Basal ganglia Flashcards
where is the basal ganglia derived?
Telencephalon, with the cortex
What is the basal ganglia?
Group of subcortical nuclei, grey matter
Outline the basal ganglia
Subthalamic nuceli
Substantia niagra- pars compacta and pars reticulata
Corpus striatum- caudate nucleus and lentiform- putamen and globus pallidum
Name the 4 loops the basal ganglia is involved in
Motor- premotor cortex
Occulomotor
Cognitive
Limbic- cingulate cortex- emotion
Where does the corpus striatum receive info from?
Cortex
How does the basal ganglia feedback to the cortex?
Ventral lateral and ventral anterior nucleus of the thalamus
Describe the position of the caudate and lentiform nucleus
Caudate- medial, follows lateral ventricle
Lentiform- lateral, wedge shaped
What is the main function of the basal ganglia?
To refine movement
Name the three main neurotransmitters?
Dopamine- excitatory
Glutamate- excitatory
GABA- inhibitory
Name the function of the direct pathway
and describe the pathway
DRIVE MOVEMENT Cortex Striatum Internus (GP) Thalamus
Name the function of the indirect pathway and describe it Could stop Get externus Then Into Thalamus
INHIBIT MOVEMENT Cortex Striatum GP externa subThalamic nuclei GP Internus Thalamus
Basal ganglia circuitry
Direct pathway- decide to move cortex sends glutamergic excitatory input to striatum. This sends GABA inhibitory input to the GP interna and substantia niagra which sends less GABA to the thalamus (inhibits inhibition), which sends glutamate to the cortex.
Indirect pathway- cortex sends glutamate to striatum, GABA to GP externa, inhibits inhibition of subthalamic nucleus, sends glutamate to GP internus and SNPR, activates inhibition of the thalamus.
How is dopamine involved in basal ganglia circuitry?
The substance nigra releases dopamine which bind to D1 receptors in the striatum to excite the direct pathway and D2 receptors to inhibit the indirect pathway
What are the 5 functions of the cerebellum?
- Synchronise activity between muscle groups
- Balance
- Co ordination
- Posture
- Smooth movement
What does the cerebellum not do?
Initiate movement
Where is the cerebellum derived from?
Metencephalon- hind brain
What is cerebellar ataxia?
Ataxia- loss of control of movement
Symptoms- Slurred speech, bad posture, nystagmus (uncontrolled eye movement)
Causes- stroke, tumours, trauma
Where is the cerebellum located?
Posterior to pons
Inferior to temporal and occipital lobes
Name the three lobes of the cerebellum
Anterior lobe, posterior lobe, flocculonodular lobe
Ant and post sep by primary fissure
Post and flocculonodular sep by posterolateral fissure
What is the function of the cerebellar peduncles?
Sup- connects to midbrain
Mid- pons
Inf- medulla
List the three main components of the cerebellar cortex
Molecular- cont axons of gran, dendrites of purk
Purkinjie- major output, dendrites that fan out
Granular- granule cells, major input
Describe the features of climbing fibres
1: 1
- Inferior olivary nucleus- on medulla
- lateral to pyramids
- 1 climbing fibre activates 1 purkinjie cell
Describe the features of mossy fibres
1 mossy fibre activates 100s of granular cells
1 granular cell activates 1000s of Purkinjie cells
originate in SC and BS nuclei
form small processes- rosettes
both become demyelinated in the granular layer- grey matter
List the 3 functional zones of the cerebellum
Spinocerebellum- vermis and intermediate zones
Vestibulocerebellum- flocculonodular lobe
Cerebrocerebellum- lateral hemispheres
Name the input and function of the vestibulocerebellum
Input: Ipsilateral
Function: balance/eye movement
Name the input and function of the spinocerebellum
Input: ipsilateral, from periphery
Function: proprioception, anticipate movement
Name the input and function of the cerebrocerebellum
Input: contralateral from cortex
Function: plan movement, time action
Describe the vestibulospinal tract
Vestibulocerebellem receives info from the vestibular nuclei via ICP, ICP send info to fastigial nucleus. Input from inner ear via CN8.
Describe the reticulospinal tract
Fastigial nucleus sends info to reticular formation via ICP. Interposed nucleus sends info to reticular formation
Describe the rubrospinal tract
Interposed nucleus sends info via SCP to the red nucleus. Dentate nucleus inputs from the cerebrocerebellum- rubrospinal tract
Dentate nucleus sends info to thalamus via SCP– cortex–pontine nucleus–MCP
