Motor control pt. 1 Flashcards by Josh Durand

What major areas of the CNS are involved in motor control?

Cerebral cortex
Basal ganglia
Thalamus
Cerebellum
Brain stem
Spinal cord

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What are the 3 divisions of the motor cortex?

Primary motor cortex, premotor area, supplemental motor area.

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What kind of arrangement is the motor cortex made up of? What two areas/functions receive the greatest representation?

Somatotropic arrangement. The hands and speech.

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T/F

+ of a neuron in the motor cortex results in the contraction of a single muscle.

False: stimulation of a neuron in the motor cortex results in gross movement.

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The premotor cortex occupies what aspect(s) of the primary motor cortex? It is below what structure?

The anterior and lateral portions. It lies below the supplemental area.

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The premotor area projects to what 2 areas?

The primary motor cortex, basal ganglia.

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The supplemental motor area lies mainly in what fissure?

The longitudinal fissure

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The supplemental area fxns in concert with the premotor area to carry out what 4 functions?

Attitudinal movements
Fixation movements
Positional movements of head and eyes
Background for finer motor control of arms/hands

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The corticospinal tract originates from 3 major areas, what are they, and how much representation does each area have?

Primary motor cortex (30%)
Premotor and supplemental areas (30%)
Somatic sensory areas (40%)

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The corticospinal tract descends via what structure of the internal capsule?

The posterior limb (between caudate and putamen).

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What part of the medulla is formed by the corticospinal tract?

The pyramids

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Most fibers in the corticospinal tract cross midline and form what? Others stay ipsilateral and form what?

Crossing fibers - lateral corticospinal tract. Ipsilateral fibers - ventral corticospinal tract.

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In spinal preparation, where is the cut and what is the result?

All tracts are cut, separating cord from the brain. Flaccidity (flaccid, floppy paralysis) results.

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In decerebrate preparation, where is the cut and what is the result?

transection at mid-collicular level. Extensors become tonically hyperactive “decerebrate rigidity”.

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In decorticate preparation, what is damaged and what is the result?

Destruction of the cerebral cortex, results in decorticate spacticity.

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Decorticate preparation causes decorticate spasticity due to what phenomenon?

“Release phenomenon”, due to tonic excitation of upper areas of the reticular formation no longer under inhibitory cortical influence.

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Decorticate spasticity is often seen in humans after stroke, on what side?

The hemiplegic side.

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This cause of decorticate spasticity is responsible for 60% of intracerebral hemorrhages.

Rupture/thrombosis of small arteries of the internal arteries.

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This experimental procedure is helpful in the study of reflexes

Decerebration

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In experimental decerebration, what is lost, what is profoundly altered, and what remains intact?

Sensation is lost. Motor control is profoundly altered (b/c descending cortical pathways are interrupted). The brain stem remains intact.

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T/F: in decerebration, activity in some descending pathways become hyperactive?

True

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In decerebration, what reflexes are suppressed, and what reflexes are exaggerated?

Flexion reflexes are suppressed, stretch reflexes are exaggerated (selective excitation of gamma motor neurons).

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T/F: Humans with brainstem damage signs of decerebration have an optimistic prognosis.

False; it’s a poor prognosis in humans.

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What happens initially in spinal shock and why?

Initially all cord functions (including spinal reflexes) are decreased because of the lack of tonic excitation from higher centers.

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T/F: Spinal cord neurons are irreparably damaged after spinal cord transection?

False; these neurons gradually regain excitability (days to weeks).

What is the mass reflex and what causes it?

The mass reflex happens due to transection of the spinal cord. Evacuation of bladder and colon. Flexor spasm.

T/F: the mass reflex happens as the spinal cord becomes excessively active?

True

In spinal shock, what happens to arterial blood pressure and skeletal muscle reflexes integrated in the cord?

ABP falls dramatically, skeletal muscle reflexes integrated in cord are blocked.

The pontine reticular nuclei transmit what kind of signals to what musculature, via what spinal tract?

Excitatory signals to axial trunk and extensor muscles via the medial reticulospinal tract.

The pontine reticular nuclei receive stimulation from what 2 places?

The vestibular and deep cerebellar nuclei.

T/F: the pontine reticular nuclei receive a small degree of natural excitability.

False; they recieve a high degree of natural excitability.

The medullary reticular nuclei transmit what kind of signals, to what musculature, via what spinal tract?

Inhibitory signals to same musculature as pontine reticular nuclei, via the lateral reticulospinal tract.

The medullary reticular nuclei receive strong stimulus from which 3 areas?

The red nucleus, cortex and other motor areas.

T/F: The medullary reticular nuclei only allow for a decrease in tone?

False; they allow for both and increase and decrease in tone.

T/F: The medullary reticular nuclei counterbalance inhibitory signals from the pontine reticular nuclei.

False; they counterbalance excitatory signals from the PRN.

On what does the regulatory actions of medullary reticular nuclei on PRN (increasing or decreasing muscle tone) depend?

The function needed to be performed.

The brainstem is responsible for motor control of which 6 functions?

``` Movement of eyes Respiration Cardiovascular system GI functions Equilibrium Many stereotyped movements ```

What are the 5 descending tracts from brain to SC?

``` Anterior corticospinal tract Lateral corticospinal tract Reticulospinal tracts (medial and lateral often grouped as 1) Vestibulospinal tract Rubrospinal tract Tectospinal tract ```

Which descending spinal tracts are ipsilateral?

Vestibulospinal tract Reticulospinal tracts Ventral corticospinal tract.

Which descending spinal tracts are contralateral?

Tectospinal tract Lateral corticospinal tract Rubrospinal tract

The reticulospinal tract is often considered one, but is actually made up of two tracts. What are they?

Pontine (medial) reticular formation | Medullary (lateral) reticular formation.

The vestibulospinal tracts originate where and stimulate what?

Lateral vestibular nucleus (deiter) to extensor musculature (mainly).

The tectospinal tract innervates what musculature in what way? Where does it originate?

Innervates cervical musculature in orienting reactions. Originates from the superior colliculus.

What tracts make up the lateral motor system of the cord?

``` Lateral corticospinal tract Rubrospinal tract (controls more distal muscles of limbs). ```

What tracts make up the medial motor system of the cord and controls what musculature?

Vestibulospinal tracts Tectospinal tracts Reticulospinal tracts Anterior corticospinal tracts. Controls mainly the axial and girdle muscles.

T/F: the terms medial and lateral refer to where these tracts lie in the cord?

True

T/F: the primary motor cortex maintains a vertical and columnar arrangement?

True

In the primary motor cortex, how many pyramidal cells need to be stimulated to achieve muscle contraction?

50-100

The dynamic output signals from pyramidal cells are excessively excited when to achieve what?

At the onset of muscle contraction to initiate muscle contraction

The static output signals from pyramidal cells fire at a fast or slow rate? What do they maintain?

Slow. They maintain muscle contraction.

What are the 2 phases of voluntary movement?

Planning and program phase | Execution phase

Signals for movements in the planning and program phase of voluntary movement orginate where and sends information where? Via what?

Originate in sensory association cortex, outputs to premotor cortex via basal ganglia and cerebrocerebellum.

Signals for movements in the execution phase of voluntary movement are carried from where to where?

From premotor cortex, to primary motor cortex, to spinal cord (corticospinal projections).

In the execution phase, signals for movements going to the primary motor cortex can also go where?

Spinocerebellum.

In the execution phase, feedback from the periphery travels where?

Spinocerebellum to primary motor cortex.

T/F: It is impossible to separate postural adjustments from voluntary movement?

True

What are the 2 types of postural reflexes provided to maintain a stable postural background for voluntary movement?

Static reflexes (maintain contraction), dynamic short term phasic reflexes (transient movements).

T/F: A major factor of postural control, is with variation in threshold of spinal stretch reflexes.

True

Variation in threshold of spinal stretch reflexes is caused by changes in ____________of motor neurons and changes in _____________ of gamma efferent neurons to ______________.

Excitability. Rate of discharge. Muscle spindles.

What are the 3 types of postural reflexes?

Vestibular Tonic Righting

The vestibular apparatus is an organ that detects what?

Sensations of equilibrium

What are the 3 major components of the vestibular apparatus?

Utricle, saccule, semicircular canals.

T/F: The vestibular apparatus provides information about position and movement of the eyes in space

False; the head.

The vestibular apparatus helps maintain body balance and helps coordinate _______________

movement

In the utricle and saccule what is the sensory area?

The macula.

In the utricle and saccule, what kind of sensitivity causes depolarization/hyperpolarization?

Directional

The utricle and saccule detect orientation of _________ with respect to ___________, and also dectects ____________.

Head, gravity. Linear acceleration.

The macula of the utricle lies in what plane and plays a large role in determining orientation of the head when a person in in what position?

Horizontal plane. Upright.

The macula of the saccule lies in what plane? It plays a major role in determining the orientation of the head when a person is in what position?

Vertical plane. Lying down.

What is the cupula?

In the semicircular canals it is a loose, gelatinous tissue mass that lies on top of the crista.

When are the semicircular canals stimulated? What are they filled with?

When the head begins to rotate. Endolymph.

What is the bilateral orientation of the semicircular canals?

90 degrees to one another (anterior, horizontal, posterior) each set lying the same plane (right anterior - left posterior. Right and left horizontal. Left anterior - right posterior).

As the head begins to rotate, what is the effect on the cupula?

Fluid lags behind and bends the cupula.

As the cupula bends, what neuronal event takes place?

It generates a receptor potential that alters the firing rate in C.N VIII which projects to the vestibular nuclei.

The semicircular canals detect what aspect(s) of rotation?

Acceleration, deceleration.

The semicircular canals are stimulated on which side?

The side of rotation (e.g. right head rotation stimulates right semicircular canal).

Stimulation of semicircular canals is associated with increased _________________ and ________________

Extensor tone. Nystagmus.

Why can issues with the semicircular canals cause nystagmus?

Because they have connection with the vestibular nuclei of C.N VIII which make connection with cranial nerves of eye movement (III,IV,VI), and the cerebellum.

T/F: The fast component (jump ahead to a new focal spot) is initiated by the semicircular canals?

False; fast component stimulated by brain stem nuclei.

T/F: The slow component (tracking) is sometimes initiated by the brain stem nuclei.

False; the slow component (tracking) is initiated by the semicircular canals.

The semicircular canals is thought to have a predictive function which prevents what?

Malequilibrium

What are anticipatory correction attributed to?

Semicircular canals.

The semicircular canals work in close concert with the _____________, especially the _________________

Cerebellum. Flocculonodular lobe.