basal ganglia

where do the basal ganglia lie?

areas of gray matter deep within white matter of cerebral hemispheres

what is the basic function of the basal ganglia?

provides a feedback mechanism to the motor cortices for initiation and control of voluntary movements

what are 2 other functions of the basal ganglia?

- regulate posture

- assist in learning new motor skills

what are the basal ganglia made up of?

nuclei

what are ganglia?

clusters of cell bodies in the PNS

what are nuclei?

clusters of cell bodies in the CNS

why are basal ganglia better called basal nuclei?

they are clusters of cell bodies within the CNS

what nuclei are the basal ganglia made up of?

- caudate nucleus

- lentiform nucleus:

- putamen

- globus pallidus externus (GPe)

- globus pallidus internus (GPi)

what 2 structures are closely related with basal ganglia?

- substantia nigra

- subthalamic nucleus

what shape is the caudate nucleus?

C-shaped (looking at it anterolaterally)

what are the 3 parts of the caudate nucleus?

- head

- body

- tail

what lies medially to the caudate nucleus?

internal capsule and lateral ventricle

what does the caudate nucleus curve round?

thalamus

what makes up the lentiform nucleus?

- putamen

- globus pallidus externus (GPe)

- globus pallidus internus (GPi)

what separates the 3 components of the lentiform nucleus?

thin sheets of white matter

what separates the caudate and lentiform nucleus?

internal capsule

what separates the lentiform nucleus and thalamus?

internal capsule

what lies medially to the lentiform nucleus?

internal capsule

what lies laterally to the lentiform nucleus?

external capsule

what is the most medial lentiform nucleus?

globus pallidus internus

what is the intermediate lentiform nucleus?

globus pallidus externus

what is the most lateral lentiform nucleus?

putamen

what are the caudate nucleus and putamen collectively known as?

corpus striatum or striatum

what separates the putamen and caudate nucleus?

internal capsule

where is the only point where the putamen and caudate nucleus join?

anteriorly

where does the substantia nigra lie?

between the tegmentum and the crus cerebri

what are the 2 parts of the substantia nigra?

- substantia nigra pars compacta (SNpc)

- substantia nigra pars reticulata (SNpr)

where is the subthalamus located?

- ventral to thalamus

- lateral to hypothalamus

- medial to internal capsule

what does the subthalamus contain?

subthalamic nuclei (STN)

what do the STN do?

assist basal ganglia in regulation of movements

how do the STN assist the basal ganglia?

- receive afferent fibres from GPe

- send efferent fibres to the GPi

what do the basal ganglia influence the motor cortex through?

thalamus

what 2 pathways are there for the basal ganglia to signal the thalamus?

- indirect

- direct

what is constantly happen in the basal ganglia?

globus pallidus constantly sending signals to inhibit the thalamus - preventing unwanted movements

what do the indirect pathways lead to?

inhibition of motor cortex

what does the direct pathway lead to?

excitation of motor cortex

what is the indirect pathway?

information > substantia nigra pc > corpus striatum > GPe > STN > GPi > thalamus > inhibition of motor cortex

how does the globus pallidus cause inhibition of the motor cortex?

increases the inhibitory signals to the thalamus

what is the direct pathway?

information > substantia nigra pc > corpus striatum > GPi > thalamus > stimulation of motor cortex

how does the globus pallidus cause excitation of the motor cortex?

decreases the inhibitory signals to the hypothalamus

why is it important we have the indirect pathway also?

suppresses unwanted muscle contractions to allow for voluntary movements

what neurotransmitter is released from the motor cortex to the corpus striatum?

glutamate - excitatory

what neurotransmitter is released from the corpus striatum to the GPi in the direct pathway?

GABA - inhibitory

what neurotransmitter is released from the GPi to the thalamus?

GABA - inhibitory

what neurotransmitter is released from the corpus striatum to the GPe in the indirect pathway?

GABA - inhibitory

what neurotransmitter is released form the GPe to the subthalamic nucleus in the indirect pathway?

GABA - inhibitory

what neurotransmitter is released from the STN to the substantia nigra in the indirect pathway?

glutamate - excitatory

is dopamine excitatory or inhibitory?

can be both depending on the receptor:

D1 - excitatory

D2 - inhibitory

what neurotransmitter is produced from the substantia nigra pc?

dopamine

what neurotransmitter is produced from the substantia nigra pr?

GABA

what is the hyperdirect pathway?

cortex -> stn -> GPi

what are the pathways called?

nigrostriatal pathway