Spinal Reflexes Flashcards
What is the difference between divergence and convergence in terms of interneurons?
convergence: lots of input to a single neuron
divergence: info from a single neuron goes to lot s of different neurons
What do group Ia inhibitory interneurons do?
reciprocal inhibition: as one group contracts, the opposing groups relax. Part of the stretch reflex that allows for the speed and efficiency of voluntary movement.
What happens with inhibition to the group Ia inhibitory interneurons?
descending inhibition of Ia interneurons allows for co-contracting of opposing muscles, which is important for joint stabilization.
What innervates Renshaw cells?
lower motor collaterals
What do renshaw cells inhibit? What is the process called?
inhibit signals fot homonymous and synergist motor units (aka “recurrent inhibition”). This forms a kind of negative feedback.
Also inhibit Ia inhibitory neurons to disinhibit antagonist motor units
From where do renshaw cells get input? What neurotransmitter do Renshaw cells secrete?
from descending pathways
Renshaw cells use glycine
What happens if you block Renshaw cell inhibition, and what is an example where this happens?
you get tetanus like response
seen in some rat poisons (strychnine)
From where do group Ib inhibitory interneurons get input?
from golgi tendon, from joint receptors from cunateous receptors, and from descending excitatory and inhibitory signals.
What do group IB inhibitory interneurons do?
inhibit homonymous and synergist motor neurons and give negative freedback for muscle tension regulation
In addition to influencing Ib inhibitory interneurons, what do Ib afferents do?
activate antagonist mor neurons via excitatory interneurons
What is the purpose of grou Ib inhibitory interneuron action?
integration of touch and movement to adjust movement when you reach out and come in contact with something
What is flexion withdrawal?
coordinated firing of excitatory and inhibitory interneurons that allows you to withdraw from noxious stimuli. the response is proportional to the stimulus intensity
What is What is crossed extension reflex?
the is the reflex that has to happen in coordination with flexion withdrawal in response to noxious stimuli in the lower extremities. these interneurons activate opposite reflexes in the contralateral limb to maintain balance.
What are long spinal reflexes?
change in upper limb position in response to lower limb stimuli. important for balance
What are central pattern organizers?
walking patterns generated within the spinal cord in cats (means that cats with cut cords can still “walk” on a treadmill). This is seen in human infants too when they are held upon a flat surface- but these patterns disappear after infancy because supraspinal processing is needed for bipedal movement.
