Question

Arrange the events during basal ganglia functioning in the correct sequence:

a) Disinhibition of thalamic nuclei → Inhibition of globus pallidus → Excitation of corpus striatum
b) Inhibition of globus pallidus → Excitation of corpus striatum → Disinhibition of thalamic nuclei
c) Excitation of corpus striatum → Disinhibition of thalamic nuclei → Inhibition of globus pallidus
d) Inhibition of globus pallidus → Disinhibition of thalamic nuclei → Excitation of corpus striatum

Answer 1

The correct sequence of basal ganglia functioning involves the excitation of the corpus striatum, followed by inhibition of the globus pallidus, and subsequently the disinhibition of the thalamic nuclei.

Step-by-step explanation:

The correct sequence of events during basal ganglia functioning is covered by the direct pathway of the basal nuclei. Initially, there is excitation of the corpus striatum by inputs from the cerebral cortex. This excitation is an excitatory connection releasing glutamate as a neurotransmitter to the striatum (caudate and putamen). Next, the striatum projects inhibitory signals to the globus pallidus internal segment (GPi) and the substantia nigra pars reticulata (SNr), which releases GABA at synapses, resulting in the hyperpolarization of these target cells. This inhibition leads to the disinhibition of the thalamic nuclei, meaning the usual inhibition on the thalamus by the GPi/SNr is lifted, allowing the thalamus to excite the cortex and increase motor activity. Thus, the correct sequence is:

1. Excitation of corpus striatum
2. Inhibition of globus pallidus
3. Disinhibition of thalamic nuclei