**_🧠Neurology🧠 - Motor and Neuromuscular Control Flashcards
What 2 main principles is the motor control system built upon?
Hierarchical organisation
Functional segregation
What is meant by hierarchical organisation?
Higher orders of hierarchy in nervous system are involved in more complex tasks (programme and decide on movements, co-ordinate muscle activity)
Lower level areas of hierarchy perform lower level/more basic tasks (e.g. execution of movement)
What is meant by functional segregation?
Motor system organised in a number of different areas that control different aspects of movement
Outline the motor system hierarchy
What 2 categories can the major descending tracts be divided into?
Pyramidal tracts - pass through the pyramids of the medulla
Extrapyramidal tracts - do not pass through the pyramids of the medulla
What is the overall function of the pyramidal tracts?
Voluntary movements of body and face
What is the overall function of the extrapyramidal tracts?
Involuntary (automatic) movements for balance, posture and locomotion
Where to the pyramidal tracts originate and terminate?
The motor cortex to the spinal cord/cranial nerve nuclei in brainstem
Where do the extrapyramidal tracts originate and terminate?
Brainstem nuclei to the spinal cord
Name the pyramidal tracts
Corticospinal
Corticobulbar
Name the extrapyramidal tracts
Vestibulospinal
Tectospinal
Reticulospinal
Rubrospinal
Where is the primary motor cortex located?
Pre-central gyrus, anterior to the central sulcus
What is the function of the primary motor cortex?
Controls fine, discrete, precise voluntary movements
Provides descending signals to execute movements
Where is the premotor area located?
Located anterior to primary motor cortex
What is the function of the premotor area?
Involved in planning movements
Regulates externally cued movements
What is meant by an externally cued movement?
Interacting with the environment
e.g. seeing an apple and picking it up
Where is the supplementary motor area?
Located anterior and medial to the primary motor cortex
What is the function of the supplementary motor area?
Involved in planning complex movements (e.g. internally cued movements, such as speech)
Becomes active prior to voluntary movement
Describe the first part of the path of the corticospinal tract?
Upper motor neurones originating in the cerebral cortex, travel downwards, to the cerebral peduncle and into the midbrain
Where does the corticospinal tract go after the midbrain?
Into the medulla, and through the pyramids
Decussates somewhere along the pyramids
Which fibres of the corticospinal tract decussate?
85-90% of the fibres decussate (cross) - Limb muscles - lateral corticospinal tract
10-15% of the fibres do not - trunk muscles - anterior corticospinal tract
Outline the pathway of the corticospinal tract
What is the corticobulbar tract?
Principal motor pathway for the voluntary movements of the face and neck - passes through the basal ganglia
Some fibres terminate on the cranial nerve nuclei in the brainstem
What are the cranial nerve nuclei found in the brainstem, on which some fibres of the corticospinal tract terminate?
Oculomotor+trochlear nucleus
Trigeminal motor nucleus
Abducens nucleus
Facial nucleus
Hypoglossal nucleus
What is the function of the oculomtotor+trochlear nuclei?
Control eye movements
What is the function of the trigeminal motor nucleus?
Controls the muscles of the jaw
What is the function of the abducens nucleus?
Controls movements of the eye
What is the function of the facial nucleus?
Controls muscles of the face
What is the function of the hypoglossal nucleus?
Controls movements of the tongue
Outline the vestibulospinal tract
Stabilise head during body movements, or as head moves
Coordinate head movements with eye movements
Mediate postural adjustments
Outline the reticulospinal tract
Most primitive descending tract - from medulla and pons
Changes in muscles tone associated with voluntary movement
Postural stability
Outline the tectospinal tract
From superior colliculus of midbrain
Orientation of the head and neck during eye movements
Outline the rubrospinal tract
From red nucleus of midbrain
In humans mainly taken over by corticospinal tract
Innervate lower motor neurons of flexors of the upper limb
What are the two categories of signs that can be identified with an upper motor neuron lesion?
Positive and negative signs?
What are the negative signs that can be identified with an upper motor neuron lesion?
Loss of voluntary motor function
Paresis: graded weakness of movements
Paralysis (plegia): complete loss of voluntary muscle activity
What are the positive signs that can be identified with an upper motor neuron 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 Babinski’s sign?
the big toe moves upward and the other toes fan out or curl down in response to the sole of the foot being stroked with a blunt object
What is apraxia?
Disorder of skilled movement
Patients are not paretic but have lost information about how to perform skilled movements
Outline the components of the basal ganglia
Outline the basal ganglia circuitry
Don’t need to memorise, just for illustration
How are the three different types of motor unit classified?
The 3 different motor unit types are classified by the amount of tension generated, speed of contraction and fatiguability.
How does the amount of sustained force produced by the different types of motor unit compare to each other?
How do neurons affect the muscle fibres which they innervate?
Motor unit and fibre characteristics are dependent on the nerve which innervates them.
If a fast twitch muscle and a slow muscle are cross innervated, the soleus(slow twitch) becomes fast and the FDL(fast twitch) becomes slow
Outline the monosynaptic (stretch) reflex
Stretch of tendon caused by hammer sends signal up sensory neuron
Goes through a motor neuron, to the antagonist motor neuron
