The deep grey nuclei that plan movement before it starts, take their orders from the cortex and hand them back to it through the thalamus. Everything examiners ask comes out of one diagram: the motor loop with its direct and indirect pathways. Expect the parts, connections and functions as a 10- or 15-mark essay, Parkinsonism as a short note almost every year, and one-liners on chorea, athetosis and ballism.
Topics, in the book’s order
- Basal ganglia: circuits and functions · pp. 1082–1085 · asked 7 times
- Parkinson’s and Huntington’s disease · pp. 1085–1086 · asked 11 times
When you’ve read them: Quiz 131 · Basal Ganglia, 15 questions.
After this chapter you should be able to
- name the parts of the basal ganglia, and say what the striatum and the lenticular nucleus are
- list the inputs, the outputs and the connections inside the basal ganglia, and state the motor loop
- trace the direct and the indirect pathway with the sign of every synapse, and explain how each one changes motor output
- explain how the dopaminergic nigrostriatal projection modulates both pathways
- list the functions of the basal ganglia
- explain the cause, features and treatment of Parkinsonism in terms of the circuit
- state the genetic and neuronal abnormality of Huntington’s disease
- define chorea, athetosis and ballism, and name the lesion behind each
Going further: how the basal ganglia contribute to normal motor function as a whole, and the circuit reasoning behind each of their disorders.
Viva checklist
- Name the parts of the basal ganglia
- What is the neostriatum, and what does it do?
- Striatum versus lenticular nucleus
- Inputs to the basal ganglia, and why there is no direct sensory input
- Which part of the striatum does the sensorimotor cortex feed?
- Outputs of the basal ganglia, and the principal output nucleus
- State the motor loop
- Which output is inhibitory and which excitatory?
- The direct and the indirect pathway, with the sign of each synapse
- What does dopamine do to each pathway?
- The nigrostriatal and striatonigral projections, and the disease that follows loss of each
- Striosomes and matrix
- Causes, features and treatment of Parkinsonism
- Why L-dopa and not dopamine? What does deprenyl do?
- Resting tremor versus intention tremor; rigidity versus spasticity
- Cause and features of Huntington’s disease
- Define chorea, athetosis, ballism and hemiballism