Motor Systems Flashcards by Emilia McColm

Which regions of the cortex are involved in motor control?

All of the frontal lobe

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What happens to the cortical region’s role in movement as you move more and more anatomically anterior?

It becomes more and more complex and abstract.

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What is area 4?

What anatomical landmark is it immediately anterior to?

Primary motor cortex - the lowest level of motor hierarchy

Central sulcus

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What do local lesions to area 4 cause?

Paralysis or paresis of specific muscle groups

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What do strokes involving occlusion of the middle cerebral artery affect? Is the effect contra or ipsilateral?

Almost all of one side of the frontal lobe
They produce severe motor disability in all parts of the contralateral body (except the lower limb as this region of motor cortex is supplied by anterior cerebral artery).

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Which is more severe - blockage of M1 or M3 (parts of the MCA)? Why?

Blockage of M1, as it is more proximal and affects the blood supply to the basal ganglia (via the lenticulostriate arteries) as well as the blood supply to the motor cortex.

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What is area 6? What is area 8?

Premotor cortex

Supplementary motor cortex

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Damage to areas 6 and 8 leads to what clinical syndrome? Explain this syndrome.

Apraxia.

Patients with apraxia have normal reflexes and no muscle weakness but have difficulty performing complex motor tasks.

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What else can damage to areas 6 and 8 cause?

Does damage to one side produce mild or severe symptoms? Why?

Lesions of this cortex may also impair motor responses to visual or other sensory cues.
Only minimal symptoms - the contralateral area may be able to take over some functions.

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Frontal eye fields and Broca’s area are adjacent to what area?
What two special motor systems do they control?

Premotor area

Extraocular eye muscles and the muscles regulating speech

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What does damage to Broca’s area lead to?

Motor aphasia - patient has difficulty verbalising word strings such as complex sentences.

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What is oculomotor apraxia?

How do patients compensate?

Patients have difficulty moving their eyes horizontally and moving them quickly to follow a moving object, due to problems with the programmes controlling voluntary eye movements.
Patients have to turn their head in order to compensate.

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What is one cause of oculomotor apraxia?

Bilateral lesions of the frontal eye fields

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Frontal eye fields control…

Voluntary eye movements

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What does saccade mean?

Rapid eye movements between fixation points.

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What 3 areas contain the somatosensory cortex? Where does this lie?

Areas 1, 2 and 3 (parietal lobe)

Immediately posterior to the central sulcus

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How many % of the corticobulbospinal tract arises from the somatosensory cortex?
What do these axons do?

40%

They send commands down to the spinal cord that modulate sensory input and they can modulate reflexes.

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What are areas 9 and 10? What do they do?

Dorsolateral pre-frontal cortex

Planning of movement - we evaluate different possible future actions and decide which is best (executive functions).

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Which areas have the most complex relationship with movement?

Areas 9 and 10

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What does a dorsolateral frontal lesion cause? (4)

Apathy
Personality changes
Lack of ability to plan
Poor memory for verbal (left hemisphere) or spatial (right) information

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What is a common test for frontal lobe function?

Wisconsin card sorting test

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What cortex is commonly damaged by road traffic accidents/blows to the head that cause contusions?

Frontal cortex (impact with frontal bone)

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What is area 11?

Orbitofrontal cortex

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What is the orbitofrontal cortex concerned with?

Control/inhibition of motor responses associated with the limbic system - e.g. hunger, thirst, sexual drive

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What type of behaviour is caused by orbital damage?

Pseudo-psychopathic (due to disinhibition)/acquired sociopathy = ORBITAL PERSONALITY

What does puerile mean?

Childish, silly, immature

Which areas feed into the corticobulbospinal tract? (5)

``` Areas 1, 2 and 3 Area 4 Areas 6 and 8 Frontal eye fields Broca's ```

Which areas feed into areas 6 and 8? (2)

Area 9 and 10 | Area 11

What area does 6 and 8 feed into?

Area 4 - primary motor cortex

What do both the basal ganglia and cerebellum project on to (route for motor commands)? Motor thalamus projects onto...?

``` Motor thalamus (VL thalamic nucleus) Motor cortex ```

The corticobulbospinal tract courses through what structure on its way to the brainstem? What is it especially vulnerable to damage by here?

Internal capsule | Stroke

What are the two components of the corticobulbospinal tract?

Corticobulbar | Corticospinal

Where does the corticobulbar component terminate? (4)

Cranial nerve nuclei (for control of muscles of head and neck) Cells of pontine nuclei Reticular formation Red nucleus (in midbrain, next to oculomotor nuclei)

Where does the corticospinal component decussate? | What two tracts does it form?

Lower medulla | Large lateral and small anterior corticospinal tracts

Where does motor decussation occur? What level?

Upper spinal cord (C1-C5)

If the brain is injured above the spinal cord, on what side is the motor deficit?

Opposite side

If the spinal cord is injured, on what side is the motor deficit?

Same side

The lateral corticospinal tract is in the ____ quadrant of the cord, near the motor neurons supplying the _____ muscles.

Dorsal | Distal

What is the only place the corticospinal tract has mono-synaptic connections with? What are the motor actions in other muscles mediated by?

Thumb and digits | Spinal inter-neurons

Where does the anterior corticospinal tract terminate? | What does it control?

Cervical cord. | It controls voluntary movements of the neck.

Damage to the corticospinal tract in the spinal cord causes loss of control of hands and fingers, but NOT...

Loss of posture or locomotion and gait (mediated by extra-pyramidal systems)

What are the main components of the extra-pyramidal system? (2)

Lateral vestibulospinal tract | Reticulospinal tract

Lateral vestibulospinal tract - where does it originate? What does it control? (IPSILATERAL)

Vestibular nuclei in upper medulla/lower pons | Posture and balance - anti-gravity muscles

Reticulospinal tract - where does it arise? What is it responsible for? (3) (BILATERAL)

Reticular formation of pons and medulla Autonomic control (sympathetic preganglionic neurones) Drive to respiration (phrenic nerve) General ‘arousal’ of spinal cord

Rubrospinal tract - where does it originate? What does it carry?

Red nucleus in midbrain | Carries cerebellar motor commands to spinal cord

What do rubrospinal lesions cause?

Slowness in movement (temporary)

Where does the red nucleus receive most of its input from?

Cerebellum

What does activation of the rubrospinal tract in animals cause?

Excitation of flexor muscles | Inhibitor of extensor muscles

What does the tectospinal tract coordinate?

Voluntary head and eye movements - postural movements of the head in response to visual and auditory stimuli

Where does the tectospinal tract originate? Where does it receive afferents from? What does it project to?

Superior colliculus/optic tectum Retina Contralateral cervical spinal cord (terminates in rexed laminae VI, VII, and VIII)

What is the medial vestibulospinal tract a continuation of?

Medial longitudinal fasciculus

What does the medial vestibulospinal tract mediate?

Involuntary (reflex) co-ordination of the head and neck muscles with the extraocular eye muscles

The major descending motor tracts act on ______ to modulate the strength and activity of ____ pathways.

Interneurones | Reflex

What does spasticity mean? What is it characteristic of?

Abnormally increased muscle tone Increased tendon reflexes Characteristic of upper motor neuron lesions

What does clonus mean?

Series of jerky contractions of a particular muscle

What is hyper-reflexia?

Abnormally brisk tendon reflex seen in one or more muscles

What is decorticate posturing (talk about arms, wrists, fingers, legs and feet)?

Arms are adducted and flexed Wrists and fingers flexed on the chest Legs may be internally rotated and stiffly extended Plantar flexion of the feet

What does decorticate posture indicate?

Damage to corticospinal tract in midbrain

What is decerebrate posturing (talk about arms, wrists, fingers, legs and feet)?

Arms are adducted and extended Wrists pronated and the fingers flexed Legs may be internally rotated and stiffly extended Plantar flexion of the feet

What does decerebrate posturing indicate?

Severe injury to the brain at the level of the brainstem, including damage to corticospinal and rubrospinal tracts.

What is decerebrate posture thought to be due to? Which particular tract? Which nucleus is damaged?

``` Excessive activity (disinhibition) in the extrapyramidal system Vestibulospinal tract (normally under tonic inhibition by corticobulbospinal tract and red nucleus) Red nucleus ```

Which tract is predominantly affected in decorticate posture?

Corticospinal

Which is more favourable - decerebrate or decorticate posture?

Decorticate

____ posture may progress to _____ posture?

Decorticate to decerebrate

Acute effects of lesions of motor cortex - what is initially seen? (1) What is seen during recovery? (3)

Initial paralysis | During recovery there is weakness, clumsiness & fatigue of movements.

Why does recovery occur (in terms of motor cortex lesions)?

Plasticity

Larger lesions lead to ______ recovery and _______ loss of certain movement.

Slower | Permanent

Chronic effects of lesions of motor cortex - what reflex is particularly characteristic?

Clasp-knife reflex

What is hemiplegic dystonia?

Spasticity combined with profound motor weakness - persistent flexion of arms and extension of legs

What is spinal shock?

A clinical condition that occurs after acute damage to the spinal cord (includes damage to any of the descending tracts).

What are the acute effects of spinal shock? (3)

Paralysis or paresis Reduced reflex responses in all muscles below the region of injury In its severest form, all reflexes at all levels of the cord below the lesion are inactive.

What are the chronic effects of spinal shock?

``` Weak monosynaptic reflexes reappear Crossed extensor reflexes may also recover Hyperreflexia Clonus Babinski sign ```

What does damage to the corticospinal tract cause? (2)

Paralysis and weakness of voluntary movement | Hyperactive tendon reflexes

Loss of bladder/bowel control, loss of temperature regulation, loss of blood pressure regulation... these are signs of damage to what tract?

Reticulospinal tract

Vestibulospinal tract damage causes...

Loss of ability to stand upright/balance properly

Damage to both reticulospinal and vestibulospinal tracts causes...? (2)

Poor gait | Loss of ability to walk, sit and move freely

What is the difference in distribution between UMN lesions and LMN lesions?

Upper motor neuron lesion - always groups of muscles, it is never individual. Lower motor neuron - segmental, limited to muscles innervated by damaged motor neurons or their axons

What is the difference in muscle tone between UMN lesions and LMN lesions?

UMN - increased tone | LMN - decreased tone

What is the difference in reflexes between UMN lesions and LMN lesions?

UMN - hyperactive reflexes | LMN - absent or decreased reflexes

What is the difference in paralysis between UMN lesions and LMN lesions?

UMN - spastic | LMN - flaccid

Motor Systems Flashcards

(80 cards)