Lecture 18: Basal Ganglia Flashcards
Basal ganglia is a collection of _____ matter nuclei deep within each cerebral hemisphere.
Gray
Basal ganglia receives info from the ______ . It also sends info to the _____ via the _____. Additionally sends info to the _____ directly.
Cerebral cortex.
cerebral cortex
thalamus.
brainstem.
What are four functions of the basal ganglia?
- Important role in higher order control of posture and voluntary movement.
-selecting, reinforcing,
scaling desired motor
output patterns
-initiating and preparation
for movement
-automatic execution of
previously learned
movement patterns - control of eye movements
- cognitive functions
- emotional functions
Define Hyperkinetic movement disorders. Give 1 example.
Uncontrolled involuntary movements which give rise to a random pattern of jerks and twists.
ie. Huntingtons disease
Define Hypokinetic movement disorders. Give 1 example.
Rigidity, slowness of movement, marked difficulty in initiating movements.
ie. Parkingson’s Disease
What 5 components make up the basal ganglia??
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
Which component of basal ganglia follows the contour of the lateral ventricle and lies lateral to thalamus?
Caudate nucleus (C-shaped)
What fuses with the head of caudate anteriorly?
Putamen
Together the caudate and putamen are called the?
Corpus Striatum
In between the putamen and caudate nucleus you can find the _____ joining them.
cellular bridges
What is located medial to the putamen?
Globus pallidus
How many segments of the globus pallidus? Name them.
- The internal and external segments
Together the ____ and ____ are referred to as the ____ nucleus.
Putamen and globus pallidus.
= Lentiform nucleus
Which component is located in the midbrain, just dorsal to basis pedunculi?
Substancia nigra
Substantia nigra has two portions; ventral and dorsal. Name these 2.
Ventral portion: pars reticulata
Dorsal portion: pars compacta
Which portion of the substantia nigra do you find dopamine-containing neurons? (name the portion)
Dorsal portion: pars compacta
What can you find off the caudate nucleus that does NOT belong to the basal ganglia?
Amygdala
Nearly all inputs from other parts of the brain reach the basal ganglia by way of the ____ and ____. (called the ____ ____)
caudate nucleus and putamen. (called the corpus striatum).
All areas of the cerebral cortex have massive projections to corpus striatum called _________.
corticostriatal pathway
What neurotransmitter is used mostly in the corticostriatum pathway?
glutamate
Corticostriatal pathway projections from cerebral cortex to striatum are mostly _____.
excitatory
Besides the corticostriatal pathway another projection to the striatum is the ___ ___ ___ ___ containing dopamine.
substantia nigra pars compacta
Are the substancia nigra pars compacta inputs to striatum excitatory or inhibitory to the striatum?
Both. Excitatory to some cells and inhibitory to other cells in striatum.
Where do the outputs from basal ganglia leave from? (2- be specific)
- internal segment of globus pallidus
2. substantia nigra pars reticulata
Majority of outputs from basal ganglia project to ____ and ____ nuclei of ____.
Ventral lateral (VL) and ventral anterior (VA) nuclei of thalamus.
the outputs sent to the VL and VA of thalamus then project to ____ areas of cortex. Then influence the lateral and anterior ____ tract.
motor.
corticospinal tract
Besides the thalamus outputs of the basal ganglia, where are the other two outputs to? which tracts do they influence?
- Pontomedullary reticular formation - influences descending reticulospinal tract (for automatic posture and gait related movements- anterior motor system pathways)
- Superior colliculus - influence tectospinal tract for coordination of head and eye movements
Basal ganglia influence ___ and ___ motor systems.
lateral and medial
What is the “direct pathway” in the basal ganglia?
From the striatum directly to internal segment of globus pallidus and substantia nigra pars reticulata
What are the 3 functions of the direct pathway?
- serves to release tonic inhibition of the thalamic neurons that project to the cortex (ie. inhibit inhibitory neurons= excitation of thalamus)
- net effect: excitation of thalamus –> greater excitation of motor areas of cortex
- Direct pathway “enhances movement”
What is the indirect pathway in basal ganglia?
From striatum to other basal ganglia nuclei (external segment of globus pallidus and subthalamic nucleus) prior to reaching internal segment of globus pallidus and substantia nigra pars reticulata.
What are the 3 functions of the indirect pathway?
- acts to oppose the dis-inhibitory action of the direct pathway (ie. excite inhibitory neurons in thalamus)
- net effect inhibition of thalamus - decreased excitation of motor areas of cortex
- indirect pathway “diminishes movement”
Motor channel (influences motor control) is the loop from primary motor, _____ and somatosensory cortex –> ______ —> projects to ___ and ___ of thalamus -> to ____ and ______ cortex.
motor association.
basal ganglia.
VL and VA of thalamus.
primary motor cortex and motor association cortex.
Oculomotor channel (for basal ganglia regulation of eye movement) is the loops from posterior parietal and _____ –> ______–>_____ relay nuclei –> to ___ eye fields and ___ eye fields of frontal lobes.
pre-frontal cortex.
basal ganglia.
thalamic relay nuclei.
frontal eye fields and supplementary eye fields of frontal lobes.
Prefrontal channel is the loop from posterior parietal and pre-frontal cortex –> ___–> ______–> to ____ cortex.
basal ganglia.
thalamic relay nuclei.
to prefrontal cortex.
Prefrontal channel is important for? be specific
Important in cognitive processes involving the frontal lobes: planning, working memory, attention and behaviour.
Limbic channel is the loops from limbic cortex –> _____–> _____ nuclei–> outputs relay back to ____.
Basal ganglia.
Thalamic relay.
limbic cortex.
Limbic channel is for?
Regulation of emotions and motivational drives
* likely key role in neuro-behavioural and psychiatric disorders*
What is Parkinson’s disease?
- involves?
- loss of? results in?
- what type of disorder is it?
involves a degeneration of dopamine-containing neurons in substantia nigra pars compacta.
-dopamine normally has a net excitatory effect on thalamus
- loss of dopamine leads to alterations in both direct and indirect pathways of the basal ganglia.
-Results in net decreased excitation of motor cortex –> diminished movement
This leads to Parkinson’s disease which is a HYPOKINETIC movement disorder.
What are the 3 cardinal signs of Parkinson’s disease?
- resting tremors (“pill rolling”) - tremors subside when doing activities but are present at rest
- bradykinesia (generalized slowness in movements)
- muscle rigidity
What are other features of Parkinson’s disease (not cardinal signs)? (12 total… name 6 at least)
- Hypokinesia- decreased amount of movement
- small handwriting (micrographia)
- Akinesia - lack of movement; difficulty initiating movement
- episodes of “freezing” during movement - during change of environment or change in direction of movement.
- masked face, lack of expression - could be due to lack of emotion (changes in limbic channel)
- reduced volume of speech
- postural instability
- Gait- decreased speed, shortened stride, shuffling feet, decreased or absent arm swing
- Festination: difficulty stopping gait once started (CoM forwards therefore hard to stop as trying to catch CoG)
- MSK changes: weakness, decreased muscle strength, joint contractures
- Cardiopulmonary dysfunction
- Swallowing difficulties
What is Huntington’s disease? what type of disorder is it? causes?
Autosomal dominant hereditary disorder. it is a HYPERKINETIC movement disorder
-cause is atrophy of caudate and putamen (corpus stiatum) also association degeneration of cerebral cortex.
Huntington’s disease results in?
reduced inhibition of thalamus and therefore, excessive OUTput from motor cortex.
When does Huntington’s disease get expressed?
Expresses between 40-45 years old. (onset between 40-50) * numbers in notes*
What are the clinical features of Huntington’s disease?
- initial clumsiness, decreased coordination
- generalized chorea
-involuntary, jerky, rapid
movements- tongue protrusion,
facial grimacing
- tongue protrusion,
- personality changes
- depression, psychosis
- cognitive deficits,
dementia
