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Lecture 4

KIN 155 Lecture Notes - Lecture 4: Stimulus Modality, Mental Chronometry, Stretch Reflex


Department
Kinesiology
Course Code
KIN 155
Professor
Bill Mc Ilroy
Lecture
4

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Kin 255 09/20/2012
Lecture 4
CNS: Central Nervous System
PNS: Peripheral Nervous System
Grey matter - in the middle of spinal cord – non-myelinated. Where
dendrites, terminal boutons etc are placed.
White matter – surrounding the grey matter – myelinated, travel
paths, where the axon is.
Parts of the CNS
Spinal cord
Brain stem (medulla, pons, midbrain)
Cerebellum
Basal Ganglia
Cortex
Ganglia (nuclei) - group of cell body that come together- regions of
grey matter
Reflexes
Monosynaptic stretch reflex (one synapse)
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- receptor for this is in the muscle spindle. Eg. Tendon tap with a
hammer- it stretches the muscle so you get a kick.
-15-20ms for this reflex
What happens if the muscle shortens?
You will have and alpha gamma co-activation, it keeps the spindle
ready if there is ever a need for a reaction.
Where does a single 1a fibre go?
Divergence: a neuron has many different projections to many
neurons and synapses
Convergence: a neuron receives many synapses from many
different neurons
Single 1a
100% to the homonymous
-60% to the synergists - heteronymous
-60% to the antagonist muscles
Reciprocal Activation
Agonist (prime mover muscle), antagonist and synergists
Reciprocal activation -turning on the agonist and inhibiting the
antagonist (throwing a ball)
Co-contraction- turning on both agonist and antagonist (stability)
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Myosynaptic Stretch Reflex – again
Phase dependent modulation- modulation of a reflex at different points
in a movement
Stimulate and measure the size of the reflex
We can control what happens at the synapse either pre-synaptic or
post-synaptic
Reflex Reversal
Stimulus causes a different (opposite) response under different
movement conditions
Withdrawal Reflex
Polysynaptic spinal reflex
complex reaction (multiple muscles, different body segments) –
many synapses/ interneurons
Vestibulo-ocular reflex
Vestibular input and eye muscle output
Head moves one way – eyes move the other to keep gaze on target
Reaction Time - what time really mean!
Time between the start of a stimulus and the start of the response
Process time
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