Basal Ganglia and Internal Capsule Flashcards
function of basal ganglia
fine-tune voluntary movements and are therefore involved in the generation of goal-directed voluntary movements
how do basal ganglia work
- recive info from cerebral cortex
- process and adjust this info
- send it to thalamus
- thalamus sends the adjusted into back to cortex
- the cortex then sends its motor info to the skeletal muscles via the pyramidal system
what are the basal ganglia
a group of subcortical nuclei that from part of the extra pyramidal system
name the five pairs of nuclei that make up the basal ganglia
- caudate nucleus
- putamen
- globus pallidus
- subthalamic nucleus
- substantia nigra
what does the striatum consist of
caudate nucleus and putamen
what does the lentiform nucleus consist of
putamen, globus pallidus and subthalamic nucleus
what is the caudate nucleus part of
striatum
shape of caudate nucleus
c-shaped
made up of head, body and tail
location of caudate nucleus
lateral to lateral ventricles
that does the tail of the caudate nucleus from
roof of inferior horn of lateral ventricles and is terminated by connecting with amygdala
function of caudate nucleus
sends information to thalamus concerning body and limb posture
what is an underactive caudate nucleus linked to
depression and schizophrenia
what is the putamen part of
striatum and lentiform nuclei
shape of putamen
round
location of putamen
medially: globus pallidus
laterally: external capsule
putamen function
regulates motor functions
what is the globus pallidus part of
lentiform nuclei
globus pallidus location
medial to putamen
function of globus pallidus
regulates movements to create smooth and precise actions
substantia nigra location
- small motor nucleus in anterior part of upper mibrain
- functionally part of basal ganglia despite location in midbrain
two components of substantia nigra
pars compacta and pars reticula
what is the dorsal portion of the substantia nigra
pars compacts
what is the pars compacts made up of
dense, dark, melanin-filled neurons
what happens when the dopamine neurons in the pars compacta die
parkinson’s disease
what is the ventral portion of the substantia nigra
pars reticula
pars reticula function
plays a roll in controlling eye movements
what is the internal capsule
mass of white matter which collects all axons beside the thalamus and the third ventricle
function of the internal capsule
large number of motor and sensory fibres travel to and from the cortex via the internal capsule
internal capsule location
bisects basal ganglia
name the three subdivisions of the internal capsule
- anterior limb
- genu
- posterior limb
two types of fibres found in anterior limb of internal capsule
- frontopontine fibres
- thalamocortical fibres
frontopontine fibres
frontal cortex to pons
thalamocortical fibres
thalamus to frontal lobe
what fibres are contained in the genu
corticobulbar fibres
corticobulbar fibres
Cortex to brainstem
what two types of fibres are contained in the posterior limb
- corticospinal fibres
- ascending sensory fibres
corticospinal fibres
cortex to spinal cord
what part of the basal ganglia receive input from the cortex
the striatum
where do the striatum not receive input from
primary visual and auditory cortices
what are the input pathways of the basal ganglia collectively referred to as
corticospinal pathways
where do axons with the striatum synsapse with
- The globus pallidus
- The pars reticula of the substantia nigra (via striatonigral fibres)
describe the output from the basal ganglia to the pars reticula of the substantia nigra
axons synapse with upper motor neurons in the superior colliculus to regulate eye movements
describe output of the basal ganglia to the globus pallidus
axons synapse with the thalamus → thalamus relays this info back to the motor cortex (feedback loop)
name five involuntary movement disorders
- tremor
- athetosis
- chorea
- ballism
- distonia
athetosis
slow involuntary writhing or twisting movements of extremities
chorea
fast or jerky writhing movemets of extremities
ballism
similar to chorea but associated with more proximal extremities such as shoulders and hips
distonia
involuntary contractions of muscles
name five impairments to motion disorders
- akinesia
- bradykinesia
- shuffling gait
- difficulties with speech
- loss of postural reflexes
akinesia
lack of movement
bradykinesia
slowness of movement
causes of parkinson’s disease
- death of dopamine secretion in the substantia nigra
- exact cause is unknown but may be associated with exposure to toxins, historical head trauma, infection and genetics
two treatments for parkinson’s disease
- L-DOPA
- Deep brain stimulation
explain how L-DOPA treats Parkinson’s
its a dopamine precursor that helps alleviate symptoms. its initally effective but after 5-10 years, 50% of patients develop DOPA-induced dykinesia (involuntary erractic movements)
explain how deep brain stimulation trats parkinsons
the activity of the subthalamic nucleus (STN) is increased in parkinsons, high frequency stimulation has been shown to deactivate the STN
cause of huntingtons disease
progressive atrophy of the striatum that is genetic in origin
treatment of huntington’s disease
- xenazine: can supress involuntary movements but has multiple side effects that can cause drowsiness, restlessness and/or psychiatric conditions
- the comorbidity of psychiatric disorders means many patients are treated with antidepressants and antipsychotic drugs
