Cortex and sub-cortical structures

Question 1

Mossy fibres arise from:

Answer 1

1. Spinal cord & convey proprioceptive feedback
2. Pontine nuclei: convey cortical information and copies of motor instructions before they go to the spinal cord
3. Reticular nuclei: receive ascending and descending information Mossy fibres synapse onto granule cells which send up parallel fibres to Purkinje cells

Question 2

Climbing fibres arise from

Answer 2

the inferior olive in brain stem (inputs from cerebral cortex, spinal cord, dorsal column nuclei and red nucleus)

Question 3

Climbing fibre output cell

Answer 3

Inhibitory Purkinje cell

Question 4

What are the 5 nuclei of the basal ganglia?

Answer 4

• Caudate + putamen = striatum
• Globus pallidus (external and internal)
• Subthalamic nucleus
• Substantia nigra

Question 5

Basal ganglia direct pathway:

Answer 5

striatum to GPi/SNr: E from cortex = excitation via disinhibition

Question 6

Basal ganglia indirect pathway:

Answer 6

Indirect pathway: GPe, SThN to GPi/SNr: E from cortex = inhibition

Question 7

How are the excitatory and inhibitory pathways organised ?

Answer 7

Inhibitory pathway has a braking effect on excitation. There’s 2 inhibitory and 1 facilitatory.

Question 8

What happens when there’s dysfunction in direct and indirect pathway?

Answer 8

Dysfunction in Direct = Parkinson’s disease; indirect pathway ballistic disorder such as Huntingdon’s chorea

Question 9

What does the cerebral cortex do?

Answer 9

modulates the action of motor neurones in the brain stem and spinal cord. -> organise complex motor acts + execute fine movements with precision.

Question 10

3 key aspects of cortical structure:

Answer 10

A. Gyri and sulci
B. Thickness
C. Neurones organised in layers and columns

Question 11

What does the supplementary motor area do?

Answer 11

Reciprocal connections with basal ganglia. Important for planning learned sequences of movement; bilaterally active

Question 12

Major input of motor area =

Answer 12

Thalamus

Question 13

Which 2 types of movement heavily rely on motor cortex?

Answer 13

Control of precise stepping movements in visually guided walking

Question 14

Premotor cortex -> inputs and importance?

Answer 14

strong inputs from cerebellum; important for planning visually guided movements: important for bilateral hand movements associated with visual cues from occipital cortex

Question 15

When is cingulate motor area activated?

Answer 15

During imagined movements and signal triggered movements

Question 16

What are the M1 inputs

Answer 16

• Mainly from sensory cortex
• From areas of thalamus which receive inputs from cerebellum
• Some from basal ganglia
• Extensive connections from (and to) other cortical areas

Question 17

What are the M1 outputs

Answer 17

Motor areas in BS, spinal cord via 50% of corticospinal projection neurons One third devoted to the hand