Introduction to Motor Systems Flashcards
- General overview of unit content + assessments - Types of motor behaviour, feedback/feedforward control and motor hierarchy
3 types of motor behaviour
- reflexes
- rhythmic movements
- voluntary movements
reflexes
- involunatry
- unconscious
- patterns of muscle contractions and relaxations usually ellicited by a peripheral stimulus
what do reflexes involve
- spatial and temporal patterns of contractions
- depend on type of sensory receptors stimulated and strength of stimulation
muscle reflexes and receptors
- receptors in muscles produce stretch reflexes
- cutaneous receptors produce withdrawl reflexes
what are spinal reflexes used to check
functioning of afferent and efferent pathways
rhythmic movements
rhythmic motor patterns include breathing, chewing, and activities such as swimming and running
- often involve alternating contractions an relaxation of muscles on either side of the body
what are rhythmic motor patterns controlled by
circuits that mainly reside in the spinal cord
- often spontaneous e.g. voluntary BUT
- circuits are entrained by a peripheral stimulus
what is entrainment
the process of synchronising one system’s motion or signal frequency to another system
voluntary movements
- self-initiated and under conscious control
- can be used to complete a task
- but can also be triggered by an external event e.g. braking at a red light
- get more accurate the more we practice
how does the nervous system learn to deal with the physical world?
- feedforward control
- feeback control
feedforward control
NS anticipates future events based on prior experience. Initiates pre-emptive strategies based on this
feedback control
NS using sensory signals from the body to monitor the position of the limbs. Uses feedback signals to modify the position and tension in limbs as needed
feedback control
reference signal representing the bodies desired state is compared to feedback signals from sensors in the muscles and joints. Any difference we need an error signal to adjust muscles to minimise error
control of error in feedback other name
gain
gain
- determines the efficay of feedback systems
- a dynamic system to control for execution error when processing sensory input
how can gain systems be altered
providing more or less ‘signal’ to correct for error/ fine tuning
- whether a signal is attenuated or amplified depends on whether that information contributes to or distracts from attaining goal
gains reduced
for stability and to filter disruptive or self-generated feedback
gains enhanced
facilitate online motor control and movement adaptation
High gain
- rapid to correct for errors
- vulnerable to environmental chages and long-delays between sensing and action
- prone to over-correction
- can lead to oscillations
what are oscillations in terms of gain
further correction of the over-correction
low gain
- slower to correct errors
- less oscillatory behaviour
- most physiological feedbacl control is lowgain eg. postural
what does sensory gain allow
allows animals to fine tune the impact that feedback information has on moto behavioural output
feedforward control
acts in advance of certain perturbations
(before stimulus e.g. before ball hits hand)
- experience is important
example of feedforward
when attempting to catch the ball we use visual information to help catch the ball.
- previous experience of catching the ball enables us to better predict the time of the balls impact and contract the opposing arm muscle before the ball hit
- (before feedback)
What receptors send feedback
cutaneous receptors in the hand and ar muscles after the ball lands in your hand
rapid stretch reflex
controlled by spinal circuits
what happens when you plan to catch a ball
feedforward machanisms causes agonist and antagonist muscles surrounding elbow joint to contract
what 3 key principles does catching a ball illustrate for feedforward control
- it is critical for fast movements
- relies on NS ability to predict the future based on past experiences of sensory events
- starts from cortex and interact with spinal cord
where does feedback control start from
the muscles and interacts with spinal cord
how is motor control organised
hierarchically
what are the 2 key features of motor control
- hierarchical and distributed between spinal cord, brain stem and forebrain
- sensory information processed dynamically and in parallel systems to motor information allowing it to influence the evolution of movement
motor control hierarchy
- spinal cord at the bottom (relfexes and rhythmic movements)
- brain stem (2 pathways descend and project to spinal cord)
- cortex (highest level)
- cerebellum and basal ganglia
2 descending brain stem pathways
- medial descending systems
- lateral descending systems
what is the medial descending system for
with core muscles and posture control
what is lateral descending pathway for
distal muscles and voluntary goal directed movements
role of the cortex is muscle hierarchy
- primary motor cortex and multiple premotor areas regulate activity in brain stem descending tracts and project to spinal cord
role of cerebrellum and basal ganglia in motor control
regulating, planning and coordinating muscles during voluntary movements
what do spinal motor neurons do
execute movements
what do lateral and medial descending pathways from the brain stem do
influence activity of circuits in the spinal cord
what does cerebral cortex do
controls action of motor neurons in the brain stem and spinal cord
cortical areas involved in motor control
prefrontal, parietal, temporal
subcortical areas in motor control and how do they do this
basal ganglia and cerebellum regulate activation of motor cortex via activation of thalamus
