Somatosensory/Latency reflexes

Question 1

what is a converging pathway

Answer 1

large source population down to a small target population

Question 2

what is a diverging pathway

Answer 2

one source that expands out ot many targets
(ex: single muscle spindle to many MNs)

Question 3

how many NTs does a neuron contain

Answer 3

only 1
- can only be inhibitory OR excitatory

Question 4

what are the 4 steps of a basic reflex arc

Answer 4

1. AP from receptor in the skin/muscle
2. sensory neuron leads to the spinal cord
3. connects to one or more interneuronrs in the spinal cord
4. connects to MN that connects to the muscle

Question 5

what is a monosynaptic reflex

Answer 5

only one synapse (one interneuron)

Question 6

what is a disynaptic reflex

Answer 6

2 synapses (2 interneurons)

Question 7

what is a polysynaptic reflex

Answer 7

more than 2 synapses (mroe than 2 interneurons)
(can be set up many different ways)

Question 8

what is an example of the muscle stretch reflex

Answer 8

unexpectedly filling cup while hoding it
- increased load stretches bicep which increases muscle spindle firing before returning to baseline

Question 9

what is faciliatory tonic excitatory input

Answer 9

from cutaneous receptors or the brain
- same stimulation of muscle spindles would now be enough to cross threshold for APs
- makes reflexes more sensitive

Question 10

what are the two components of a short latency response (SLR)

Answer 10

phasic
static

Question 11

what is the phasic component of the SLR

Answer 11

transient/dynamic/velocity response
- is the difference between the peak in firing and the amount of firing during the stretch hold

Question 12

what 2 types of fibres are used in the 2 components of SLRs

Answer 12

phasic = bag type
static = chain type

Question 13

what is the static component of the SLR

Answer 13

difference in firing between rest and stretch hold
- offset due to new joint angle

Question 14

what are the equivalents of the SLR, LLR, and voluntary epoch

Answer 14

SLR = M1
LLR = M2/M3
voluntary epoch = V

Question 15

what are the inputs and processing areas for M1

Answer 15

spinal input
spinal processing

Question 16

what are the inputs and processing areas for M2/M3

Answer 16

cutaneous, propiroceptive + spinal inputs
processed in the brain (transcortical pathway)

Question 17

where is M1 reflex located

Answer 17

confined to spinal cord and PNS

Question 18

which reflex(es) do neurological disorders affect

Answer 18

M2/M3
- doesn’t affect M1 because everything occurs at the level of the spinal cord

Question 19

what type of pathways are used in withdrawal reflexes

Answer 19

divergent pathways
- cutaneous afferents onto multiple interneurons and aMNs

Question 20

what does klippel feil syndrome cause

Answer 20

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)

Question 21

what is a cutaneous withdrawal reflex

Answer 21

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

Question 22

what occurs during plantar vibration reflexes

Answer 22

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

Question 23

what lean occurs during certain vibration positions
(balls of the feet, heels, left and right sides)

Answer 23

balls of the feet = lean backward
heels = lean forward
left side = lean right
right side = lean left

Question 24

how is grip controlled in the hand

Answer 24

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

Question 25

what is the GTO autogenic inhibition reflex

Answer 25

activation of GTOs to shut down muscle under extreme force to protect tendons

Question 26

how is force ouput controlled

Answer 26

inhibiton from renshaw cells occurs at the same time as excitation
- inhibition just occurs at a lower rate than excitation