Chapter 5 Flashcards
basal ganglia located all over the brain but all have one thing in common
- prepare the starting and stopping of voluntary motions, by means of direct and indirect pathways for motor movements
- work together
major components of basal ganglia
- caudate and putamen (striatum)
- globus pallidus
- subthalamic nucleus
- substantia nigra
- nucleus accumbens
basal ganglia striatum
caudate nucleus and putamen
direct pathways for motor movements in the basal ganglia
implicated in functions concerned with the initiation (or excitation) of motor movements
indirect pathways for motor movements in the basal ganglia
implicated in the stopping (or inhibition) of motor movements
movement disorders (basal ganglia disorders) classified into two broad categories
hyperkinetic disorders and hypokinetic disorders
hyperkinetic disorders
when the excitatory pathways become overactive relative to the inhibitory pathways
hypokinetic disorders
when the inhibitory pathways become overactive relative to the excitatory pathways
substantia nigra divided into two parts
pars compacta (SNc) and pars reticulata (SNr)
pars compacta (SNc) of the substantia nigra
source to one of the major domaince projections, the nigrostriatal pathway (from SNc to neostriatum)
pars reticulata (SNr) of the substantia nigra
mostly GABA (inhibitory) neurons to thalamus
dopamine
excitatory
GABA
inhibitory
Parkinson’s Disease
- movement disorder
- results from the degeneration of the pars compacta neurons
- characterized by: muscle rigidity, bradykinesia/akinesia, resting tremor
- most common treatment is replacement therapy with L-DOPA, a precursor of dopamine
- can treat by lesioning part of the pars compacta (SNc) to reduce inhibition of dopamine
hypokinetic disorder
Parkinson’s disease
stages of progression of physical signs of Parkinson’s disease
- stage 1: unilateral movement; early masking of facial expression, affected arm in semiflexed position with tremor
- stage 2: bilateral involvement with early postural changes; slow, shuffling gait with decreased excursion of legs
- stage 3: pronounced gait disturbances and moderate generalized disability; postural instability with tendency to fall
hyperkinetic disorders
- Huntington’s disease
- Hemiballismus
- Athetosis
nigrostriatal pathway
from the substantia nigra in the midbrain, dopamine, to the caudate/putamen (straitum)
- initiate movement
reverse of nigrostriatal pathway
from the caudate/putamen (striatum), GABA, to the substantia nigra
- stop movement
Huntington’s Chorea
symptoms include:
- involuntary jerking or fidgety movements of the limbs and body
- stumbling and clumsiness
- cognitive impairment: difficulty planning and determining the direction of movement
- emotional and motivational issues: difficulty controlling the emotional and motivational aspects of movement
- no caudate, so no GABA –> over-movement
Hemiballismus
- onset can occur at any age and always due to stroke
- damage in subthalamic nucleus (STN) or globus pallidus (GPc)
- severe contralateral flinging movements (arms or legs)
