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hbm exam questions > Neuroanatomy of motor systems > Flashcards

Neuroanatomy of motor systems Flashcards

1
Q

Which part of the corticospinal tract would be most likely to be affected by a stroke in the lenticulostriatal arteries.

A

The axons in crus cerebri

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2
Q

Which artery goes around the crus cerebri supplying it with blood?

A

cerebri posterior

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3
Q

Where does the decussation of the pyramidal tract occur?

A

Ventral medulla oblongata

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4
Q

What describes best the exit points for the cranial nerves that handle motor functions of the eyes?

A

Optic nerve medial to crus cerebri dx/sin

Occulomotor inferior to colliculus inferior

Abducens inferior to pons

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5
Q

Several important motor tracts run in the spinal cord. Mention three of them and explain in what part of the spinal cord these different tracts run?

A

Lateral corticospinal tract, dorsal part of the lateral column

Rubrospinal tract, ventral part of the lateral column

Medial corticospinal tract, ventral column

Reticulospinal tract, ventral column

Vestibulospinal tract, ventral column

Tectospinal tract, ventral column

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6
Q

During performance of a voluntary movement two principal basal ganglia pathways are important, the direct and indirect pathways, respectively. For the indirect pathway, which is the effect (i.e. excitatory or inhibitory synaptic output) on the next participating structure. Cerebral cortex to Striatum to Globus pallidus externa to Subthalamic nucleus to Globus pallidus interna to Thalamus to Frontal cortex

A

Cerebral cortex (+) Striatum (-) Globus pallidus externa (-) subthalamic nucleus (+) Globus pallidus interna (-) thalamus (+) Frontal cortex

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7
Q

Which area controls movements guided by visual cues?

A

Dorsal premotor cortex

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8
Q

Which area controls internally generated movement sequences?

A

Supplementary motor cortex

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9
Q

Which area controls a precision grip with the hand?

A

Primary motor cortex (M1)

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10
Q

Which area controls bimanual coordination?

A

Supplementary motor cortex

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11
Q

Where are the axons in the crus cerebri coming from?

A

For instance motor cortex / premotor cortex

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12
Q

The axons coming from crus cerebri will synapse in several locations in the CNS. Give 3 examples and also explain what type of function each of these pathways will perform.

A

Corticospinal – motor information for fine motor control

Corticobulbar – for motor control of facial muscles.

Corticopontine – following a synapse in the pons they will decussate and reach the cerebellum and be involved in motor optimization

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13
Q

What are the major components of a stretch reflex?

A

The pathway can be described as a ‘reflex arc’ which is made up of 5 components:

A receptor – muscle spindle.

An afferent fibre – muscle spindle afferent.

An interneuron – lamina 9 of the spinal cord.

An efferent fibre – α-motoneurones.

An effector – muscle.

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14
Q

What constitutes a motor unit?

A

One motor neuron and all the muscle fibres it innervates.

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15
Q

Describe the stretch reflex pathway and the role of individual elements of this pathway in the motor system.

A
  1. A muscle spindle is suddenly stretched. 2. The signal travels through Ia afferents into the spinal cord. 3. The Ia afferent synapses directly onto the alpha-motor neuron that innervates the same muscle that harbors the muscle in which the stretch occurred. 4. This signal causes the muscle to resist the stretch. 5. Another synapse from the Ia afferents contacts an Ia inhibitory interneuron that inhibits the motor neuron that innervates the antagonistic muscle of the muscle that was stretched. 6. The antagonistic inhibition relaxes the opposing muscle so that it allows for the movement of the agonist muscle.
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16
Q

Describe the sequence of events for executing fast locomotion (running).

A
  1. Motor cortex (Planning)
  2. MLR (mesencephalic locomotor region - initiation)
  3. Brainstem centers (activation of spinal CPGs)
  4. Spinal cord Central pattern Generators (activation)
  5. Recruitment of motor units (first the slow, then the fatigue resistant and final the fast fatigued)
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17
Q

What is true about afferents to the spinal cord?

A) Ia afferents originate from muscle spindles

B) Ib afferents do not originate from Golgi tendon organs

C) Ia afferents do not primarily respond to active muscle contraction

D) Ib afferents do not primarily respond to active muscle contraction

A

A) Ia afferents originate from muscle spindles

C) Ia afferents do not primarily respond to active muscle contraction

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18
Q

Which descending pathway is important for finger movements in the spinal cord?

A

The lateral corticospinal tract is important for finger movements

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19
Q

What is true about the flexion reflex?

A) It is elicited by activation of Ia afferents

B) It is elicited by activation of pain afferents

C) It is monosynaptic

D) It is polysynaptic

A

B) It is elicited by activation of pain afferents

D) It is polysynaptic

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20
Q

What is true about the central pattern generator for locomotion

A) It is activated by the lateral corticospinal tract

B) It is activated by the medial corticospinal tract

C) Its activity is fine tuned by afferents from joint receptors

D) It encodes the precise locomotor pattern and does not need to be tuned

A

C) Its activity is fine tuned by afferents from joint receptors

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21
Q

What is true about the basal ganglia?

A) They contain dopaminergic medium spiny neurons

B) The indirect pathway does not initiate movements

C) Dopamine D1 receptors facilitate the indirect pathway

D) Dopamine D2 receptors facilitate the direct pathway

A

B) The indirect pathway does not initiate movements

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22
Q

What is true about the basal ganglia?

A) Putamen is located posterior to the thalamus

B) Globus pallidus is located medial to putamen

C) The subthalamic nucleus is located rostral to globus pallidus

D) Substantia nigra pars compacta is located rostral to the subthalamic nucleus

A

B) Globus pallidus is located medial to putamen

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23
Q

What is true about the subthalamic nucleus?

A) It is part of the direct pathway

B) It is part of the indirect pathway

C) It plays a role in inhibiting movements

D) It plays a role in facilitating movements

A

B) It is part of the indirect pathway

C) It plays a role in inhibiting movements

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24
Q

What is true about the cerebellum?

A) The cerebrocerebellum receives input from the spinal cord

B) The vestibulocerebellum is important for speech

C) The cerebrocerebellum is important for speech

D) The vestibulocerebellum receives input from the spinal cord

A

C) The cerebrocerebellum is important for speech

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25
Q

What is true about Purkinje cells?

A) They are dopaminergic

B) They receive input from parallel fibers

C) They receive input from climbing fibers

D) They are GABAergic

A

B) They receive input from parallel fibers

C) They receive input from climbing fibers

D) They are GABAergic

26
Q

What is true about cerebellar long-term depression?

A) It takes part in forming declarative memories

B) It depends on calcium

C) It depends on NMDA receptors

D) It depends on metabotropic glutamate receptors

A

B) It depends on calcium

D) It depends on metabotropic glutamate receptors

27
Q

What is true about the primary motor cortex?

A) It is important for postural control

B) It encodes direction of voluntary movements

C) It is important for internally programmed movements

D) It does not take part in learning of motor tasks

A

B) It encodes direction of voluntary movements

28
Q

Which of these cortical regions is particularly important for the generation of sequences of movements?

A) The primary motor cortex

B) The dorsal premotor cortex

C) The supplementary motor area

D) The ventral premotor cortex

A

C) The supplementary motor area

29
Q

Which of these CNS structures play particularly important roles in the control of eye movements?

A) The frontal lobe

B) The parietal lobe

C) Mesencephalon

D) The spinal cord

A

A) The frontal lobe

C) Mesencephalon

30
Q

True/false “Blood to the hand region of M1 is mostly supplied by a. cerebri anterior”

A

False

middle cerebral artery

31
Q

True/false “Nucleus caudatus is located medial to capsula interna”

A

True

32
Q

True/false “The decussation of the pyramidal tract occurs in capsula interna”

A

False

33
Q

True/false “The alpha-motor neurons are located in the ventral horn”

A

True

34
Q

True/false “The superior colliculus is important for eye movements”

A

True

35
Q

True/false “Thalamus is located lateral to capsula Interna”

A

False

36
Q

Explain how motor information is sent to the cerebellum and then back to the cortex. Which white mater tracts are involved and what “relay stations” are involved?

A

Whitematter tracts: corona radiata -> crus cerebri

Cortex -> pons -> cerebellar cortex -> nucleus dentatus -> superior cerebellar peduncle -> thalamus (VLN) -> cortex

37
Q

Which of the following statements about the primary motor cortex are correct?

1) The primary motor cortex (M1) lacks direct projections to the spinal cord.
2) Histologically, M1 is characterized by large pyramidal neurons (Betz cells) in layer V.
3) Surgical removal of M1 impairs postural control, but leaves hand motor skills such as object manipulation virtually intact.
4) M1 is somatotopically organized.

A

2) Histologically, M1 is characterized by large pyramidal neurons (Betz cells) in layer V.
4) M1 is somatotopically organized.

38
Q

In several brain regions, including the ventral premotor cortex, we find an interesting type of neuron which is active both during the performance of an act, and when we watch someone else perform the same act. What are these neurons called?

A

Mirror neurons

39
Q

Many studies, using different methodological approaches, show that the supplementary motor area (SMA) is important for the learning and performance of movement sequences. Please give two examples of research findings that support this notion.

A

Surgical removal of the SMA in the monkey specifically impairs performance and relearning of previously learned sequences.

Human patients with SMA lesions have difficulties performing movement sequences from memory.

Electrophysiological studies in the monkey demonstrate that many neurons in the SMA are specifically active during different phases of sequence performance.

Neuroimaging studies in humans demonstrate that the SMA is activated during sequence performance (and that the activity in this region is related to sequence structure).

40
Q

Which of the following statements about the dorsal premotor cortex (PMD) are correct?

1) The PMD is located on the dorsolateral surface of the precentral gyrus.
2) The PMD plays important roles for sensory guided behaviors, such as reaching for an object or selecting between different behaviors based on sensory cues.
3) The PMD has no connections with M1, nor with the SMA.
4) The PMD is a uniquely human motor area with no counterpart in the monkey.

A

1) The PMD is located on the dorsolateral surface of the precentral gyrus.
2) The PMD plays important roles for sensory guided behaviors, such as reaching for an object or selecting between different behaviors based on sensory cues.

41
Q

The corticospinal tract runs from cortex cerebri to medulla spinalis. Describe how these axons go from the cortex to reach the location of the spinal cord that controls the muscles of the hand. Give the correct anatomical names for the different locations.

A

Cortex -> centrum semiovale (superior corona radiata -> capsula interna (inferior corona radiata) -> crus cerebri -> ventral pons -> medullary pyramids -> most fibers will decussate at the medullary pyramids -> dorsolateral spinal cord -> cervical region of the spinal cord -> ventral horn to control the muscles of the hand.

42
Q

Describe briefly how the axons of the corticospinal tract receive their blood supply.

A

Top-down

  1. Carotis interna (mainly from a. cerebri media)
  2. A. vertebralis and a. basilaris system at crus cerebri
43
Q

What inputs do the deep cerebellar nuclei neurons receive and what are the nature of their connection?

A

Afferent mossy and climbing fibre input (excitatory) and Purkinje input (inhibitory).

44
Q

What inputs do Purkinje neurons receive and what are their connections called?

A

Axodendritic input from granule cells referred to the parallel fibre connection.

Axosomatic input from Inferior olive cells referred to as climbing fibre input.

Local interneurons from Basket, Golgi and Stellate inputs in the cerebellar cortex shape Purkinje activity.

45
Q

Motor learning occurs when an error signal is available, hence an elevated level of the deep cerebellar nuclei activity. Describe how this would be accomplished at the neural level.

A

Weakening of Purkinje activity will lead to less inhibition exerted on DCN output, thus allowing to discharge at higher spiking frequencies.

46
Q

According to a model proposed by Ito and colleagues, inferior olive input to the cerebellum takes the form of a learning signal associated with motor learning? Describe the molecular basis

A
  1. Climbing and parallel fibres simultaneously synapse on Purkinje cells
  2. This trigger AMPA internalization due to:
    * intracellular calcium and activation of second messenger systems (i.e. Phospho-Kinase C (PKC))
  3. This causes LTD on Purkinje neurons and reduce their excitability for as long as 20-30 minutes.

During this period, DCN activity may increase because of reduced inhibition. Without climbing fibre input, DCN are inhibited by P cells, hence low ‘motor learning’ output coming out of the cerebellum to affect cortical activity.

47
Q

What blood vessels supply the motor cortex?

A

a. cerebri anterior (medial) a. cerebri media (lateral)

48
Q

Which neurons give rise to the cortico-spinal tract?

A

Pyramidal neurons

49
Q

In which layer of the motorcortex are Pyramidal neurons located?

A

Layer V

50
Q

What are the histological hallmarks of Pyramidal cells?

A

Pyramidal shape and a large cell body

distinct apical and basal dendrites.

51
Q

True/false “Putamen is located laterally to the internal capsule”

A

True

52
Q

True/false “The crus cerebri is located in the dorsal mesencephalon”

A

False

53
Q

True/false “Nucleus caudatus is located medial to thalamus”

A

False

54
Q

True/false “The corticospinal tract decussates in the pons”

A

False

55
Q

What are the differences between Parkinson’s and Huntington’s diseases? Explain the differences in terms of the behavioral dysfunction and the network organization of the basal ganglia.

A

Parkinson’s disease (PD):

  1. degeneration of dopamine cells in the substantia nigra pars compacta
  2. In PD there is imbalance between the BG direct and indirect pathways in which the direct pathway is weakened in comparison.
  3. The symptoms of PD include rigidity, inability to initiate movements, stiffness, and tremor.

Huntington’s disease (HD):

  1. damage to cortical and striatal neurons.
  2. imbalance causes a weakening of the indirect pathway.
  3. In HD the effects are hyperexcitability, hyperkinesia, involuntary movements and tics.
56
Q

What are common treatments for Parkinson’s disease?

A

Dopamine replacement by L-DOPA. Electrical stimulation (deep brain stimulation).

57
Q

Explain how the brainstem receives blood and how the vessels are located in relation to the brainstem.

A

The vertebral arteries go along the ventral sides of the medulla oblongata.

Where the medulla transitions into pons, the two vertebral arteries join at the midline to form the basal artery.

The basal artery goes along the pons and mesencephalon.

58
Q

Many of the central motor programs are localized to the brainstem-spinal cord level of the CNS. The concept of motor programs, or central pattern generators, is useful when considering how the brain controls our movements. Give a definition of a central motor program, and give also two examples located at the brainstem level.

A

A central motor program is a network of neurons, interconnected so that when the network is activated, a specific output pattern is generated that drives the proper motoneurons to produce a certain motor pattern.

Two examples: The CPG for respiration and the CPG for swallowing are both localized to the brainstem.

Other examples: CPGs for chewing, eye movements.

59
Q

Locomotor movements are controlled by a well-studied central motor program. Indicate where the locomotor program is located, and describe briefly how this was first shown experimentally.

A

The central motor program for locomotion in located in the spinal cord (0.5p). This was shown in experiments on cats, walking on a treadmill belt. After transection of the spinal cord at the lumbar level, i.e. isolating the caudal part of the spinal cord from the rest of the CNS, the hindlimbs (that are innervated from the caudal spinal cord) could still perform well-coordinated rhythmic stepping movements, showing that the CPG for locomotion must be located in the spinal cord

60
Q

Give a brief account of the brainstem mechanisms responsible for the initiation of activity, as well as the level of activity, of the central locomotor program.

A

Initiation:

Mesencephalic Locomotor Region (MLR) is activated (through disinhibition from the Basal Ganglia output nuclei (SNr)). The MLR will then activate the reticulospinal (pontine) descending pathway.

Activity:

The level of activity in the CPG, i.e. the speed of locomotion, is regulated by the frequency of firing in the reticulospinal pathway, - a higher frequency drives the CPG to a higher activity level and faster locomotion.

61
Q

What are the 3 types of motor units?

A
  1. Slow (S) motor units (fatigue resistant) are small, important for sustained muscular contraction (e.g. upright posture)
  2. Fast fatigable (FF) motor units are large, important for brief exertions that require large forces, such as running or jumping.
  3. Fast fatigue-resistant (FR) motor units are of intermediate size, not as fast as FF units. They are substantially more resistant to fatigue and generate about twice the force of a slow motor unit
62
Q

What inhibits Purkinje cell activity?

A

Golgi cells form an inhibitory feedback that may limit the duration of the granule cell input to the Purkinje cells

Basket cells provide lateral inhibition that may focus the spatial distribution of Purkinje cell activity.

hbm exam questions (7 decks)

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