King Ch. 13 - Extrapyramidal system

Question 1

What does the extrapyramidal system refer to?

Answer 1

All descending somatic motor pathways except corticospinal and corticonuclear fibres

It is phylogenetically primitive and found in all but the lowest vertebrates.

Question 2

List the three essential components of the extrapyramidal system.

Answer 2

• Motor command centres
• Spinal pathways
• Feedback circuits

Question 3

How many main motor command centres are in the extrapyramidal system?

Answer 3

Nine

Question 4

Name the motor command centres located in the forebrain.

Answer 4

• Cerebral cortex
• Basal nuclei

Question 5

Name the motor command centres located in the midbrain.

Answer 5

• Midbrain descending reticular formation
• Red nucleus
• Tectum

Question 6

Name the motor command centres located in the hindbrain.

Answer 6

• Pontine motor reticular centres
• Lateral medullary motor reticular centres
• Medial medullary motor reticular centres
• Vestibular nuclei

Question 7

What is the role of the cerebral cortex in the extrapyramidal system?

Answer 7

Controls the descending reticular formation, mainly by inhibition

Question 8

Define the basal nuclei.

Answer 8

A group of telencephalic grey areas, including the caudate nucleus and lentiform nucleus

In this text, the basal nuclei and corpus striatum are regarded as synonymous.

Question 9

What is the primary function of the basal nuclei?

Answer 9

To collaborate with the cerebral cortex via the thalamus

Question 10

Is the midbrain reticular formation also known as?

Answer 10

Mesencephalic reticular formation

Question 11

What do the pontine motor reticular centres primarily affect?

Answer 11

Fusimotor (gamma) neurons

Question 12

What is the function of the lateral medullary motor reticular centres?

Answer 12

Facilitates through disinhibition

Question 13

What is the main influence of the medial medullary motor reticular centres?

Answer 13

Strongly inhibitory on gamma neurons

Question 14

What type of neurons do vestibular nuclei primarily influence?

Answer 14

Extensor alpha (skeletomotor) neurons

Question 15

Name the five extrapyramidal spinal pathways.

Answer 15

• Pontine reticulospinal tract
• Medullary reticulospinal tract
• Rubrospinal tract
• Vestibulospinal tract
• Tectospinal tract

Question 16

Where do the pontine and medullary reticulospinal tracts arise from?

Answer 16

• Pontine motor reticular centres
• Medial medullary motor reticular centres

Question 17

Which tract is well developed in both cats and humans for controlling semi-skilled movements?

Answer 17

Rubrospinal tract

Question 18

What characterizes the vestibulospinal tract?

Answer 18

Does not decussate and projects to extensor skeletomotor neurons

Question 19

What is the role of the tectospinal tract?

Answer 19

Controls reflex movements of the head and neck in response to visual or auditory stimuli

Question 20

Where are the main tracts of the extrapyramidal system located in the spinal cord?

Answer 20

Ventral funiculus

Question 21

How many neurons are there in each extrapyramidal pathway?

Answer 21

Three

Question 22

Which tracts decussate?

Answer 22

• Rubrospinal tract
• Tectospinal tract

Question 23

Which tract does not decussate?

Answer 23

Vestibulospinal tract

Question 24

What type of neuron receives more extrapyramidal projections?

Answer 24

Gamma (fusimotor) neuron

Question 25

Do inhibitory pathways outnumber facilitatory pathways in the extrapyramidal system?

Answer 25

True

Question 26

What type of neurons does the vestibulospinal tract primarily project to?

Answer 26

Alpha (skeletomotor) neurons ## Footnote The vestibulospinal tract is primarily involved in maintaining balance and posture.

Question 27

Which type of neuron receives more extrapyramidal projections?

Answer 27

Gamma (fusimotor) neurons ## Footnote Gamma neurons are crucial for muscle spindle function and regulating muscle tone.

Question 28

What is the role of the gamma (fusimotor) neuron in motor pathways?

Answer 28

Principal link in the motor pathways ## Footnote Gamma neurons modulate the sensitivity of muscle spindles, affecting muscle contractions.

Question 29

Which neuron remains the final common path in motor pathways?

Answer 29

Alpha (skeletomotor) neuron ## Footnote Alpha neurons directly innervate skeletal muscles to produce movement.

Question 30

True or False: Inhibitory pathways dominate the facilitatory pathways in the extrapyramidal system.

Answer 30

True ## Footnote This dominance influences overall motor control and coordination.

Question 31

What is the main inhibitory component of the extrapyramidal system in the spinal cord?

Answer 31

Medullary reticulospinal tract ## Footnote This tract plays a significant role in modulating motor activity and reflexes.

Question 32

How does the extrapyramidal system influence gamma neurons?

Answer 32

Exerts a substantial damping influence ## Footnote This modulation affects muscle tone and reflexes.

Question 33

What is the function of the vestibulospinal tract?

Answer 33

Facilitatory ## Footnote It helps maintain balance and coordinates head and eye movements.

Question 34

Which tracts are presumed to be facilitatory besides the vestibulospinal tract?

Answer 34

Rubrospinal and tectospinal tracts ## Footnote These tracts are involved in motor control and reflexes.