Basal Ganglia

Question 1

What is the basal ganglia

Answer 1

The basal ganglia are the scattered masses of
gray matter submerged in the subcortical
substance of the cerebral hemisphere

Question 2

The basal ganglia is part of what system

Answer 2

It is part of the extrapyramidal system which modulates motor activities.

Question 3

Components of the basal Ganglia

Answer 3

Corpus Striatum
Substantia nigra
Subthalamic nucleus of Luys.

Question 4

Where is the corpus striatum located

Answer 4

It is situated at the base of the cerebral hemisphere in close relation to the thalamus.

Question 5

Corpus striatum is divided into two by

Answer 5

Internal capsule.

Question 6

Parts of corpus striatum

Answer 6

Caudate nucleus.
Lenticular nucleus.

Question 7

Caudate nucleus is related to what part of the brain throughout its length

Answer 7

The lateral ventricle of the ventricular system of the brain

Question 8

Caudate nucleus has two portions

Answer 8

A head portion and a tail portion.

Question 9

Caudate nucleus lies where

Answer 9

It lies medial to the internal capsule.

Question 10

Describe the head portion

Answer 10

It bulges into the lateral ventricle and
is situated rostral to the thalamus.

Question 11

Describe the tail portion

Answer 11

The tail is long and arched. It extends along the
dorsolateral surface of the thalamus and ends
in the amygdaloid nucleus.

Question 12

Lenticular nucleus is located where

Answer 12

It is situated lateral to internal capsule

Question 13

What divides the lenticular nucleus into two portions

Answer 13

A vertical plate of white matter called external medullary lamina.

Question 14

What are the two portions of the lenticular nucleus

Answer 14

Outer putamen
Inner globus pullidus

Question 15

Where is substantia nigra located

Answer 15

Below the red nucleus

Question 16

Substantia nigra is made up of

Answer 16

Large pigmented cells( contains high quantity of iron )
Small non pigmented cells

Question 17

Where is subthalamic nucleus of Luys located

Answer 17

It is situated lateral to red nucleus and dorsal or posterior to substantia nigra

Question 18

Next 4 questions will be on connections of the basal ganglia

Answer 18

….

Question 19

How does different components of the corpus striatum on the same side gets connected

Answer 19

They get inter connected by intrinsic fibers

Question 20

What of different components of corpus striatum on each side

Answer 20

They get connected to those of the opposite side by commisural fibers

Question 21

Mention some connections of the basal ganglia

Answer 21

1.Putamen to globus pallidus
2. Caudate nucleus to globus pallidus
3. Caudate nucleus to putamen.

Question 22

List five functions of the basal ganglia

Answer 22

CONTROL OF MUSCLE
TONE.

Control of motor activity

Control of reflex muscular activity.

CONTROL OF AUTOMATIC
ASSOCIATED MOVEMENTS.

Role in Arousal mechanism.

Question 23

How does the basal ganglia control muscle tone

Answer 23

The basal ganglia control the muscle tone.
The gamma motor neurons of spinal cord are responsible for development of tone in the
muscles.
The basal ganglia decrease the muscle tone by inhibiting gamma motor neurons through
descending inhibitory reticular system in the brainstem.

Question 24

During lession of basal ganglia what happens

Answer 24

Muscle tone increases leading to rigidity

Question 25

Three things are involved in control of motor activity what are they

Answer 25

Regulation of voluntary movements Regulation of conscious movements Regulation of unconscious movements

Question 26

Describe how basal ganglia regulate voluntary movement

Answer 26

Movements during voluntary motor activity are initiated by the cerebral cortex. ▣ However, these movements are controlled by the basal ganglia, which are in close association with the cerebral cortex. ▣ The basal ganglia control the motor activities because of the nervous (neuronal) circuits between the basal ganglia and other parts of the brain involved in motor activity. Neuronal circuits arise from three areas of the cerebral cortex: a. Premotor area b. Primary motor area c. Supplementary motor area ▣ All these nerve fibers from the cerebral cortex reach the caudate nucleus. From here, the fibers go to the putamen. ▣ Some of the fibers from the cerebral cortex go directly to the putamen also. The putamen sends fibers to globus pallidus. Fibers from here run towards the thalamus, subthalamic nucleus of Luys and substantia nigra. ▣ The subthalamic nucleus and substantia nigra are in turn, projected into thalamus. ▣ Now, the fibers from the thalamus are projected back into the primary motor area and other two motor areas, i.e. premotor area and supplementary motor area.

Question 27

Describe how basal ganglia regulate conscious movements

Answer 27

Fibers between the cerebral cortex and caudate nucleus are concerned with regulation of conscious movements. ▣ This function of the basal ganglia is also known as the cognitive control of activity. ▣ For example, when a stray dog barks at a man, immediately, the person understands the situation, turns away and starts running.

Question 28

Describe how basal ganglia regulates unconscious movement

Answer 28

Cortical fibers reaching the putamen are directly concerned with regulation of some subconscious movements, which take place during trained motor activities, i.e. skilled activities such as writing the learnt alphabet, paper cutting, nail hammering, etc.

Question 29

How does basal ganglia control reflex muscular activity

Answer 29

The basal ganglia are responsible for the coordination and integration of impulses for reflex activities e.g visual and labyrinthine reflexes which are important in maintaining the posture. During lesion of basal ganglia, the postural movements, especially the visual and labyrinthine reflexes become abnormal. These abnormal movements are associated with rigidity. Rigidity is because of the loss of inhibitory influence from the cerebral cortex on spinal cord via basal ganglia.

Question 30

How does basal ganglia control automatic associated movements

Answer 30

Automatic associated movements are the movements in the body, which take place along with some motor activities. ▣ Examples are the swing of the arms while walking, appropriate facial expressions while talking or doing any work. ▣ The Basal ganglia are responsible for the automatic associated movements.

Question 31

Describe the role of basal ganglia in arousal mechanism

Answer 31

.Globus pallidus and red nucleus are involved in arousal mechanism because of their connections with reticular formation

Question 32

Extensive lesion in globis pullidus cause

Answer 32

Drowsiness leading to sleep

Question 33

List neurotransmitters released by the basal ganglia and their functions

Answer 33

1. Dopamine released by dopaminergic fibers from substantia nigra to corpus striatum (putamen and caudate nucleus: dopaminergic nigrostriatal fibers): deficiency of dopamine leads to parkinsonism 2. Gammaaminobutyric acid (GABA) secreted by intrinsic fibers of corpus striatum and substantia nigra. Acetylcholine released by fibers from cerebral cortex to caudate nucleus and putamen 4. Substance P released by fibers from globus pallidus reaching the substantia nigra 5. Enkephalins released by fibers from globus pallidus reaching substantia nigra 6. Noradrenaline secreted by fibers between basal ganglia and reticular formation 7. Glutamic acid secreted by fibers from subthalamic nucleus to globus pallidus and substantia nigra.

Question 34

Which neurotransmitters are inhibitory fibers

Answer 34

GABA Dopamine