Somatosensory/Latency reflexes Flashcards
what is a converging pathway
large source population down to a small target population
what is a diverging pathway
one source that expands out ot many targets
(ex: single muscle spindle to many MNs)
how many NTs does a neuron contain
only 1
- can only be inhibitory OR excitatory
what are the 4 steps of a basic reflex arc
- AP from receptor in the skin/muscle
- sensory neuron leads to the spinal cord
- connects to one or more interneuronrs in the spinal cord
- connects to MN that connects to the muscle
what is a monosynaptic reflex
only one synapse (one interneuron)
what is a disynaptic reflex
2 synapses (2 interneurons)
what is a polysynaptic reflex
more than 2 synapses (mroe than 2 interneurons)
(can be set up many different ways)
what is an example of the muscle stretch reflex
unexpectedly filling cup while hoding it
- increased load stretches bicep which increases muscle spindle firing before returning to baseline
what is faciliatory tonic excitatory input
from cutaneous receptors or the brain
- same stimulation of muscle spindles would now be enough to cross threshold for APs
- makes reflexes more sensitive
what are the two components of a short latency response (SLR)
phasic
static
what is the phasic component of the SLR
transient/dynamic/velocity response
- is the difference between the peak in firing and the amount of firing during the stretch hold
what 2 types of fibres are used in the 2 components of SLRs
phasic = bag type
static = chain type
what is the static component of the SLR
difference in firing between rest and stretch hold
- offset due to new joint angle
what are the equivalents of the SLR, LLR, and voluntary epoch
SLR = M1
LLR = M2/M3
voluntary epoch = V
what are the inputs and processing areas for M1
spinal input
spinal processing
what are the inputs and processing areas for M2/M3
cutaneous, propiroceptive + spinal inputs
processed in the brain (transcortical pathway)
where is M1 reflex located
confined to spinal cord and PNS
which reflex(es) do neurological disorders affect
M2/M3
- doesn’t affect M1 because everything occurs at the level of the spinal cord
what type of pathways are used in withdrawal reflexes
divergent pathways
- cutaneous afferents onto multiple interneurons and aMNs
what does klippel feil syndrome cause
bilateral innervation - showing reflex response on both sides of the body
(regular response on same side and M2/M3 on the opposite side as well)
what is a cutaneous withdrawal reflex
when the skin is stimulated by a sudden painful event on the skin’s surface or more subtle forms of stimulation (stepping on tree root, low intensity electrical current)
- appropriate muscles are activated or inhibited to adaptively and rapidly withdraw the limb
what occurs during plantar vibration reflexes
vibration pattern applied to the bottom of the foot
- causes the standing person to reflexively start leaning
- gives sensation of more pressure on that area of the foot so they reflexively move away from it
what lean occurs during certain vibration positions
(balls of the feet, heels, left and right sides)
balls of the feet = lean backward
heels = lean forward
left side = lean right
right side = lean left
how is grip controlled in the hand
RA1 responds to different surfaces
- slippery material evoke greater responses from RA1
- as vibration increases, the more brain reads it as slippage so grip force increases
what is the GTO autogenic inhibition reflex
activation of GTOs to shut down muscle under extreme force to protect tendons
how is force ouput controlled
inhibiton from renshaw cells occurs at the same time as excitation
- inhibition just occurs at a lower rate than excitation
