1b Motor Cortical Control Flashcards
What is meant by the hierarchical organisation?
high order areas of hierarchy are involved in more complex tasks, and lower level areas of hierarchy perform lower level tasks
What do the cerebellum and the basal ganglia do in the motor system of heirarchy?
adjust the commands received from the other parts of the motor system
What are the two pyramidal descending tracts?
corticospinal
corticobulbar
Why are the pyramidal tracts called pyramidal?
because they pass through the pyramids of the medulla
What do the pyramidal descending tracts do?
voluntary movement of the body and face muscles
What are the extrapyramidal tracts?
descending tracts which do not pass through the pyramids of the medulla
Which descending tracts are responsible for the involuntary movements of balance, posture and locomotion?
Extrapyramidal
Where is the primary motor cortex located?
Anterior to the central sulcus
What does the primary motor cortex do?
Controls fine, discrete and precise voluntary movements
What does the premotor area do?
Involved in planning movements, by regulating externally cued movements
what does the supplementary motor area do?
Planning complex movements and becomes active prior to voluntary movements
Where does the lateral corticospinal tract decussate?
In the medulla - innervates the limb muscles
Where does the anterior corticospinal tract decussate?
Spinal cord - innervates the trunk muscles
What is the principal motor tract for voluntary movement of the face and the neck?
Corticobulbar
What is the function of the vestibulospinal tract?
Stabilise head during body movements, or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments
What is the function of the reticulospinal tract?
Most primitive descending tract - from medulla and pons
Changes in muscles tone associated with voluntary movement
Postural stability
What is the function of the tectospinal?
Orientation of the head and neck during eye movements
What is the function of the rubrospinal tract?
Innervate lower motor neurons of flexors of the upper limb
What is paresis?
graded weakness of movement
What are the three negative signs of an upper motor neuron lesion?
Loss of voluntary movement
Paresis
Paralysis = complete loss of voluntary muscle activity
What is spasticity?
Increased muscle tone
What is hyper-reflexia?
Exaggerated reflexes
what is clonus?
Abnormal oscillatory muscle contraction
What are the positive signs of an upper motor neurone lesion
?
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
what is Apraxia?
disorder of skilled movement - patients lose information about how to perform skilled movements
Lesions to which areas can cause apraxia?
Frontal lobe and the inferior parietal lobe - premotor cortex, and supplementary motor area
What two diseases are the most common causes of apraxia?
Stroke and dementia
What is seen in patients with a lower motor neuron lesion?
Weakness
Hypotonia
Fibrillations
Fasciculations
Hyporeflexia
Muscle atrophy
What is Fasciculations?
damaged motor units produce spontaneous action potentials, resulting in a visible twitch
What is the difference between fasciculations and fibrillations?
Fasciculations = damaged motor units producing twitching,
Fibrillations = individual muscle fibres producing twitching
What is motor neurone disease also known as?
Amyotrophic Lateral Sclerosis
What are the upper motor neuron signs of motor neuron disease?
Spasticity (increased tone of limbs and tongue)
Brisk limbs and jaw reflexes
Babinski’s sign
Loss of dexterity
Dysarthria (difficulty speaking)
Dysphagia (difficulty swallowing)
What are the lower motor neuron signs of motor neuron disease?
Weakness
Muscle wasting
Tongue fasciculations and wasting
Nasal speech
Dysphagia
What are the two nucleuses which make up the basal ganglia called?
Lentiform nucelus and caudate nucleus
What makes up the lentiform nucleus?
The putamen and globus pallidus
What is the function of the basal ganglia?
Making the decision to move
Elaborating associated movements
Moderating and coordinating movements
Performing movements in order
What is parkinsons disease/
Degeneration of the dopaminergic neurons that originate in the substantia nigra and project to the striatum
What are the five associated symptoms of Parkinsons?
Bradykinesia
Hypomimic face
Akinesia
Rigidity
Tremor at rest
What is bradykinesia?
slowness of (small) movements (doing up buttons, handling a knife)
What is hypomimic face?
face - expressionless, mask-like (absence of movements that normally animate the face)
What is Akinesia?
difficulty in the initiation of movements because cannot initiate movements internally
What is rigidity?
muscle tone increase, causing resistance to externally imposed joint movements
What is a pill rolling tremor?
When the patients hands tremor as if they were polling a pill between two fingers, which with time can spread to other parts of the body
What is Huntington’s disease?
Degeneration of GABAergic neurons in the striatum, caudate and then putamen
What causes Huntingtons disease?
CAG repeat on chromosome 4
What are some symptoms of Huntington’s disease?
Choreic movements
Rapid jerky movements - hands and face affect
Speech impairement
Difficulty swallowing
Unsteady gait
Cognitive decline and dementia
What is the most common cause of Ballism?
Stroke which affects the subthalamic nucleus
What is Ballism?
Contralateral, uncontrolled flinging of the extremities
What separates the cerebellum from the cerebrum?
The tentorium cerebelli
What is the function of the vestibulocerebellum?
Regulation of gait, posture and equilibrium
Coordination of head movements with eye movements
What does damage to the vestibulocerebellum cause?
gait ataxia and tendency to fall (even when patient sitting and eyes open)
What is the function of the spinocerebellum?
Coordination of speech
Adjustment of muscle tone
Coordination of limb movements
What can cause degeneration and atrophy of the spinocerebellum?
chronic alcoholism
What does damage to the spinocerebellum cause?
Abnormal gait and stance (wide based)
What is the function of the cerebrocerebellum?
Coordination of skilled movements, cognitive function, attention and processing of language
What does damage to the cerebrocerebellum result in?
Affects arms (coordinated movments) and speech
What is Ataxia?
General impairments in movement coordination and accuracy. Disturbances of posture or gait: wide-based, staggering (“drunken”) gait
What is dysmetria?
Inappropriate force and distance for target-directed movements (knocking over a cup rather than grabbing it)
What is Dysdiadochokinesia?
Inability to perform rapidly alternating movements (rapidly pronating and supinating hands and forearms)
What is scanning speech?
Staccato speech, due to impaired coordination of speech muscles
What are the main signs of cerebellar dysfunction?
Ataxia
Dysmetria
Intention remor
Scanning Speech
Dysdiadochokinesia
What causes a fasciculation?
When the muscle fibres of a motor unit lose their nerve supply - they become denervated
Axons of the remaining motor unit grow and reach out to the denervated muscle fibres - reinnervation takes place
Therefore the resulting motor unit is larger and prone to ectopic generation of electrical stimuli in the distal axons which cause muscle contraction = fasciculation
What is the striatum?
Caudate + putamen
What is the lentiform nucleus?
Putamen + external globus pallidus
What is the result of a stroke affecting the subthalamic nucleus?
Ballism
Where does the lateral corticospinal tract decussate?
In the medulla
What is meant by functional segregation?
Motor system organised in a number of different areas that control different aspects of movement
