Brain Stems and Motor Sections

Question 1

What does the premotor cortex do?

Answer 1

sets posture at the start of a planned movement; preparation. IT has links with the brain stem and motor cortex

Question 2

Where is the supplementary motor area?

what does the area do?

Answer 2

medial surface of frontal lobe, anterior to the leg area of the PMC.
PLANNING MOVEMENTS, SEQUENCING
If this part of the brain is damaged, complex actions and bimanual coordination are awkward and difficult.

Question 3

what does the primary motor cortex control?

Answer 3

primary motor cortex controls the parameters of the movement (such as rate, force, and direction).

Question 4

explain the CST pathway

Answer 4

fibres from PMC, premotor area, sensory motor cortex -> axons travel through POSTERIOR limb of INTERNAL CAPSULE -> cerebral peduncles of midbrain => basis pontis => medullary pyramids (85% decussate here) = > anterior or lateral funiculus of spinal cord and lateral and anterior CST => ventral horn => ventral root => dorsal rami => spinal nerves => skeletal muscle fibre

directing consciously planned movements of the distal limbs, in particular in controlling complex finger and hand movements.

Question 5

Explain the CBT pathway

Answer 5

UMN’s of cerebral cortex => genu of internal capsule => travel through brainstem with CST, beore exiting tract to innervate LMNs innervating CN nuclei

Question 6

what are the components of the basal ganglia?

Answer 6

Caudate Nucleus
nucleus accumbens
Putamen
Globus Pallidus- exernal and internal
Substantia nigra- pars compacta and pars reticularis
Subthalamic nucleus

Question 7

What components make up the lenticular nucleus?

Answer 7

Putamen

GLobus Pallidus

Question 8

What components make up the striatum?

Answer 8

Caudate nucleus
Nucleus accumbens
Putamen

Question 9

What is hemiballismus and what causes it?

Answer 9

Unilateral destruction of a subthalamic nucleus produces hemiballismus, which is characterised by large scale involuntary movements of the limbs contralateral to the lesion.

Question 10

What causes Parkinsons?

Answer 10

Degeneration of the Substantia Nigra Pars Compacta
characterised by resting tremor, rigidity, and bradykinesia (slowness of movement, particularly difficulty initiating movements).

Question 11

What causes huntingtons?

Answer 11

Degeneration of striatal neurons( Caudate nucleus, nucleus accumbens, putamen) causes Huntington’s disease, resulting in frequent, rapid, brief involuntary movements (chorea), while desired movements are slowed, as well as cognitive decline and emotional changes.

Question 12

What tracts pass through the internal capsule? (7)

Answer 12

Anterior lumb: fibes connecting the thalamus and cingulate gyrus. Frontopontine fibres (frontal lobe -> pons)
Genu: Frontopontine fibres, CBT
Posterior limb: VCBT, somatosensory fibres (medial lemniscus, spinotholamic fibres and fibres from VPM, VPL thalamus —> post central gyrus
reticulenticular: part of the optic radiation (LGN-> calcarine sulcus), corticopontine fibres
Sublenticular: auditory radiation (MGN —> temporal lobe)

Question 13

namea and describe the layers of the cerebral cortex

Answer 13

Layer 1: molecular layer- few neuronal cell bodies, lots of axonsand dendrites
Layer 2: external granular layer- small neurons, engaged in intracortical connections
Layer 3: external pyramidal layer- medium sized neurons whose axons compose commissural and association fibres
Layer 4: internal granular layer - small neruons, site of termination of sensory fibres
Layer 5: internal pyramidal layer- large neurons, origin of fibres to several extracortical organs
Layer 6: polymorphic - large number of fusiform-shaped pyramidal cells, association and projection neurons

Question 14

What do the vermis,
paravermis
and lateral vermis do
(cerebellum)

Answer 14

Midline structures are responsible for the axial (trunk) musculature; more lateral structures are responsible for the limbs.

Question 15

What is the function of the flocculonodular node?

Answer 15

vestibular function - balance

Question 16

What is the function of the inferior cerebellar peduncle?

Answer 16

CONVEYS INPUT:
- from vestibular and reticular nuclei (somatic motor control), most spinocerebellar tracts, inferior olive,

CONVEYS OUTPUT
- from cerebellum to : vestibular and reticular nuclei

Question 17

What is the function of the middle cerebellar peduncle?

Answer 17

INPUT

- from cerebral cortex via pontine nuclei

Question 18

What is the function of the superior cerebellar peduncle?

Answer 18

INPUT
- Ventral spinocerebellar tracts

OUTPUT
- to red nucleus and VA/VL thalamus -> which project to motor areas of the cortex

Question 19

identify the cerebellar nuclei- what are they called?

Answer 19

Fastigial
interposed
DENTATE

Question 20

What are the layers of gray matter in the cerebellum?

Answer 20

Granular layer
Purkinje cell layer
Molecular layer

Question 21

Where do the Purkinje neurons send output too?

What input goes to the PURKINJEs in the cerebellum?

Answer 21

The Purkinje neurons are the output cells of the cerebellar cortex, and they send inhibitory axons to the deep cerebellar nuclei.
Input to the Purkinje cells is either direct (climbing fibres from the inferior olivary nucleus that synapse directly on Purkinje cell dendrites) or indirect (mossy fibres, representing all other inputs, which synapse on granule cells, which in turn send axonal projections through the molecular layer to Purkinje cell dendrites).