Cortical motor function Flashcards
How is the Motor system organised?
Into a number of different areas that control different aspects of movement
Explain the hierarchical organisation of motor control
High order areas of hierrachy are involved in more complex tasks
Lower level areas of hierarchy perform lower level tasks (excecution of movement)
What is the function of the primary motor cortex?
Control fine, discrete, precise voluntary movement
Provides descending signals to execute movement
What does the motor cortex consist of?
Primary motor cortex
Premotor cortex
Supplementary motor area
What does the association cortex consist of?
Parietal and frontal cortex
What does the brainstem do?
Centre of integration of different inputs coming from the vestibular, vision and auditory systems
What does the motor cortex do?
It is where movements are programmed and where the voluntary movements are initiated
What does the association cortex do?
It influences the planning and execution of movements
Where is the location of the primary motor cortex?
Precentral gyrus, anterior to the central sulcus
Where is the location of the premotor cortex?
Frontal lobe, anterior to M1
What is the function of the premotor cortex?
Planning of movements
Regulates externally cued movements
Where is the location of the supplementary motor area?
Frontal lobe anterior to M1, medially
What is the function of the supplementary motor area?
Planning complex movements; programming sequencing of movements
Regulates internally driven movements
SMA becomes active when thinking about a movement before executing that movement
What is the function of the posterior parietal cortex?
Ensures movements are targeted accurately to objects in external space
What is the function of the prefrontal cortex?
Involved in selection of appropriate movements for a particular course of action
What is paresis?
graded weakness of movements
What is paralysis?
complete loss of muscle activity
What is spasticity?
Increased muscle tone
What is hyperreflexia?
exaggerated reflexes
What is a clonus?
abnormal oscillatory muscle contraction
What is apraxia?
A disorder of skilled movement. Patients are not peretic but have lost information about how to perform skilled movements
Apraxia is caused by a lesion of…
…inferior parietal lobe, frontal lobe (premotor cortex, supplementary motor area)
What are the most common causes of apraxia?
Stroke, dementia
Lower motor neurone lesions affect which motor neurone?
The 2nd motor neurone (the one that starts in the grey matter of the spinal cord and exits to form peripheral nerves
List the signs of lower motor neurone lesions
Weakness Hypotonia Hyporeflexia Muscle atrophy Fasciculations Fibrillations
What is hypotonia?
Reduced muscle tone
What is hyporeflexia?
Reduced reflexes
What is meant by fasciculations?
Damaged motor units produce spontaneous action potentials, resulting in a visible twitch
What is meant by fibrillations?
Twitch of individual muscle fibres - these aren’t visible to the naked eye but can be recorded if the patients have needle electromyography
Motor neurone disease can affect which neurones?
Only upper motor neurones
Only lower motor neurones
Both
When MND affects both upper and lower motor neurones, it is called…
…Amyotrophic lateral sclerosis
Listthe signs of ALS
Increased muscle tone Brisk limbs and jaw reflexes Babinski's sign Loss of dexterity Dysarthria - difficulty with their speech Dysphagia
List the upper motor neurone signs of MND
Increased muscle tone Brisk limbs and jaw reflexes Babinski's sign Loss of dexterity Dysarthria - difficulty with their speech Dysphagia
List the lower motor neurone signs of MND
Weakness Muscle wasting Tongue fasciculations and wasting Nasal speech Dysphagia
What does the basal ganglia consist of?
Caudate nucleus
Lentiform nucleus (putamen & external globus pallidus)
Subthalamic nucleus
Substantia nigra
Ventral pallidum, claustrum, nucleus accumbens, nucleus basalis of Meynert
