neural control of movement Flashcards
name the 4 structures that control movement
lower motoneurons
upper motoneurons
cerebellum
basal ganglia
what do LMNs do?
produce muscle contractions via motor units
what is the general function of UMNs?
produce voluntary movements
give commands to the LMNs which are effectors
what is the function of the cerebellum in movement?
coordinate muscle movement - esp complicated multi-joint movements
what is the function of basal ganglia?
contain motor programs for the initiation and maintenance of movements
what are the 4 anatomical points where lower motor neuron weakness can occur?
origin of the signal in the anterior horn of the spinal cord
where axons go through the ventral horn then join a nerve lower down
neuromuscular junction
muscle
what is a clinical feature of lower motoneuron damage?
muscle wasting esp in bulbar muscles in the tongue and the upper and lower limb
which neurons never innervate muscles?
upper motoneurons
where are UMN cell bodies found?
in the cerebral cortex - mainly the precentral gyrus
what are the 3 functionally distinct motor pathways that upper motoneurons contribute to?
CST
rubrospinal tract
vestibulospinal and reticulospinal tracts
what is the function of the CST?
precise movements
what is the function of the rubrospinal tract?
large muscle movements and facilitates flexor movements
what is the function of the o vestibulospinal and reticulospinal tracts?
posture & balance, muscle tone, position of head and limbs
what does the corticobulbospinal tract supply?
the musculature of the head and neck
what does voluntary movement require?
knowledge of where the body is in space
where it intends to go
selection of a plan and how to get there
what are the functions of UMNs?
• Excitation of muscles • Inhibition of muscles • Reflex modulation (e.g. Jendrassic) • Efference copy (important for smooth movements) activation of other brainstem UMNs
what is an efference copy?
an internal copy of a movement signal
used to reduce cognitive load by decreasing sensory processing of incoming sensory info
what regions of the cortex are involved in motor control?
ore frontal cortex
frontal eye fields
pre motor cortex and supplementary cortex
primary motor cortex
how does the anatomical position of the cortical region relate to its role?
the more anatomically anterior the cortical region, the more complex/abstract the role in movement
what are the steps needed to carry out a movement and what regions assist in this?
decision to move - areas 5 and 7
plans to move are stored until required - association motor cortex - area 6
activation of descending pathways - area 4
what is the result of signal mismatch?
uncoordinated movements
what are the 3 main structures of the cerebellum?
anterior lobe
tonsils
posterior lobe
what are the 3 main cerebellum pathways?
vestibulocerebellum
spinocerebellum
cerebrocerebellum
what is the function of vestibulocerebellum pathway?
balance and posture
eye movements
what is the function of spinocerebellum pathway?
locomotion
voluntary movements of arms and legs
what is the function of cerebrocerebellum pathway?
skilled motor tasks, e.g. speech, hand-eye co-ordination and cognitive eye movements
what are the basal ganglia?
a group of neurons involved in brake theory
describe the brake theory
if you stay still you must brake all movements (except the reflexes that keep you in the position)
to move, you must break some of these postural reflexes and release the brakes on voluntary movement
what are the 5 nuclei of basal ganglia?
caudate, putamen, globus pallidus, substantia nigra, subthalamic nuclei
what do the 5 nuclei of basal ganglia do?
o Involved with initiation and maintenance of motor actions – decision making
o Work with motor association cortex to determine
Strength of the response
Organise correct sequences of activity
what causes tension in muscles?
partial state of contraction
what does muscle tone depend on?
monosynaptic reflexes
what is muscle tone maintained by?
reflexively
what regulates muscle tone?
descending motor pathways
where is most of the body weight found?
anterior to the vertebral column
which muscles are important in maintaining postural stance?
deep back muscles
how is muscle tone constantly finely adjusted?
by muscle fibres contracting in relays
what does damage to the cerebellum cause?
ataxia and hypotonia
what is ataxia?
group of disorders that affect coordination, balance and speech
what is hypotonia?
a state of low muscle tone
what does damage to the basal ganglia cause?
hyper/hypokinesia
what is hyperkinesia?
exaggerated unwanted movement
what is hypokinesia?
decreased bodily movement
what does damage to the associated motor cortex cause?
apraxia
what is apraxia
difficulty performing movements they already know
what does damage to descending pathways cause?
spasticity and hypertonia
define spasticity
an increase in muscle tone due to the loss of inhibition of gamma motoneurons
define rigidity
increase in muscle tone due to the loss of inhibition of alpha motoneurons
what controls the strength of stretch receptors?
gamma motoneurons
what causes spasticity?
Increased excitation/decreased inhibition of gamma MNs increases tension of intrafusal muscle fibres which becomes hypersensitive to muscle stretch
what are neuromuscular disorders?
conditions affecting muscles, nerves, motor or sensory cell body or the neuromuscular junction – the area where muscle and nerve make connection
what is the function of association motor cortex and BG?
strategy – planning & selecting programmes to produce desired movements
what is the function of primary motor cortex and CB?
tactics – sequences of muscle contractions over time to produce smooth accurate movements
what is the function of brainstem and spinal cord in movement?
execution of voluntary movement and any necessary postural adjustment.
