cerebellum & basal ganglia Flashcards
describe the structural anatomy of the cerebellum
-located at the back of the brain and sits in the posterior cranial fossa
-has 2 hemispheres that are connected by the vermis
-high folded surface - folds are called folia to increase SA
-divided into the anterior lobe, posterior lobe and the flocconodular lobe
what are the 3 lobes of the cerebellum?
-anterior
-posterior
-flocconodular lobe
describe the functions of the cerebellum - briefly
- motor coordination - integrates sensory info from body to cooridinate and fine tune movements
-balance & posture control
-motor learning & skill acquisition
how is the cerebellum separated form the temporal and occipital lobes?
by the tentorium cerebelli
describe the grey and white matter of the cerebellum
Grey matter – located on the surface of the cerebellum. It is tightly folded, forming the cerebellar cortex.
White matter – located underneath the cerebellar cortex. Embedded in the white matter are the four cerebellar nuclei
what are the functional divisions of the cerebellum?
-vestibulocerebellum - balance and ocular mvts
-spinocerebellum - coordination of body & limbs
-cerebrocerebellum - plan/execute movements
what are the 3 zones of the cerebellum?
-lateral hemipsheres
-intermediate zone
-vermis
what functional anatomy region would a midline lesion of the cerebellum affect ?
vestibulocerebellum or spinocerbellum
what symptoms would be associated with a midline lesion of the cerebellum (vestibulocerebellum or spinocerebellum)?
-loss of balance
-disturbed gait
-nystagmus (uncontrolled eye mvt)
what functional anatomy zone would a lateral lesion of the cerebellum affect?
-cerebrocerebellum
what symptoms would be associated with a lateral lesion of the cerebellum? (cerebrocerebellum area )
-loss of co-ordination and unsteady gait
-no sensory deficit or muscular weakness
what symptoms would be associated with a bilateral dysfunction eg degeneration of the cerebellum?
-lack of coordination
-intention tremor (rhythmic tremor during a direct and purposeful motor movement)
-unsteady gait
what are the cerebellar tonsils?
they are triangular structures on the posterior lobe
what is an important clinical note about the cerebellar tonsils?
if the intracranial pressure is raised eg during haemorrhage for if there is malformation (congenital) - the cerebellar tonsils can be herniated through the foramen magnum
what 3 paired arteries provide blood supply to the cerebellum?
-Superior cerebellar artery (SCA)
-Anterior inferior cerebellar artery (AICA)
-Posterior inferior cerebellar artery (PICA)
what artery are the superior cerebellar artery (SCA) and the anterior inferior cerebellar artery (AICA) branches of?
the basilar artery
what artery is the posterior inferior cerebellar artery a branch of?
the vertebral artery
what 2 main veins is drainage of the cerebellum done by?
superior and inferior cerebellar veins.
what are the basal ganglia?
a group of subcortical nuclei responsible primarily for motor control, as well as other roles such as motor learning, executive functions and behaviours, pain processing etc
what important neurotransmitter do the BG require to function?
dopamine
what are the input nuclei of the basal ganglia?
-caudate
-putamen
-accumbens
what are the output nuclei of the basal ganglia?
-globus pallidus internal
-substantia nigra pars reticulata
what are the intrinsic nuclei of the basal ganglia?
-External globus pallidus
-Subthalamic nucleus
- Pars compacta of the substantia nigra
what is the function of the basal ganglia?
-motor control - contribute to the initiation, execution and regulation of voluntary mvts - work with cerebral cortex & cerebellum,
-procedural learning - acquiring skills & habits through practice & repetition
-inhibition of unwanted movements
describe the vasculature of the basal ganglia
-comes mainly from the middle cerebral artery (a continuation of the internal carotid artery)
-lenticulostriate arteries - providing vascular supply to the lenticular nucleus and the striatum
what is the striatum?
used to refer collectively to the caudate nucleus, putamen and nucleus accumbens
what are examples of basal ganglia pathologies?
-stroke
-parkinsons disease
-huntingtons disease
-tourette syndrome
-OCD
briefly describe the ‘motor pathways’ to coordinate and control movements in the basal ganglia
-when you want to make a voluntary mvt, the motor cortex sends a signal to the BG
-the BG sends a signal to the thalamus which acts as a relay station
-thalamus sends signal back to the motor cortex which fine tunes the movement instructions
-then motor cortex sends signal to muscles to carry out the movement
what is an example of a hypo kinetic syndrome?
parkinsons disease
what are the clinical features of Parkinsons disease?
-tremors
-bradykinesia -slowness of movement
-rigidity - muscle stiffness or rigidity
-impaired balance and coordination
what systems of the brain does parkinsons disease affect?
-loss of dopaminergic neurons in the substantial nigra pars compact and reduction of levels of dopamine in the striatum
what is Huntington’s disease?
-progressive and inherited neurological disorder that affects movement, cognition, and behavior
-caused by mutation in the HTT gene
what us an example of a hyperkinetic disease & why?
-Huntington’s disease
-this disease is caused by a mutation in the HTT gene and is characterised by involuntary jerky and rapid movements
what structures are impaired in parkinsons disease?
parkinsons is characterised by the degeneration of the dopaminergic neurons in the substantia nigra pars compacta
-this leads to disruptive signalling to the striatum from this structure and leads to bradykinesia etc
describe the structure of the internal capsule as seen on a horizontal section of the hemisphere
- in a horizontal section, the internal capsule is seen as a white matter structure located deep within the brain, separating the basal ganglia and thalamus from the cerebral cortex
-consists of 3 parts - the anterior limb, the genu & the posterior limb
outline the anatomical relations of the internal capsule and the distribution of the motor fibres in relation to the different positions of it
-serves as a major pathway for transmitting sensory and motor information between the cerebral cortex and the brainstem or spinal cord
-anterior limb - fibres are located more medially and include the corticopontine fibres
-genu -corticobulbar motor fibres pass through
-posterior limb -motor fibres are positioned more laterally - the corticospinal tract
briefly describe the motor deficit arising from a stroke in the internal capsule
- it would cause contralateral weakness in muscles
- damage to the motor pathways can result in increased muscle tone & spasticity (ie involuntary contractions)
- loss of motor co-ordination
