Motor Cortical Control

Question 1

What is the Hierarchical organization of Motor control?

Answer 1

Higher orders - more complex tasks, e.g. programme & decide on movements, coordinate muscle activity.

Lover level areas - lower level tasks e.g. execution of movement.

Question 2

How is the Motor system segregated?

Answer 2

Number of different areas that control different aspects of movement.

Question 3

What are the two types of Major descending tracts?

Answer 3

Pyramidal
Extrapyramidal (do not pass through the pyramids of the medulla)

Question 4

What are some examples of Pyramidal tracts and their functions?

Answer 4

Corticospinal, Corticobulbar

Motor cortex to spinal cord or cranial nerve nuclei in brainstem.

Voluntary movements of body and face.

Question 5

What are some examples of Extrapyramidal tracts and their function?

Answer 5

Vestibulospinal, Tectospinal, Reticulospinal, Rubrospinal.

Brainstem nuclei to spinal cord.

Involuntary (autonomic) movements for balance, posture & locomotion.

Question 6

Where is the Primary motor cortex located, and what is its function?

Answer 6

Precentral gyrus, anterior to the central sulcus.

Controls fine, discrete, precise voluntary movements.

Provides descending signals to execute movements

Question 7

Where is the Premotor area located, and what is its function?

Answer 7

Anterior to primary Motor cortex

Involved in planning movements and regulates externally cued movements. Seeing an apple and reaching out for it.

Question 8

Where is the Supplementary motor area located, and what is its function?

Answer 8

Anterior and medial to PMC

Involved in planning complex movements, internally cued (speech). Becomes active prior to voluntary movement.

Question 9

What makes up the Corticospinal tract?

Answer 9

Lateral Corticospinal tract - 85-90% crossed fibres , Limb muscles.

Anterior Corticospinal tract - 10-15% uncrossed fibres, trunk muscles.

Question 10

What does the corticospinal tract pass through to get to the medulla

Answer 10

Cerebral Peduncle

Question 11

What does somatotopic mean in regard to the brain?

Answer 11

A particular region in the brain correlates to contol of a particular region in the body

Question 12

What is the Corticobulbar tract responsible for?

Answer 12

Principal motor pathway for voluntary face movements of the face and neck.

Question 13

Which nuclei are responsible for the movements of the Extra ochlear muscles?

Answer 13

Oculomotor nucleus
Trochlear nucleus
Abducens nucleus

Question 14

Which nucleus is responsible for the muscles of mastication?

Answer 14

Trigeminal Motor nucleus

Question 15

Which nucleus is responsible for muscles of the face?

Answer 15

Facial nucleus

Question 16

Which nucleus is responsible for muscles of the tongue?

Answer 16

Hypoglossal nucleus

Question 17

What is the responsibility of the Vestibulospinal tract?

Answer 17

Stabilise head during body movements, or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments

Question 18

What is the responsibility of the Reticulospinal tract?

Answer 18

Most primitive descending tract - from medulla and pons
Changes in muscles tone associated with voluntary movement
Postural stability

Question 19

What is the responsibility of the Tectospinal tract?

Answer 19

From superior colliculus of midbrain

Orientation of the head and neck during eye moveme

Question 20

What is the responsibility of the Rubrospinal tract?

Answer 20

From red nucleus of midbrain
In humans mainly taken over by corticospinal tract
Innervate lower motor neurons of flexors of the upper limb

Question 21

What are the negative signs of an upper motor neuron lesion?

Answer 21

Loss of voluntary motor function
Paresis: graded weakness of movements
Paralysis (plegia): complete loss of voluntary muscle activity

Question 22

What are the positive signs of an upper motor neurone lesion?

Answer 22

Increased abnormal motor function due to loss of inhibitory descending inputs
Spasticity: increased muscle tone
Hyper-reflexia: exaggerated reflexes
Clonus: abnormal oscillatory muscle contraction
Babinski’s sign

Question 23

What is Apraxia?

Answer 23

A disorder of skilled movement. Patients are not paretic but have lost information about how to perform skilled movements

Question 24

What causes Apraxia?

Answer 24

Lesion of inferior parietal lobe, the frontal lobe (premotor cortex, supplementary motor area - SMA)
Stroke & dementia are the most common causes

Question 25

What are the signs of Lower motor neuron lesions?

Answer 25

Weakness Hypotonia (reduced muscle tone) Hyporeflexia (reduced reflexes) Muscle atrophy Fasciculations: damaged motor units produce spontaneous action potentials, resulting in a visible twitch Fibrillations: spontaneous twitching of individual muscle fibres; recorded during needle electromyography examination

Question 26

What is an example of a disease that effects both upper and motor neurons?

Answer 26

Motor neuron disease MND e.g. ALS

Question 27

What does ALS effect?

Answer 27

``` Progressive neurodegenerative disorder of the motor system. Affecting; Upper motor neurons Brainstem lower motor neurons Axon bundles tongue intercostal muscles spinal cord lower motor neurons lower limb muscles upper limb muscles ```

Question 28

What are the upper motor neuron signs of MND?

Answer 28

``` Spasticity (increased tone of limbs and tongue) Brisk limbs and jaw reflexes Babinski’s sign Loss of dexterity Dysarthria (difficulty speaking) Dysphagia (difficulty swallowing ```

Question 29

What are the lower Motor neuron signs of MND?

Answer 29

``` Weakness Muscle wasting Tongue fasciculations and wasting Nasal speech Dysphagia ```

Question 30

What makes up the structure of the basal ganglia?

Answer 30

Caudate nucleus Lentiform nucleus (putamen + external globus pallidus) – together caudate and putamen are known as the striatum Nucleus accumbens Subthalamic nuclei Substantia nigra (midbrain) Ventral pallidum, claustrum, nucleus basalis (of Meynert)

Question 31

What are the functions of the basal ganglia?

Answer 31

Decision to move Elaborating associated movements (e.g. swinging arms when walking; changing facial expression to match emotions) Moderating and coordinating movement (suppressing unwanted movements) Performing movements in order

Question 32

What is the structural order of the basal ganglia?

Answer 32

``` C - caudate nucleus P – putamen G – (external) globus pallidus T - thalamus Acc – nucleus accumbens Am – amygdala AC – anterior commisure ```

Question 33

What happens in Parkinson's disease?

Answer 33

Degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum

Question 34

What are the signs of Parkinson's disease?

Answer 34

Bradykinesia - slowness of (small) movements (doing up buttons, handling a knife) Hypomimic face - expressionless, mask-like (absence of movements that normally animate the face) Akinesia - difficulty in the initiation of movements because cannot initiate movements internally Rigidity - muscle tone increase, causing resistance to externally imposed joint movements Tremor at rest - 4-7 Hz, starts in one hand (“pill-rolling tremor”); with time spreads to other parts of the body

Question 35

What happens in Huntington's disease?

Answer 35

Degeneration of GABAergic neurons in the striatum, caudate and then putamen

Question 36

What are the signs of Huntington's disease?

Answer 36

Choreic movements (chorea - dance) rapid jerky involuntary movements of the body; hands and face affected first; then legs and rest of body Speech impairment Difficulty swallowing Unsteady gait Later stages, cognitive decline and dementia

Question 37

What are the genetics of Huntington's disease?

Answer 37

Genetic neurodegenerative disorder Chromosome 4, autosomal dominant CAG repeat

Question 38

What is Ballism?

Answer 38

Symptoms occur contra laterally, uncontrolled flinging of the extremities. Usually occurs due to a stroke affecting the subthalamic nucleus.

Question 39

Where is the Cerebellum located, and what is its function?

Answer 39

Located in posterior cranial fossa Separated from cerebrum above by tentorium cerebelli Coordinator & predictor of movement

Question 40

What is the function of the Vestibulocerebellum?

Answer 40

Regulation of gait, posture and equilibrium | Coordination of head movements with eye movements

Question 41

What are the signs of dysfunctions of the Vestibulocerebellum?

Answer 41

Damage (tumour) causes syndrome similar to vestibular disease leading to gait ataxia and tendency to fall (even when patient sitting and eyes open

Question 42

What is the function of the Spinocerebellum?

Answer 42

Coordination of speech Adjustment of muscle tone Coordination of limb movements

Question 43

What does damage to the Spinocerebellum present as?

Answer 43

Damage (degeneration and atrophy associated with chronic alcoholism) affects mainly legs, causes abnormal gait and stance (wide-based)

Question 44

What is the function of the Cerebrocerebellum?

Answer 44

Coordination of skilled movements Cognitive function, attention, processing of language Emotional control

Question 45

What does damage to the Cerebrocerebellum present as?

Answer 45

Damage affects mainly arms/skilled coordinated movements (tremor) and speech

Question 46

Define Ataxia

Answer 46

General impairments in movement coordination and accuracy. Disturbances of posture or gait: wide-based, staggering (“drunken”) gait

Question 47

Define Dysmetria

Answer 47

Inappropriate force and distance for target-directed movements (knocking over a cup rather than grabbing it)

Question 48

Define Intention tremor

Answer 48

Increasingly oscillatory trajectory of a limb in a target-directed movement (nose-finger tracking)

Question 49

Define Dysdiadochokinesia

Answer 49

Inability to perform rapidly alternating movements (rapidly pronating and supinating hands and forearms)

Question 50

Define scanning speech

Answer 50

Staccato, due to impaired coordination of speech muscles

Question 51

What is similar in all the main signs of cerebellar dysfunction?

Answer 51

Apparent only on movement