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Neuroscience - Structure and Function of the Human Brain > Chapter 14 - Brain control of movement > Flashcards

Chapter 14 - Brain control of movement Flashcards

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1
Q

Which 3 levels can the central motor system be divided into?

A

Highest: Association areas of neocortex and basal ganglia; strategy.
Middle: Motor cortex and cerebellum; tactics.
Lowest: Brain stem and spinal cord; execution.

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2
Q

What does the highest level of central motor system consist of, and deal with?

A

The highest level consists of association areas of neocortex and basal ganglia.

It figures what the goal of the movement is and the movement strategy that best achieves the goal.

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3
Q

What does the middle level of central motor system consist of, and deal with?

A

It is represented by the motor cortex and cerebellum.

It deals with tactics. It figures out the sequences of muscle contractions, arranged in space and time, required to smoothly and accurately achieve the strategic goal.

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4
Q

What does the lowest level of central motor system consist of, and deal with?

A

It is the brain stem and the spinal cord.

It does execution: activation of the motor neuron and interneuron pools that generate the goal-directed movement annd make any necessary adjustments in posture.

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5
Q

What could the brain be called, seeing as the proper functioning of motor control relies on sensory information?

A

A sensorimotor system.

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6
Q

How does sensory information relate to the 3 levels of movement processing of the nervous system?

A

Highest level: Sensory information generates a mental image of the body and its relationship to the environment.

Middle level: Tactical decisions are based on the memory of sensory information from past movements.

Lowest level: Sensory feedback is used to maintain posture, muscle length, and tension before and after each voluntary movement.

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7
Q

What are the two pathways critical to movement control?

A

The lateral pathway, and the vendromedial pathway.

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8
Q

What is the function of the lateral pathways?

A

They are involved in voluntary movement of the distal musculature and are under direct cortical control.

Cortex -> Lateral pathways.

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9
Q

What is the function of the ventromedial pathways?

A

They are involved in the control of posture and locomotion and are under brain stem control.

Brain stem -> Ventromedial pathways.

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10
Q

What are the 4 ventromedial pathways?

A
  1. Tectospinal tract
  2. Vestibulospinal tract
  3. Pontine reticulospinal tract
  4. Medullary retriculospinal tract
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11
Q

What are the 2 lateral pathways?

A
  1. Corticospinal tract

2. Rubrospinal tract

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12
Q

Describe the size of the corticospinal tract.

A

It originates in the neocortex, and is one of the longest and one of the largest central nervous system tracts. (10^6 axons in humans).

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13
Q

Describe the connections of the corticospinal tract.

A

Two thirds of the axons originate in areas 4 and 6 of the frontal lobe (motor cortex).

Most of the remaining axons derive from the somatosensory areas of the parietal lobe and serve to regulate the flow of somatosensory information to the brain.

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14
Q

Describe the path of the corticospinal tract through the nervous system.

A

MICPBDL

  1. Motor cortex / Somatosensory areas
  2. Internal capsule
  3. Cerebral peduncle
  4. Pons
  5. Base of medulla (Medullary pyramid)
    … DECUSSATION —
  6. Lateral column -> Lateral corticospinal tract
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15
Q

What is the path of the rubrospinal tract?

A
  1. Frontal cortex (same that contributes to corticospinal tract)
  2. Red nucleus
  3. Pons (DECUSSATION)
  4. Lateral column of the spinal cord
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16
Q

What are the effects of lateral pathway lesions?

A
  1. Hinderance of fine movements of arms and hands

2. Slower and less accurate voluntary movement

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17
Q

What do the ventromedial pathways do with sensory information?

A

They use the information about balance, body position, and the visual environment to reflexively maintain balance and body posture.

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18
Q

What are the vestibulospinal and tectospinal tracts’ main function?

A

They keep the head balanced on the shoulders as the body moves through space, and turn the head in response to new sensory stimuli.

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19
Q

What is the path of the vestibulospinal tracts?

A
  1. Vestibular nucleus
  2. Medulla (SPLITTING)
  3. Spinal cord
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20
Q

What is the path of the tectospinal tract?

A
  1. Superior colliculus (Midbrain)
  2. Medulla (DECUSSATION)
  3. Spinal cord
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21
Q

What is the function of the superior colliculus? (Also called “Optic tectum”)

A

It gets input from the retina, and receives projections from the visual cortex and afferent axons carrying somatosensory and auditory information.

From this input, the superior colliculus constructs a map of the world around us.

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22
Q

What is the pontine (medial) reticulorspinal tract’s function?

A

It enhances the antigravity reflexes of the spinal cord. It helps maintain a standing posture by resisting the efgfects of gravity; it does this by facilitating the extensors of the lower limbs.

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23
Q

What is the pontine (medial) reticulorspinal tract’s path?

A
  1. Pontine reticular formation (Pons)
  2. Medulla
  3. Spinal cord
24
Q

What is the medullary (lateral) reticulospinal tract’s function?

A

It liberates the antigravity muscles from reflex control. (This is the opposite of the pontine - medial - reticulospinal tract’s function)

25
Q

What is the medullary (lateral) reticulospinal tract’s path?

A
  1. Medullary reticular formation

2. Spinal cord

26
Q

What is a good memory rule for the pontine and medullary tracts? What is their function?

A

Pontine starts from the pons and goes to the spinal cord.
Medullary starts from the medulla.

Reticulospinal tracts control posture of the trunk and antigravity muscles of the limbs.

27
Q

How does voluntary movement engage the neocortex?

A

The control of voluntary movement engages almost all of the neocortex (not just the cortical areas 4 and 6 / motor cortex).

28
Q

What generates the mental body image of someone’s body position in space?

A

The somatosensory, proprioceptive, and visual inputs to the posterior parietal cortex.

29
Q

What are the two somatotopically organized motor maps in area 6?

A

1: The premotor area (PMA) in a lateral region
2: The supplementary motor area (SMA) in a medial region

30
Q

What areas feed most information to the corticospinal tract?

A

Most of the axons to the CST are contributed by areas 6 and 4.

31
Q

How does area 6 get its information?

A

Prefrontal cortex and parietal cortex both send axons that converge on cortical area 6.

32
Q

What do mirror neurons do?

A

They seem to fire when someone is either performing or observing particular motor acts, such as reaching, grasping, holding, or moving objects.

33
Q

Where does area 6 get the most subcortical input?

Where does it get its input?

What completes the loop?

A

In a nucleus of the dorsal thalamus, called the ventral lateral (VL) nucleus.

This part of VL (VLo), gets input from the basal ganglia deep within the telencephalon.

The basal ganglia gets its input mainly from the frontal, prefrontal, and parietal cortex.

34
Q

What are the main components of the basal ganglia?

A
  1. Caudate nucleus (part 1 of Striatum)
  2. Putamen (part 2 of Striatum)
  3. Globus pallidus
  4. Subthalamic nucleus
  5. Substantia nigra
35
Q

How does information travel in the basal ganglia?

A
  1. Cortex
  2. Striatum
  3. Globus Palldius (GPi)
  4. Ventral lateral nucleus (VLo)
  5. Cortex (SMA)
36
Q

What is the direct motor loop?

A
  1. Excitatory connections from cortex in the putamen
  2. Cells in the putamen make inhibitory synapses on neurons in the globus pallidus
  3. Cells in the globus pallidus make inhibitory connections with cells in Ventral Lateral Nucleus (VLo)
37
Q

What does the direct pathway do in terms of excitation or inhibition?

A

Activation of the direct pathway tends to facilitate the thalamus and information passing through it.

38
Q

What does the indirect pathway tend to do?

A

The activation of the indirect pathway by the cortex tends to inhibit the thalamus.

39
Q

How do the direct and indirect pathways seem to work with each other?

A

The direct pathway may help select certain motor actions, and the indirect pathway may suppress competing and inappropriate motor programs.

40
Q

What are two examples of basal ganglia disorders?

A

Parkinson’s: Substantia Negra neurons degenerate and don’t give dopamine input to Striatum. Hypokinesia.

Huntington’s Disease: Profound loss of neurons in caudate nucleus, putamen, and globus pallidus; additional cell loss in the cerebral cortex and elsewhere. Hyperkinesia.

41
Q

Where does the pathway originate, by which the motor cortex activates lower motor neurons?

A

In cortical layer V.

42
Q

What is the pathway of neurons from the motor cortex towards the spinal cord?

A
  1. Motor cortex (Layer V corticospinal neurons)
  2. Corticospinal tract
    3a. Inhibitory interneurons
    3b. Flexor motor neuron pools
    3c. Motor axons
    3 I. Extendor motor neuron pools
    3 II. Motor axons
43
Q

How does the coding of movement in M1 appear to work?

A

The directions and firing rates of populations of neurons in M1 seem to direct which direction movements go towards and with what force.

44
Q

What does malleability of the motor map mean?

A

Cortical cells in M1 can switch allegiance from participation in one type of movement to another as skills are learned.

45
Q

What is the role of the cerebellum in muscle movement?

A

It calculates a detailed sequence of muscle contractions, each one generating exactly the right amount of force at precisely the right time.

46
Q

Tell a few facts about the anatomy of the cerebellum.

A
  • It has a very high neuron density
  • The cerebellum is divided into 10 lobules
  • Vast majority of the neurons are tiny excitatory neurons called granule cells
  • Largest neuron in the cerebellar cortex is the inhibitory Purkinje cell, which receives E input from granule cellls, and sens I axons to deep cerebellar nuclei
47
Q

What does the vermis in the cerebellum do?

A

It sends output to the brain stem structures that contribute to the ventromedial descending spinal pathways (that control axial musculature).

48
Q

What do the hemispheres in the cerebellum do?

A

They are related to other brain structures that contribute to the lateral pathways, particularly the cerebral cortex.

49
Q

What is the motor loop through the lateral cerebellum?

A
  1. Layer V cells in the sensorimotor cortex
  2. Pontine nuclei (in the pons)
  3. Cerebellum
  4. Ventral lateral nucleus of the thalamus (VLc)
  5. Motor cortex
50
Q

What is the motor loop through the lateral cerebellum important for?

A

It is critical for the proper execution of planned, voluntary, multijoint movements.

It appears to instruct the primary motor cortex with respect to movement direction, timing and force.

51
Q

What can you say about programming the cerebellum?

A

It is important for learning and storing the muscle movements related to new skills; as such, also new motor programs.

52
Q
  1. List the components of the lateral and ventromedial descending spinal pathways. Which type of movement does each path control?
A

Lateral pathways:
1) Rubrospinal tract
2) Corticospinal tract
Controls voluntary movement of the distal musculature.

Ventromedial pathways:
1) Tectospinal tract
2) Vestibulospinal tracts
3) Pontine reticulospinal tract
4) Medullary reticulospinal tract
Controls posture and locomotion.
53
Q
  1. You are a neurologist presented with a patient who has the following symptom: an inability to independently wiggle the toes on the left foot but with all other movements (walking, independent finger movement) apparently intact. You suspect a lesion in the spinal cord. Where?
A

Right side of the lateral column of the spinal cord, at the corticospinal / rubrospinal tracts.

54
Q
  1. PET scans can be used to measure blood flow in the cerebral cortex. What parts of the cortex show increased blood flow when a subject is asked to think about moving her right finger?
A

Supplementary motor area of area 6 of both hemispheres.

55
Q
  1. Why is L-dopa used to treat Parkinson’s disease? How does it act to alleviate the symptoms?
A

Parkinson’s disrupts the function of the SN and causes it to produce less dopamine to the striatum.

L-Dopa boosts DA synthesis in the dopaminergic neurons that are still in SN.

56
Q
  1. Individual Betz cells fire during a fairly broad range of movement directions. How might they work together to command a precise movement?
A

Each cell casts a “vote” for a particular direction of movement. The population of Betz cells then sees which direction corresponds to the most votes (or the average) and movement happens towards that direction.

57
Q
  1. Sketch the motor loop through the cerebellum. What movement disorders result from damage to the cerebellum?
A
  1. Layer V pyramidal cells in the sensorimotor cortex
  2. Pons / pontine nuclei
  3. Cerebellum
  4. Ventral lateral nucleus (Thalamus)
  5. Motor cortex

Movement disorders:
Ataxia (Movements become uncoordinated and inaccurate)
Dyssynergia: Decomposition of synergistic multijoint movement
Dysmetria: Clumsiness like with ethanol intoxication

Neuroscience - Structure and Function of the Human Brain (20 decks)

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