Corticobulbar tracts and Basal Ganglia

Question 1

Corticobulbar projections for facial expression above the eyes

Answer 1

Primary motor cortex- bilateral

cranial nerve nuclei- ipsilateral

Question 2

Corticobulbar projections for muscles of facial expression below the eyes, tongue

Answer 2

Primary motor cortex- contralateral

Cranial nerve nuclei- ipsilateral

Question 3

jaw jerk reflex assesses

Answer 3

CN V, its nucleus, and corticobulbar pathway

Question 4

divisions of the facial motor nucleus

Answer 4

medial- bilateral above the eyes

lateral- contralateral below the eyes

Question 5

Cranial nerve VII test shows

Answer 5

cortical lesion- relative preservation of brow and forehead mvmt

facial motor nucleus or nerve lesion: problem wrinkling on side of lesion

Question 6

Cranial nerve XII test

Answer 6

stick out your tong.

Weakness on side of deviation is from primary motor cortex on contralateral side OR nerve on same side.

Question 7

Basal ganglia is responsible for

Answer 7

repeated movement.

It’s called the “accessory motor circuit”

Question 8

lentiform nucleus

Answer 8

putamen + globus pallidus

Question 9

Direct excitation

Answer 9

depolarization –> actioin potential – neurotransmitter release

Question 10

indirect excitation

Answer 10

“disinhibition”

constant hyperpolarization prevents action potentials in an otherwise active circuit

removing the inhibitory action –> “go” (riding the brakes)

Question 11

What is the substantia nigra’s role?

Answer 11

Give that extra push via dopamine (D1 receptors on striatum)- caudate and putamen

Question 12

W/out substantia nigra

Answer 12

bradykinesia, hallmark of parkinson’s

Question 13

parts of substantia nigra

Answer 13

pars compacta

pars reticulata

Question 14

Parts of the striatum

Answer 14

caudate nucleus
nucleus accumbens
putamen

Question 15

Rules to remember for the BG pathways

Answer 15

Basal ganglia structures release GABA
Other structures release glutamate
SN pc releases dopamine

Question 16

2 major pathways by which dopamine turns the basal ganglia ‘on’

Answer 16

Nigrostriatal pathway
Projections from the Substantia Nigra pars compacta to the caudate or putamen
Motor-related

Mesolimbic pathway
Projections form Ventral Tegmental Area to the nucleus accumbens
Limbic

Question 17

2 major fiber pathways reach the thalamus from differnt origins, back to cortex

Answer 17

Ansa lenticularis
– Lens hook

Lenticular Fasciculus
— Lens-like bundle

Thalamic Fasciculus

• – aka Forel’s Field
• – Also carries cerebellar info

Question 18

Parkinson’s Disease

Answer 18

involves a progressive loss of dopamine neurons

Parkinson’s Disease has characteristic motor triad phenotype

Resting tremor
Rigidity (lead pipe)
Bradykinesia (akinesia)

Long-term l-DOPA tx can lead to dyskinesia

A “hypokinetic” disorder
eg. oculomotor hypokinesia

100% of men with REM behavior disorder will develop Parkinson’s Disease

Impulse control deficiencies present later in disease course

Cognitive effects dependent on laterality

Chronic drug abuse (cocaine, amphetamine) linked to higher rates of disease

Question 19

Huntington’s Disease

Answer 19

is another common disorder that targets the Basal ganglia

Huntington’s Disease = genetic mutation of polyglutamine (CAG) repeats causes neuronal death

Targets the striatum
Chorea (random, involuntary, flicking mvmt.)
Considered a disorder of “hyperkinesia”
Indirect pathway is diminished relative to direct pathway

often begins with depression

Question 20

basal ganglia

Answer 20

The basal ganglia connects and extends the function of our reptilian brain to many outputs. It has both motor and non-motor functions integral to carrying out stereotyped and adaptive behaviors.