motor systems Flashcards
motor behaviour
refers to the movements of the body produced as a consequence of contractions of skeletal muscles
first view of spinal reflexes
were highly specific, repeatable, unchangeable, unlearned movement patterns present in the spinal cord
this gave rise o the view of a reflex as a basic unit of behaviour, and that all behaviours were simply a long string of reflexes, with each reflex providing the stimulus to start the next
motor plan
hiearchial system
calling on lower units as needed
a plan for a series of muscle contractions
complex set of commands before an act occurs - feedback informs and fine tunes
EMG
records moment to moment positions of the body
labeled lines
each nerve input to the brain reports only a specific type of information
recognizes each modality as separate and distinct
ie/ one line signals smell, another touch and another taste
convey spatial info ie/ knowing where a mosquito is biting
what are the 6 categories in the motor behaviour hierarchy
simple reflexes, postural adjustments, locomotion, sensory orientation, species typical behaviours and acquired behaviours
simple reflexes
usually spinal but not always
ie/ knee jerk, pupillary constriction
usually involve only a few synapses
at any given level of the cord these reflect local processing and integration of corresponding sensory info from that level
usually involve only one or a couple of synapses between input side (sensory) and output side (motor)
postural adjustments
standing, head tilt, balancing
locomotion
walking, running, flying
within own species unique motor system
sensory orientation
aiming sensors at stimulus sources (turning eyes toward light)
moving body to align with environement
species typical behaviours
complex movements, but usually executed according to a pre wired plan
acquired behaviours
motor skills acquired and/or tuned through interaction with the environment
ie/ speech, tool use, fishing by bears, riding a bike
susceptible to change through experience
speed-accuracy tradeoff
for any muscle, increased speed can only come at a cost of decreased accuracy
sensory adaptation
progressed decrease in receptor’s response to sustained stimulation
allows us to ignore unimportant events
phasic receptors
a receptor in which frequency of action potentials drop rapidly as stimulation is maintained
tonic receptors
a receptor in which frequency of AP declines slowly or not at all as stimulation is maintained
closed-loop movement
accuracy is provided by the neural mechanism of using feedback from the sensory system
as a movement is executed, visual, proprioceptive or other sensory info is used to determine the accuracy of a movements
deviations from the intended movement, once detected, can be corrected “on the fly”
you can correct a movement if you felt that it was off
open-loop movemetns
some movements require maximal speed, such as a predatory attack, or an escape or grabbing for the keys that you just dropped
in these movements, the entire sequence is pre-programmed and then executed all at once (ballistic movement)
disconnection between systems and feedback, aiming for optimal speed - no time for feedback
ballistic movemetn
not subject to feedback and thus no on the fly correction
sequence of a movement is preprogrammed, and executed all at once
combinations of movements
many human movements, especially of the upper limbs combine both open loop and closed loop
ie/ visually guided reaching, the first phase is ballistic, and then the arm shoots out in the desired direction. as the hand nears the target, a closed-loop component guides the hand to the target and prepares the hand to grasp it
implicit memory
memory you can not describe - you have learned how to do it
motor ability is learned and retained through a non-conscious mechanism (bottom - up processing), as a consequence of simply doing it over again
ie/ riding a bike
cognitive stage
effortul - direct control over it
conscious guidance of the behaviour
ie/ hunting and pecking for each piano or computer key (when first learning)
what are the three stages in learning a new motor skill
cognitive stage
association stage
automatic stage
association stage
links are formed between certain actions and sucessful outcomes (and between other actions and unsuccessful outcomes)
this in the tuning phase
with enough practice, a certain pattern of movement is associated with being successful
automatic stage
once the skull has been acquired it can be rattled off as a single unit, produces smooth seamless behaviour
ie/ accomplished pianist, balance corrections in riding a bike
transcranial magnetic stimulation mapping
directly activate neurons on cortical surface which can cause a movement
has revealed that while motor skills are being learned, the cortical representation for the muscles being used actually enlarges and then shrinks down again after the skill is acquired
it is thought that this corresponds to an automatic stage, and that the learned skill is stored elsewhere in supplementary motor cortex
lowest to highest level of the motor control system
muscle
spinal cord
brainstem
motor cortex
subcortical regions - basal ganglia and thalamus
cerebellum
dorsal column system
delievers most touch stimuli to brain via dorsal columns of spinal white matter - then to thalamus
spinal cord
contains the motor neurons innervating the muscle
ventral horn motor neurons
contains skeletal muscles in response to motor commands from the brain
brainstem
nuclei project (transmit) to the spinal cord
integrates motor commands from higher levels
motor cortex
primary and supplementary areas - executive control
precentral gyrus
1/3 of axons in this tract originate from cells within here
organized via somatosensory map
major source of pyramidal tract
synergist
muscle that acts together with another muscle
antagonist
muscle that counteracts the effect of another muscle
primary motor cortex
also the precentral gyrus
executive region for initiation of movement
axons form pyrimydal tract
nonprimary motor cortex
contributes to the programming of movement
primary motor cortex to spinal cortex
main pathway for orientation of movement
skeleton
bodily movements constrained by joints
muscles use bones as levers around joints
degrees of freedom
number of directions possible in an articulation
tendons
connect muscle to bone
ligaments
connect bone to bone
flexor
muscle that flexes (bends joint)
usually toward body
extensor
muscle that straightens joint
usually away from body
myofibrils
each muscle fibers consists of
made up of myofilaments
