Anatomy: Basal Ganglia Flashcards
Label this transverse section of the cerebrum
What is shown by the additional labels?
What is the basal ganglia?
Basal ganglia refers to a group of subcortical nuclei responsible primarily for motor control:
It lies in the inferior cerebral hemisphere, lateral to the thalamus
Which subcortical nuclei are part of the basal ganglia?
1) caudate nucleus
2) putamen
3) globus pallidus
4) substantia nigra
5) subthalamic nuclei
Amygdala is technically part of the basal ganglia, but functionally is part of the limbic system
Label this, what does it show?
The structures comprising the basal ganglia
Label this coronal section of the brain
All the nuclei in the basal ganglia group together to form…
All the various nuclei in the basal ganglia group together to form corpus striatum, divided into ventral and dorsal
The ventral division= N.accumbens and olfactory tubercule
The dorsal division of the striatum= has the caudate and the lentiform nucleus
Lenitform nucleus is further divided into putamen and globus pallidum
Label the ventral parts of the striatum on this diagram
Draw and describe the structure of the caudate nucleus
What are the relations of the caudate nucleus?
Corpus Callosum lies above the head and body of the caudate nucleus
Thalamus lies medial to most of the caudate nucleus body
Between the thalamus and caudate nucleus, hay the Stria Terminalis and Thalamostriate Vein
The caudate N is separated from Lentiform nucleus by anterior limb of Internal Capsule
Recall that the substantia nigra contain the dorsal Pars compacta and the ventral Pars reticularis.
Where do these send and receive signals from?
Label and describe the subthalamic nucleus
Biconvex shape in subthalamic region at the junction of internal capsule and crus cerebri
Role= integrates and smoothens movements
Functions of the basal ganglia?
Provide a feedback mechanism to the cerebral cortex
Motor refinement: stops unwanted movements, reducing cerebral cortex excitation.
Modulates cognitive + emotional responses through the Ventral striatum which receives limbic inputs
Describe the circuits of the basal ganglia
At least 4 circuits start in the cerebral cortex, cross the Basal Ganglia and return to the cortex:
Motor Loop: learned movements (writing, passing a ball)
Cognitive Loop: motor intentions (prepping for movements)
Limbic Loop: emotional aspects of movement
Oculomotor Loop: Voluntary Saccades
Draw out and describe the direct pathway of the motor loop
+ means excitatory pathway using Glut
- means inhibitory pathway using GABA
Draw out and describe the indirect pathway of the motor loop
How is the substantia nigra involved in both motor loop pathways?
The s.nigra regulates the activity of the corpus striatum of the caudate nucleus and putamen, via fibres which go back and forth from the substantia nigra
The NT is dopamine, which stimulates the direct pathway and inhibits the indirect, thus increasing motor activity.
Draw and describe the limbic loop and how this can link to symptoms of PD
What is huntingtons chorea?
Autosomal dominant
Dopa secreting neurones of SN are overactivated
Nigrostriatal pathway inhibits the caudate nucleus and putamen
CT shows enlarged lateral ventricle due to degeneration of caudate nucleus
