Somatosensory Evoked Reflexes

Question 1

Disynaptic

Answer 1

two synapses btwn point A and B

Question 2

Convergent pathway

Answer 2

many to one (sensory)

Question 3

Divergent pathway

Answer 3

one to many (motor response)

Question 4

What does a triangle mean in a neuron diagram?

Answer 4

excitatory input

Question 5

What does a circle mean in a neuron diagram?

Answer 5

inhibitory input

Question 6

Feedback excitation

Answer 6

positive feedback loop (continues firing)

Question 7

Feedback inhibition

Answer 7

negative feedback loop (increased firing turns itself/something else off)

Question 8

Can a divergent neuron have both excitatory and inhibitory synapses?

Answer 8

No, can only have one type per neuron

Question 9

What is reciprocal inhibition?

Answer 9

Contraction of agonist, inhibition of antagonist (together for smooth movement)

Question 10

In the knee jerk response what is the initial stimulant?

Answer 10

Hammer tap stretches tendon (in turn stretched sensory receptors in leg extensor- quadriceps)

Question 11

Explain the three synapses present

Answer 11

1) sensory neuron excites motor neuron (extensor muscle) in spinal cord
2) sensory neuron excites interneuron
3) interneuron inhibits motor neuron (flexor muscle)

Question 12

Describe the response (in the muscles) of knee jerk tap

Answer 12

-extensor (quads) contract
-flexor (hamstrings) relax b/c inhibited

Question 13

What is the final response of knee jerk?

Answer 13

Leg extends

Question 14

synergist

Answer 14

supports direction of muscle agonist

Question 15

Faciliatory tonic excitatory input

Answer 15

summation of inputs enough to cross threshold for action potentials

Question 16

What does activating the gastrocnemius (heel stimulus) do?

Answer 16

-push toes down
-lift heels up
-plantarflexion

Question 17

What does activating tibialis anterior (toe stimulus) do?

Answer 17

-forces toes upward
-push heel down
-dorsiflexion

Question 18

sensory steering

Answer 18

rapid reflex response to move away from harmful stimulus

Question 19

cutaneous withdrawal reflex

Answer 19

utilizes sensory steering to move away from harmful stimulus

Question 20

Flexion-crossed-extension

Answer 20

reflex circuitry that acts to compensate for reflex movement (ie. shifting weight to alternate foot)

Question 21

Another name for plantar reflex?

Answer 21

Babinski’s sign

Question 22

Explain the results of plantar reflex test

Answer 22

1) toes curl (normal)
2) toes flex (potential spinal injury, stroke, brain injury)

Question 23

Autogenic inhibition

Answer 23

inhibition of the muscle when its force output becomes dangerously high (detected by GTO’s)

Question 24

Renshaw cell

Answer 24

inhibitory interneuron (results in negative feedback loop = recurrent inhibition)

Question 25

Which cell works as an “upper limit” on motor neuron firing rates?

Answer 25

Renshaw cell

Question 26

How is the final common path of a motor neuron reached?

Answer 26

integrated inputs from various areas (if threshold reached - fire!)