Lect 13 Neuroanatomy of movements/locomotion I. Flashcards
(37 cards)
1
Q
I. Basics
1. Give some examples of Motor functions?
A
- Activation of learned movement patterns
- Motion planning
- Initiate movement
- Synergies
- Executing a move
- Proprioceptive control of movement
- Modifying (correcting) movement
- Visual and tactile tracking of movement
- Stop movement
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Q
I. Basics
2. What are included in voluntary motor activity?
A
Striated muscles and their innervation
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Q
I. Basics
3. List 2 types of motor systems. Give their characteristics as well!
A
- Central motor system
- thinking about a motor task + planning and setting of parameters of motor response + final command - Peripheral motor system
- execution of purposeful movement
4
Q
II. Peripheral motor system
1. What are the components of peripheral motor system
A
- lower motor neurons (α motor neurons & γ motor neurons)
- motor unit
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Q
II. Peripheral motor system
2. How do we accomplish movements?
A
- lower motor neurons: voluntary movement + reflexes + tone
- axons of lower motor neurons leave the CNS (ventral roots or in motor roots of cranial nerves)
→ neuromuscular junction with striated muscle fibers
6
Q
II. Peripheral motor system
3. what are the characteristics of α motor neurons?
A
- in laminae VIII and IX of ventral horn
- somatotopically organised
- innervation of extrafusal muscle fibres
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Q
II. Peripheral motor system
4. what are the characteristics of γ motor neurons?
A
- muscle tone and maintaining the non-conscious proprioception
- innervation of intrafusal muscle fibers
- are under control of upper motor neurons
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Q
III. What are the main motor pathways?
A
- Corticospinal tract
- Tectospinal tract
- Rubrospinal tract
- Vestibulospinal tract
- Reticulospinal tract
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Q
III. Primary motor cortex
1. What are the Areas where stimulation can trigger a motor response?
A
- Br. 6 (pre- and supplementer motor cortex)
- Br. 8 (FEF)
- Br. 3, 2, 1 (SI)
- Br. 5, 7 (association areas)
- Br. 19 (VII)
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Q
III. Primary motor cortex
2. What are Afferents to primary motor cortex?
A
- thalamus VPL (cutaneous afferent); VPS (proprioceptive info) * cerebellum – thalamus VLp
- basal ganglia – thalamus VLa
- premotor cortex
-> Activity of upper motor neurons is under continuous modulation by sensory signals.
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Q
III. Primary motor cortex
3. What are the Efferents from primary motor cortex?
A
internal pyramidal layer – pyramidal cell axon
* corticospinal tract
* corticonuclear tract (corticomesencephalic, corticobulbar)
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Q
III. Primary motor cortex
3. What are the characteristics of Primary motor cortex: Br. 4?
A
- the neurons of a muscle (group) can be found in several places - plasticity
- learned movements - eliciting movements patterns
- coordination of muscle contractions (synergy)
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Q
IV. Secondary motor cortex (Premotor cortex)
1. What are the roles of Premotor cortex?
A
- planning, execution and preparation of more complicated movements
- activation happens earlier than the motor cortex (prepares it)
- shortens the latency of movement response
- movements and posture comparison with sensory information
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Q
IV. Secondary motor cortex (Premotor cortex)
2. What are the Afferents of premotor cortex?
A
- thalamus VA and VLa (input from striatum) commissural to contralateral premotor
- visual area
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Q
IV. Secondary motor cortex (Premotor cortex)
3. What are the Efferents of premotor cortex?
A
- contributes to the corticospinal tr.
- primary motor cortex
- reticular formation (reticulospinal tr.)
- primary motor cortex
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Q
IV. Secondary motor cortex
4. What is then function of Supplementary motor area: medial part of Br. 6aα and 6αβ?
A
- planning movements, preparing movement patterns
- start movement (speech too!)
- movement related feedback and coordination of movements
- different movement sequences of limbs
- inhibition of mirror movements
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Q
IV. Secondary motor cortex
5. What are afferents of Supplementer motor areas?
A
- from ipsi- and contralateral primary motor cortex, premotor cortex, frontal eye field (reciprocal)
- from thalamus VLa (receives fibers from int. globus pallidus) substantia nigra
- callosal projections from the contralateral supplementary motor cortex
- from thalamus VPS and VPL cutaneous and proprioceptive inf.
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Q
IV. Secondary motor cortex
6. What are Efferents of Supplementer motor areas?
A
- corticospinal tr.– fibers terminate on spinal interneurons, brainstem
- primary motor cortex (str. gran. ext.)
- premotor cortex - str. gran. ext., to contralateral supplementary motor cortex
- reticular formation
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Q
V. What is Somatotopy?
A
“motor homunculus„
a cortical representation of a muscle
(according to how delicate the movements are, not according to muscle mass)
20
Q
VI. List the pyramidal tract
A
CORTICOSPINAL TRACT
CORTICONUCLEAR TRACT
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Q
VI. Pyramidal tract
1A. The role of The corticospinal tracts
A
The corticospinal tracts are not the sole pathways for serving voluntary movements.
-> Rather, they form the pathway that confers speed and agility to voluntary movements and is thus usedr in performing rapid skilled movements.
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Q
VI. Pyramidal tract
1B. Pathway of Corticospinal tracts
A
- The tracts originate from the pyramidal cells (1st neuron) of primary motor cortex Br 4 and secondary motor cortex Br 6.
- The corticospinal fibers pass through the internal capsule, continuing into the brainstem and spinal cord.
- The fibers descend to the pyramidal decussation in the medulla oblongata, where approximately 80% of them cross to the opposite side.
- The fibers continue into the spinal cord where they form the lateral corticospinal tract, which has somatotopic organization: the fibers for the sacral cord are the most lateral, while the fibers for the cervical cord are the most medial. - The remaining 20% of corticospinal fibers continue to descend without crossing, forming the anterior corticospinal tract, which borders the ventral median fissure.
- The anterior corticospinal tract is particularly well developed in the cervical cord, but is not present in the lower thoracic, lumbar or sacral cords.
- The axons of the pyramidal cells terminate via intercalated cells on alpha and gamma motor neurons, Renshaw cells and interneurons (2nd neuron).
- Most fibers of anterior corticospinal tract cross at the segmental level to terminate on the same motor neurons (3rd neuron) as the lateral corticospinal tract.
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Q
VI. Pyramidal tract
2A. The role of Corticonuclear (corticobulbar) tract
A
- Originate from the motor cortex and descend down to cranial nerve nuclei, most importantly the motor cranial nerve nuclei:
- Bilateral for: trigeminal motor nucleus (CN-V), facial motor nucleus (CN-VII, for forehead muscles) and nucleus ambiguus (CN-IX + X)
- Contralateral (crossed) for: abducent motor nucleus (CN-VI), facial motor nucleus (CN-VII, for lower face muscles) and hypoglossal motor nucleus (CN-XII)
- Ipsilateral for: accessory motor nucleus (CN-XI) innervates SCM, a separate spinal nucleus
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Q
VI. Pyramidal tract
2B. The pathway of Corticonuclear (corticobulbar) tract
A
- It is reported to originate mainly from the premotor cortex and to terminate at the pontomedullary reticular formation.
- It innervates axial muscles and the proximal muscles of the extremities; therefore, it is involved in gait function and postural control.
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VII. Extrapyramidal tracts
1. What is the role of extrapyramidal tract?
Unlike the pyramidal tract, which controls conscious, voluntary motor activities, the extrapyramidal motor system (cerebellum, basal ganglia and motor nuclei of the brainstem) is necessary for autonomic and learned motor processes (e.g. walking, running, cycling).
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VII. Extrapyramidal tracts
2A. What is the role of Vestibulospinal tract tract?
- alter muscle tone, extend, and change the position of the limbs and head
- supporting posture and maintaining balance of the body and head
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VII. Extrapyramidal tracts
2A. What is the PATHWAY of Vestibulospinal tract tract?
- 1st neuron: lateral vestibular nucleus
- The tract descends uncrossed through the medulla and through the length of spinal cord in the anterior white column
- The fibers terminate in the anterior grey column by synapsing with internuncial
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VII. Extrapyramidal tracts
2A. What is the PATHWAY of Vestibulospinal tract tract?
- 1st neuron: lateral vestibular nucleus
- The tract descends uncrossed through the medulla and through the length of spinal cord in the anterior white column
- The fibers terminate in the anterior grey column by synapsing with internuncial
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VII. Extrapyramidal tracts
3A. What is the role of Rubrospinal tract?
The tract facilitates the activity of the flexor muscles and inhibits the activity of the extensor or antigravity muscles
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VII. Extrapyramidal tracts
3B. What is the pathway of Rubrospinal tract?
- 1st neuron: red nucleus of the midbrain
- Fibers cross the midline soon after the origin (ventral tegmental decussation)
- The rubrospinal tract descends through the pons and medulla oblongata to enter the lateral white column of spinal cord
- The fibers terminate in the anterior gray column by synapsing with internuncial neurons. (It is an important indirect pathway by which the cerebral cortex and the cerebellum can influence the activity of the alpha and gamma motor neurons of the spinal cord.)
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VII. Extrapyramidal tracts
4A. What is the role of reticulospinal tract?
Throughout the midbrain, pons and medulla oblongata, groups of scattered nerve cells and nerve fibers exist that are collectively known as
the reticular formation.
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VII. Extrapyramidal tracts
4B. What is the pathway of reticulospinal tract?
- 1st neuron: from the pons, these neurons send axons, which are mostly uncrossed, down into the spinal cord and form the pontine reticulospinal tract. From the medulla , similar axons form the medullary reticulospinal tract.
- The fibers descend in the anterior and lateral white column of spinal cord
- The fibers terminate in the anterior gray column and may facilitate or inhibit the activity of the alpha and gamma motor neurons of the spinal cord. By these means, the reticulospinal tracts influence voluntary movements and reflex activity.
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VII. Extrapyramidal tracts
5A. What is the role of Tectospinal tract?
The tract is believed to be concerned with reflex postural movements in response to visual stimuli
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VII. Extrapyramidal tracts
5B. What is the pathway of Tectospinal tract?
- 1st neuron: superior collicles of the midbrain tectumofmidbrain
- Fibers cross the midline soon after the origin (dorsal tegmental decussation)
- The tectospinal tract descends through the anterior white column close to the anterior median fissure
- The majority of the fibers terminates in the anterior gray column in the upper cervical segments by synapsing with internuncial neurons.
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VII. Extrapyramidal tracts
6A. What is the role of Olivospinal tract?
This tract carries proprioception information from muscles and tendons as well as cutaneous impulses to the inferior olivary nuclei, located in the olivary bodies, also known as the olives.
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VII. Extrapyramidal tracts
6B. What is the pathway of Olivospinal tract?
1. neuron
inferior olivary nucleus
2. neuron
spinal cord – cervical segments
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VIII. What is the role of Medial longitudinal fasciculus (MLF)
- Found in the midline of the brainstem
- Arises near the lateral geniculate body
- Mainly a descending tract, but also has some ascending
- Has a lot to do with eye movements and visual information
