Ipsilateral)
gait ataxia
could be due to malnutrition
cerebro-cerebellum (posterior lobe) lesion
affects accuracy and timing of movements
ataxia decomposition of movement dysarthria dyssynergia (uncoordination of limbs) intention tremor hypotonia
Vestibulo-cerebellum lesion
Nystagmus (ocular ataxia)
tilted head
titubation (head nodding)
wide-based stance
cerebellar tumor
usually astrocytoma or medulloblastoma (embryo)
rare in adults
symptoms of acute intracranial pressure
surgery and chemo is treatment
motor signs of cerebellar tumor
Nystagmus
truncal ataxia
broad stance
hypotonia
cerebellar stroke
potential arteries:
Posterior inferior cerebellar arteries (PICAs)
Anterior inferior cerebellar arteries (AICAs)
Superior cerebellar arteries (SCA)
motor signs:
dysarthria
truncal ataxia
ipsilateral motor signs: dyssynergia intention tremor limb ataxia rebound phenomenon
edema in posterior fossa
malnutrition and the cerebellum
B1 deficiency is linked to the degeneration of the rostral vermis and adjacent parts of the anterior cerebellar lobe
cortical purkinje fibers degenerate
motor signs involve legs and trunk
Louis-Bar syndrome (Ataxia telangiectasia)
autosomal recessive disorder with multiorgan development
neurologic: cerebellar dysfunction degeneration of the purkinje fibers enlarged brain areas (4th ventricle) impaired motor skills
skin and eyes will show small dilated blood vessels
increased vulnerability to radiation and cancer development
