Motor Control #2 Flashcards
what inputs into the MN
1) descending tracts
2) spinal interneurons (eg 1a inhibitory neurons)
3) Propriospinal neurons
THe three main receptors that control movement are
Muscle spindles ( change in length and speed of this change) Golgi tendon organs Nociceptive (pain) receptors on skin (also joint receptors)
Why does the motor system control movement WITH sensory systems
We need to recieve signals coming BACK from muscles/ tendons /joints to give us info to the CNS on how the movement went.
Where else do we get info in for movements
Vestibular retina auditory offactory skin receptors
What are the three main reflexes?
Stretch
Reverse myotatic
flexion (withdrawal) reflex and cross extension
Why do we care about reflexes?
They indicate neurological disorders.
Five elements of spinal reflexes
receptors afferent fibres central synaptic relays efferent motor fibres effectors
What is the stretch reflex? How do we test?
evoked from stretch or vibration of muscle
and monosynaptic reflex (only one in body)
Hit quads tendon. this streches the muscle spindles and activates them in synchrony. AP induced in 1a afferents, evoke post-synaptic potential in alpha-MN, induce AP and muscle contraction occurs.
Components of stretch reflex
receptors= muscle spindles afferent fibres= 1a afferents central synaptic relays =synapses on a-MN efferent motor fibres= alpha MN axons effectors- extrafusal fibres
Whats reciprocal inhibition
Additonal synapses on 1a inhibitory interneurons, from 1a collateral afferents. these inhibit antagonist muscles. eg) when bicep contracts, triceps relaxes
What is Gamma-MN’s role
to innervate the muscle spindle fibres (at the periphery) causing them to stretch. this means that during muscle contraction the spindles aren’t ‘unloaded’ and info about the change of length is still being sent. when alpha-MN are activated there is an almost synchronised activation of gamma-MN
what are golgi tendon organs
receptors involved in the reverse myotactic reflex. can cause the muscle to lose tension during a muscular task, to protect the muscle from overloading. The 1b afferents synapse on 1b inhibitory interneurons, that hyperpolarize and inhibit the cell bodies of alpha-MN, so the muscle RELAXES. At the same time, the antagonistic muscles are activated
Where would you find golgi tendon organs?
In tendons of every muscle
Components of reverse myotactic reflex?
receptors= golgi tendon organs afferent fibres= 1b afferents central synaptic relays= 1b afferents to 1b inhibitory interneurons which inhibit alpha-MN efferent motor fibres= axons of alpha-MN effectors= muscles
Components of flexion withdrawal reflex
receptors= nociceptors afferent fibres= type III and IV fibres central synaptic relays= to excitatory interneurons which excite a MNs controling flexors efferent motor fibres= axons of alpha-MN effectors= flexor muscles
