Sensory contributions: Proprioception and Vision

Kin 211 Human Motor Behaviour

what happens to a muscle when a load is unexpectedly applied but there is a goal to maintain body position?

there is an initial subconscious proprioceptive response as early as 30ms after the load is applied, then around 120-150ms, conscious voluntary response happens

M1: short latency/long loop reflex

Monosynaotic stretch reflex

leads to a flex of the muscle being stretched

M2: Long latency/loop reflex is sensitive to

goals and context

what is M3

voluntary response to a stimulus

Muscle spindles

react to changes in length and the rate of change in muscle fibres

sensory/afferent neuron sends information to SC

can excite motor/efferent neurone to muscle fibres

M1 response in muscle spindles

receptor = muscle spindles

sensory/afferent neuron sends signal to Motor Neuron (MN) in SC

MN sends efferent response to muscle

does not involve instruction

takes 30-50ms

M2 response

receptor = muscle spindles

innervates an interneuron and receives signals about the state of the situation (context) from higher structures (cortex or cerebellum)

is modified by instruction

takes 50-70ms

what would happen to M2 if an unexpected load is applied to a muscle but there is no goal of maintaining body position?

it would disappear because there’s nothing for it to do (no need to restore position)

Golgi tendon organs (GTOs)

location and what they detect

located in junctions bw muscles and tendons

detect changes in muscle’s tension or force

in order to prevent injusry

vestibular apparatus, where, what it gives, the two parts, and what they are sensitive to

located in inner ear

gives info about movements of head and balance

semicircular canals: sensitive to angular acceleration

otolith organs: sensitive linear acceleration

cutaneous receptors

info about touch pressure temperature and pain

joint receptors

within joint capsules

respond to limits in joint range (max flex and max extend) and pressure

proprioceptors are used for open or closed loop control?

closed: movement and balance

dorsal vision

subconscious and fast

allows for small adjustments of movements

occurs at motor program stage

travels to parietal cortex

ventral vision

conscious closed loop control

travel to inferotemporal cortex

slower

optic ataxia

problem with dorsal steam

difficulty coordinating actions

you know the what but not the where of what you’re seeing

Visual-Form Agnosia

problem with ventral steam

identify where the thing is but not what it is (forgetting what it is)

can’t identify common object until they touch it

tau

rate of expansion of object on retina, provided by dorsal vision

visual stream for object interactions and guiding actions

vision for action

visual stream for object/stimulus identification and planning

vision for perception

motor program def

a restructured set of neural commands, prepared in advance, and capable of producing movement wo the influence of feedback

stored in memory

not easily stopped

open loop control until enough time has passed and it switches to closed loop

point of no return

when there’s a 50/50 chance of being able to stop/inhibit response