UMNs and spinal reflexes Flashcards
What is the function of interneurons?
integrates incoming information to generate an output to modulate responses
What processes do inhibitory interneurons mediate?
the inverse myotatic response and reciprocal inhibition
What is reciprocal inhibition?
The antagonist muscle to a contracting muscle must simulatneoulsy relax
What is the pathway for reciprocal inhibition?
The 1a afferent from the muscle spindle extensor makes an excitatory contact with an alpha motor neuron and via an inhibitory interneuron the alpha motor neuron supplying the flexor is inhibtied
What is the flexor reflex?
noxious stimulus causes a limb to flex
What is the pathway for the flexor reflex?
contraction of flexor muscles via excitatory interneurones and relaxation of extensor muscles via excitatory and inhibitory interneurones
What is the crossed extensor reflex?
activation of extensors and inhibition of flexors on the opposite side from the side affected by noxious stimuli
What is the purpose of the crossed extensor reflex?
To compensate for the extra load imposed by limb withdrawal
What special feature do excitatory interneurons have?
pacemaker activity
What is the pathway for the pacemaker activity of interneurons?
membrane is depolarised (NMDA receptors activated by glutamate)–Na and Ca flow into cell through NMDA–Ca activated K channels–K flows out cell–membrane hyperpolarises–Ca stops flowing into cell–K channels close–membrane depolares and the cycle repeats
What structures are responsible for high level strategy?
neocortical association areas and the basal ganglia
what structures are reponsible for middle level tactics?
motor cortex and cerebelum
What structures are responsible for low level execution?
brain stem and spinal cord
Where are the cell bodies of the rubrospinal tract located?
red nucleus
What is the function of the vetsibulospinal tract?
excites anti-gravity muscles and controls neck and back muscles for posture/balance
