BLOCK 3: MPP: (3.2) CNS PHYSIOLOGY & MOTOR CONTROL

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Questions and Answers

What is the primary function of the Supplementary Motor Area?

To inhibit unwanted motor actions

To retrieve and coordinate memorized motor sequences (correct)

To regulate emotional responses during movement

To execute voluntary movements

How does the striatum influence motor control?

Through sensory feedback mechanisms

By directly initiating muscle contractions

As a gateway for commands from the cortex to enter (correct)

By providing excitatory output to the cortex

What is the role of GABAergic neurons in the basal ganglia?

To facilitate sensory input

To provide inhibitory output (correct)

To promote fast muscle contractions

To enhance motor activity

Which structure in the basal ganglia decreases motor activity?

External GP Signup and view all the answers

What is the role of the pars reticulata in motor control?

It contains inhibitory GABAergic neurons Signup and view all the answers

Which structure serves as the hub for all sensory information except olfactory information?

Thalamus Signup and view all the answers

What role do the basal ganglia play in motor control?

They facilitate voluntary motor control by integrating with the cerebral cortex and thalamus. Signup and view all the answers

Which of the following best describes the function of the primary motor cortex?

It plans and executes motor commands by sending signals to muscles. Signup and view all the answers

How do feedback mechanisms in movement primarily operate within the motor control circuits?

By sending sensory information from skin and muscle receptors to inform movement planning. Signup and view all the answers

Which condition is most likely to affect the motor control pathways involving the basal ganglia?

Neurodegenerative diseases such as Parkinson's disease. Signup and view all the answers

What is the interaction between the thalamus and the motor cortex primarily characterized by?

The thalamus serves as a relay station for sensory information that is integrated into motor commands. Signup and view all the answers

Which component of the cerebrum is primarily responsible for high-level cognitive functions such as language and awareness?

Cerebral Cortex Signup and view all the answers

What is the function of the premotor cortex in planning movements?

To develop movement plans based on visual or sensory information. Signup and view all the answers

What role does the IGP play in the direct pathway of the basal ganglia feedback circuit?

It normally suppresses thalamus activity. Signup and view all the answers

Which pathway prevents signaling to the subthalamic nucleus in the basal ganglia?

Indirect pathway Signup and view all the answers

What happens when the striatum is activated in the indirect pathway?

It increases activity in the subthalamic nucleus. Signup and view all the answers

In the feedback circuits involving the basal ganglia, what is the final target of both the direct and indirect pathways?

Thalamus Signup and view all the answers

Which neurotransmitter is predominantly involved in the inhibitory function within the basal ganglia?

GABA Signup and view all the answers

How does Parkinson’s disease affect the feedback circuits in the basal ganglia?

It disrupts dopamine signaling. Signup and view all the answers

What is the main effect of the indirect pathway in terms of motor control?

To act as a brake on direct motor commands. Signup and view all the answers

Which part of the brain provides the primary excitatory signals to the basal ganglia circuits?

Motor Cortex Signup and view all the answers

What is the function of the thalamus within basal ganglia circuits?

To relay motor commands to the cortex. Signup and view all the answers

When the striatum is activated in the direct pathway, what occurs next?

Inhibition of the IGP. Signup and view all the answers

Which of the following conditions is characterized by increased activity in the basal ganglia feedback circuits?

Huntington’s disease Signup and view all the answers

In the context of motor control circuits, what effect does the IGP typically have on the thalamus?

It inhibits the thalamus during motor actions. Signup and view all the answers

Which neurotransmitter is primarily responsible for the excitatory signals within the basal ganglia feedback circuits?

Glutamate Signup and view all the answers

Study Notes

Diencephalon

The diencephalon is a major part of the brain that helps to regulate sensory input, motor output, and hormone secretion.
It connects the cerebrum with the brainstem and spinal cord.
The diencephalon is comprised of two sections: the thalamus and the hypothalamus.

Thalamus

The thalamus is a relay station for all sensory input except for smell.
Sensory information is processed by the thalamus before being sent to the cerebral cortex.
Responsible for allowing consciousness.
Regulates sleep and wakefulness.

Hypothalamus

Regulates basic bodily functions like hunger, thirst, body temperature, and sleep cycles.
It does this by releasing hormones and controlling the pituitary gland.

Cerebrum

The cerebrum is the largest part of the brain and is responsible for higher-level cognitive functions including: * thought, language, awareness, learning, and memory*.

Cerebral Cortex

The cerebral cortex is the outermost layer of the cerebrum.
It’s comprised of four lobes—the frontal lobe, parietal lobe, temporal lobe, and occipital lobe—each of which has a specialized function.*
All sensory, motor, and associative functions occur in the cerebral cortex.

Basal Ganglia

The basal ganglia is a group of nuclei located deep within the cerebrum.
They are responsible for planning and executing movements.
They work with the cerebral cortex and thalamus to control movements.

Planning Voluntary Movement

The primary, premotor, and pars compacta cortex work together to send motor commands to the muscles.
The primary motor cortex is responsible for initiating motor commands.
The premotor cortex plans movements based on sensory input.
The pars compacta sends dopamine to the basal ganglia.

Basal Ganglia Feedback Circuits

The basal ganglia consists of a collection of nuclei that communicate with each other via two pathways: the direct pathway and the indirect pathway.
The direct pathway increases movement by stimulating the thalamus and the motor cortex.
The indirect pathway decreases movement by inhibiting the thalamus and the motor cortex.

Feedback Circuits and Disease States

Parkinson's disease is a neurodegenerative disorder that affects the basal ganglia by inhibiting dopamine production. The result is an inability to initiate movements.
Huntington's disease is another neurodegenerative disorder, this one affects the basal ganglia by damaging the neurons that control movement. The result is uncontrolled and involuntary movements.

Feedback Circuits Explained

The direct pathway begins with the frontal lobe, which sends commands through the striatum to the globus pallidus internal segment (IGP). The IGP is normally inhibiting the thalamus; when it is inhibited by the striatum, it allows the thalamus to stimulate the motor cortex, resulting in movement. Dopamine, which is produced by the substantia nigra, enhances the activity of the direct pathway.
The indirect pathway begins in the frontal lobe, which sends commands to the striatum. The striatum then inhibits the globus pallidus external segment (EGP). The EGP normally inhibits the subthalamic nucleus. The subthalamic nucleus excites the IGP and inhibits the thalamus.
The substantia nigra also produces GABA, which inhibits the direct pathway.

Supplementary Motor Area

The supplementary motor area (SMA) is located in the frontal lobe.
It is responsible for retrieving and coordinating motor sequences to produce learned movements.

Basal Ganglia: Striatum or Neostriatum

The striatum is the primary input structure of the basal ganglia.
It receives signals from the cerebral cortex and sends signals to other parts of the basal ganglia, like the globus pallidus (GP).
The striatum is comprised mainly of GABAergic neurons.

Basal Ganglia: Globus Pallidus (GP)

The GP, the primary output structure of the basal ganglia, is comprised mainly of GABAergic neurons.
The internal GP (IGP) serves to increase motor activity.
The external GP (EGP) serves to decrease motor activity.

Basal Ganglia: Substantia Nigra

The substantia nigra is located in the midbrain.
It is comprised of a group of dopamine-producing neurons that project to the basal ganglia.
It also contains GABAergic neurons.
The substantia nigra is essential for regulating movement and motivation.
Neurons from the pars reticulata in the substantia nigra send inhibitory signals to the thalamus.

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Description

Explore the complex functions of the diencephalon and cerebrum in this quiz. Learn about the roles of the thalamus and hypothalamus in sensory processing and hormone regulation, as well as the higher cognitive functions governed by the cerebrum. Test your knowledge on these crucial brain components.