Reflexes Flashcards
Lecture 21/22/23
What will interference result in?
-increase RT
-increase performance errors
(ie. read red, see blue)
Some systems of sensory feedback
-vestibular (ear)
-cutaneous receptors
-Golgi tendon organs
-muscle spindles
Deafferentation
-caused by demyelination of large peripheral nerves
-struggle w/ touch and proprioception
AIDP
acute inflammatory demyelinating polyneuropathy
Without visual info what would you expect to see from a patient w/ deafferentation
-inaccurate, jerky movements
-large errors
How does a muscle stretch impact AP’s in muscle spindles
-increase firing rates
How does a muscle contraction impact AP’s in muscle spindles
-reduce firing rates
How do spindle receptors sense muscle length?
-muscle stretch deforms and opens ion channels
-excites spindle afferent
What produces large muscle responses?
-longer and larger stimuli
Rapid force applied to the patellar tendon causes…
the quadriceps muscle to contract
What increases latency in neural reponses?
-increased synapses
Homonymous muscle
same muscle stretched by stimulus
purpose of gamma motor neurons
-maintain spindle sensitivity
-maintains length of intrafusal fibres (muscle spindle) during voluntary muscle contraction
Alternate names for long latency reflexes (LLR) inculde?
-long loop
-transcortical
-polysnaptic
Describe attributes of short-latency reflexes (SLR’s)
-spinal proprioceptive feedback
-20 to 50ms
-simple processing capabilities
Describe attributes of long-latency reflexes (LLR’s)
-spinal feedback, plus cortical (brain) feedback)
-50 to 105ms
Describe attributes of voluntary epoch
-spinal, cortical and visual feedback
-longest to process (120+ms)
Properties of SLR
-scale w/ background muscle activity (closer/further threshold)
-scale w/ rate and amount of muscle stretch (more AP’s, more neurotransmitters, more force)
Properties of LLR
-recruit cerebral cortex
-flexible, goal-directed processing
-increase when goal is to resist mechanical perturbation (as opposed to “let go”)
Desired state
-goal of task
Motor plan
-aim to maintain/attain goal
Motor command
-activity in motor circuits (cortical or subcortical)
comparator =
brain
Expected state
-intended/planned movement
error =
difference btwn actual and expected state
purpose of error signal
adjust ongoing movement
closed-loop (feedback control system)
-uses sensory feedback to detect errors correct voluntary motor actions
executive (feedback controller)
-processes sensory info
-selects, programs appropriate response
effector
-component of peripheral motor system
-generates desired motor response
dorsal vision stream is important for…
controlling actions
ventral vision stream is important for…
perceptual judgements
exteroception
-sensory info that tells us about the state of our body in relation to the world around us
photoreceptors
-absorb photons
-trigger change in membrane potential
rods
-concentrated in peripheral
-low visual acuity
-sensitive to motion
cones
-concentrated in fovea (centre)
-high acuity
-high spatial resolution
-color vision
dorsal stream
-“where” pathway
-action guidance
ventral stream
-“what” pathway
-vision for perception (orientation), identification, recognition
form agnosia
-ventral stream damage
-selective impairments in perception
-intact control of actions
(can copy/draw, but don’t know what it is)
optic ataxia
-dorsal stream damage
-inability to use vision to guide reaching movements
info given by optic flow (vision)
-time to contact
-direction of movement
-movement
-stability and balance
-velocity of movement
low rate of expansion (EX)
freighter in the distance
high rate of expansion (EX)
deer in the headlights
Rate of expansion increases as…
time to contact decreases (closer)
Vision helps most with what type of movements
-slow, deliberate
the dorsal visual stream gives control of what type of visual feedback
fast, stimulus dependent
the ventral visual stream gives control of what type of visual feedback
-slower, task-dependent
