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13g functions of basal ganglia - Coggle Diagram
13g
functions of basal ganglia
Control of voluntary motor activity
Basal ganglia control the voluntary movements, which are initiated by the motor cortex.
During lesions of basal ganglia, the controlling
mechanism is lost and so movements become inaccurate and awkward.
Role of basal ganglia in control of voluntary motor activity includes:
Cognitive control of motor activity,
Timing and scaling of intensity of movements &
Subconscious execution of some movements.
Cognitive control of motor activity.
Physiological studies have shown that neural discharge in basal ganglia,
like cerebellum, begins well before the movements begin.
Therefore, it is believed that basal ganglia, like the cerebellum, are involved in the
planning and programming of the movement.
Most of the motor actions occur as a consequence of thoughts generated in mind.
This process is known as cognitive control of motor activity.
Pathway:
The cognitive control of motor activity is executed by the basal ganglia through the feedback loops (functional neuronal circuit).
The caudate loop is primarily involved in the cognitive control of motor activity.
Timing and scaling of the intensity of movements.
2 important capabilities of brain in controlling the movements are:
Timing
of the movements:
, i.e. how rapidly the movements should be performed and
Scaling
of the intensity of movements:
i.e. how large the movement should be.
In higher animals, the basal ganglia act as important co-ordinating centre
of extrapyramidal system.
In the absence of basal ganglia,
the timing & scaling function becomes very poor.
Subconscious execution of some movements.
Basal ganglia subconsciously execute some movements during the performance of trained motor activities, i.e. skilled activities. Examples
of movements executed subconsciously at the level of basal ganglia are:
Swinging of arm while walking,
Crude movement of facial expression that accompany emotions and
Movements of limbs while swimming.
Control of clutch and brake while driving (constant attention is required
during initial stages; however, they are carried out subconsciously by
basal ganglia as they become routine).
Control of reflex muscular activity
The basal ganglia exert inhibitory effect on spinal reflexes and regulate
activity of muscles, which maintain posture.
Visual and labyrinthine reflexes are important in the maintenance of posture.
The co-ordination and integration of impulses for these activities depend upon basal ganglia.
Control of muscle tone
Muscle spindles and the gamma motor neurons of spinal cord (which are
responsible for maintaining the tone of the muscles) are controlled by
basal ganglia, especially substantia nigra.
Pathway includes projection from cortical inhibitory area-striatum- pallidum-substantia nigra-reticular formation-spinal cord.
Proof:
In lesion of basal ganglia,
muscle tone increases.
Rigidity (lead-pipe type) is a characteristic feature
of Parkinson’s disease.
Role in arousal mechanism
Globus pallidus and
red nucleus are involved in the arousal mechanism
because of their connections with reticular formation.
Extensive lesions in globus pallidus are associated with drowsiness, leading to sleep.