14

Question 1

The basal ganglia receive most of their input
signals from the ………and also return
almost all their output signals back to the ……

Answer 1

cortex

Question 2

The basal ganglia functions

Answer 2

The basal ganglia functions in control of complex motor activity as writing of letters of the
alphabet.

does not function by itself but in close association with
the cerebral cortex. It act as an accessory motor
system

Question 3

The basa l ganglia are formed of:

Answer 3

1-Caudate nucleus.
2-Lenticular nucleus which is formed of: - Putamen (Laterally) - Globus pallidus (medially)
3-Related nuclei.
- Subthalamus
I - Substantia nigra.

Caudate nucleus and Putamen forms the Corpus striatum

Question 4

The afferent connections to the basal ganglia
terminate mainly

Answer 4

in the striatum (Caudate N. & elementor
Putamen).

Question 5

While the efferent connections (outputs)
originate mainly from the

Answer 5

Globus pallidus.

Question 6

The basal ganglia are connected with:

Answer 6

The basal ganglia are connected with:
1- Cerebral cortex by two closed circuits. wind
2- The basal ganglia (internal circuits).
3- The brain stem.

Question 7

1- Connection with the cerebral cortex:

Answer 7

A- Caudate circuit: It is cortico- striato- pallido- thalamo- cortical circuit It has a role in:

Question 8

Connections within the basal ganglia

Answer 8

A- Nigro-striatal dopaminergic pathway:
–From substantia nigra to the striatum (caudate N. and putamen) and secrete the inhibitory neurotransmitter Dopamine.
–It maintains certain degree of inhibition of the striatum.
–Lesion of this pathway leads to Parkinsonism.
B- Striato-nigral and striato-pallidal GABA pathway:
–Fibers from the striatum to substantia nigra and globus pallidus secrete the inhibitory neurotransmitter GABA.
–It maintains certain degree of inhibition of substantia nigra and globus pallidus.
–Lesion in this pathway leads to Huntington’s chorea.

Question 9

Connections with the brain stem:

Answer 9

Fibers from the brain stem to basal ganglia secrete noradrenalin, serotonin & enkephalin.

Output tracts from basal ganglia to brain stem :
•Arise from globus pallidus then pass either through subthalamus or substantia nigra and then project to reticular formation, red nucleus, vestibular nucleus & inferior olivary nucleus
•From them reticulospinal, rubrospinal,vestibulospinal & olivospinal tracts arise and pass to the spinal cord (Constitute a part of extra pyramidal system).

•N.B.:
The proper function of the basal ganglia depends on the balance between the excitatory transmitter (acetylcholine and Noradrenaline) and the inhibitory transmitter (dopamine and GABA).

Question 10

Function of the Basal Ganglia

Answer 10

A-Function of the Basal Ganglia in Executing Patterns of Motor Activity The Putamen Circuit : Control Complex Patterns of Motor activity

B-Role of the Basal Ganglia for Cognitive Control of Sequences of Motor Patterns the Caudate Circuit :

C- Timing and to Scaling the Intensity of Movements
(1) Determine how rapidly the movement is to be performed.
(2)Control how large the movement will be.

D-Functions of Specific Neurotransmitter Substances in the Basal Ganglia

Question 11

Specif ic Neurotransmitter Substances

Answer 11

(1) Dopamine pathways from the substantia nigra to the caudate nucleus and putamen,
(2) Gamma-aminobutyric acid (GABA) pathways from the caudate nucleus and putamen to the globus pallidus and substantia nigra,
(3) Acetylcholine pathways from the cortex to the caudate nucleus and putamen.
(4) Multiple general pathways from the brain stem that secrete norepinephrine, serotonin, enkephalin,
(5) Multiple glutamate pathways that provide most of the excitatory signals that balance out the large numbers of inhibitory signals

Question 12

lesions in The Globus pallidus ?

Answer 12

Athetosis

Question 13

V Lesions of the Substantia nigra?

Answer 13

Parkinsonism

Question 14

lesion in the Subthalamus →

Answer 14

Hemiballismus

Question 15

Multiple small Lesions in the caudate

Answer 15

chorea

Question 16

chorea Characters

Answer 16

–Rapid purposeless involuntary dancing movements during rest.
They are disrupted by voluntary movements.
–Hypotonia: as caudate nucleus is facilitatory to stretch reflex.
Types:
a) Sydenham’s Chorea:
•It is a complication of rheumatic fever.
•It occur 5 – 15 years.
•Common in females than males.
b) Huntington’s chorea:
•Is a heridetary disease.
•Occur in 3rd or 4th decades of life.
•There is spontaneous damage of cholinergic & GABA-neurons in corpus striatum → dementia & chorea

Question 17

Athetosis Characters

Answer 17

Characters:
•Involuntary continuous slow spasmodic writhing snake-like movements of one or more limbs particularly the hands.
•Hypertonia.

Question 18

Hemibalismus

Answer 18

Characters:
•Involuntary sudden strong spasmodic movements involving:
–An arm → pulled upward suddenly with great force.
–A leg → sudden flexion → falling during walking.
•Hypertonia.

Question 19

Parkinson’s disease: (Paralysis Agitans

Cause:

Factors precipitating Parkinsonism:

Pathogenesis:

Answer 19

–Caused by degeneration of dopaminergic neurons in substantia nigra.
–Normally, there is steady loss of dopamine & dopamine receptors with age.

Factors precipitating Parkinsonism:
–Atherosclerosis → ↓ dopamine secretion in corpus striatum.
–Use of tranquilizers → block of dopamine receptors.

Pathogenesis:
–There is imbalance between dopamine (from nigral projection fibers) & acetylcholine (from cortical projection fibers) in corpus striatum.

Question 20

Manifestations of Parkinson’s

Answer 20

Rigidity
b) Tremors : (Static tremors)
c) Akinesia (hypokinesia)

Question 21

Rigidity of Parkinson caused by

Answer 21

Occurs in both flexor & extensor but more in flexors → bending of the body forwards.
Caused by:
a) Loss of supraspinal inhibitory effect of basal ganglia → facilitation of stretc
h reflex → facilitation of γ-motor neurons.
b) Loss of inhibitory effect of substantia nigra on corpus striatum → continuous excitatory output to motor cortex → facilitation of α-motor neurons.
•The rigidity of parkinsonism may be lead-pipe or cog-wheal type while that of UMNL is clasp-knife type due to facilitation of γ-motor neurons only.

Question 22

Tremors of Parkinson

Answer 22

Involuntary, rhythmic, oscillatory movements due to alternating contraction & relaxation of antagonistic muscles (Pill-rolling movement).
•It occurs at a rate of 4-8 cycles/sec.
•Occurs during walking & rest and disappears during sleep or performing voluntary movements (why?)

Question 23

Akinesia of Parkinson

Mechanism

Manifestation

Answer 23

c) Akinesia (hypokinesia)
•Definition: general poverty of movements.
•Mechanism: loss of dopamine secretion → loss of balance between excitatory & inhibitory circuits → difficult initiation & progression of motor activity.
•Manifestation
–Difficulty in initiation of voluntary activities → false paralysis (Paralysis Agitans).
–Loss of subconscious positioning movement of the proximal joints during performance of voluntary motor skillful acts by distal one → positioning must be done voluntarily → more nervous effort to overcome rigidity.
–Mask face: due to lack of automatic facial expressions related to emotions.
–Speech: slow, monotonus & low voume.
–Shuffling gate: patient walks in a short steps without lifting his legs from the ground.