Evoked Reflexes Flashcards
mono synapse
disynapse
poly synapse
convergent pathway
Divergent pathway
Feedback excitation and inhibition
Circle and Triangle meaning
why can’t there by a divergent pathway with excitation and inhibiton
one interneuron to muscle
2 inter or 3 is poly
convergent comes from many neurons into 1
divergent comes from 1 to many
excitation means the more a neuron fires the more it increases its own firing rate
inhibition means the more a neuron fires the more it inhibits its own firing rate
triangle is excitatory, circle is inhibit
because neurons can only send out one EPSP of IPSP
monosynaptic arc
disynaptic arc
polysynaptic arc
one sensory to one inter then to muscle from motor
one sensory, two inter to motor
two sensory, to two different inter
one sensory to more than 2 inter
anatomy of a reflex
what happens the stronger a stimulus is
tendon measures a stretch
sends stimulus via sensory neuron to motor neuron
then alpha has an EMG response and makes muscle contract
stronger the stimulus the more action potentials are fired
Muscle stretch reflex
antagonistic muscles
MAKE SURE TO KNOW IF FLEXOR OR EXTENSOR IS BEING INHIBITED OF EXCITED
Hammer tap stretches tendon, stretches muscle spindles in leg extensor muscle
Sensory neuron excites motor neurons in spinal cord
interneuron excites extensor muscle
interneuron inhibits motor neurons to flexor
MN conduct action potential to extensor fibres causing contraction
Flexor muscles relax as MN has been inhibited
what happens when Im holding a coffee cup, and someone pours me a coffee
synergist muscle
extra weight added and spindle measures stretch
sends info to motor neuron via sensory
excites the bicep and brachialis(syngergist), which helps in the contraction
inhibits tricep so arm can get to 90 degrees
muscle stretch reflex
what does a single muscle spindle connect to
muscle spindle measures a stretch
sensory neuron sends info to spinal cord and to alpha MN, go to muscle to get it to contract
sensory connect to many interneurons and neuron pool connects to a large number of muscle spindles
what is faciliatory tonic excitatory input
could be another excitatory sensory input, cutaneous, or corticospinal tracts
there is the same stimulation of the muscle spindles, but extra stimulus is added for action potentials to reach threshold
there is tendon stretch but not enough, extra stimuli from cutaneous or corticospinal synapse onto the same Alpha MN and spindle does
cutaneous withdrawal
sensory steering
how does limb move based on where stimulus is
walk thru the steps
when skin is stimulated by pain
cutaneous withdrawal reflexes make sure the right muscles are activated to rapidly move limb away from pain stimuli
rapid steering mechanism away from pain, sensory steering
based on where stimulus is, the limb will move according to how to get away, activating dif muscles
Nociceptor reads pain, proprioception using GTO and spindles, tell the brain where the muscle is, and therefore how we must move to get away from pain
Flexion cross extension
Babinski Sign
do you want a positive sign
you step on a nail
ensures you retract the injured leg away from stimuli, and compensate by pressing down harder on the other legs and transferring body weight over
increase the motor drive to the other side
press down on plantar surface of the foot, and there is movement of the foot muscles, dorsiflexion of the big toe
abnormal for adults but normal for young children
shows a tumor, ALS, spinal cord injury, etc
no postive means bad
Activation of GTO during max muscle contraction
whats the inhibiton called
GTO measure active force production of the muscles and more action potentials the more force we produce
activation of GTO results in a protective reflex to shut down the muscle to prevent injury
AUTOGENIC INHIBITION reflex results in the inhibition of the muscle when output gets dangerously high
synapses onto an inhibitory interneuron and DECREASES FORCE IN FLEXOR AND ACTUALLY INCREASES FORCE ON EXTENSOR TO TAKE FORCE OFF
renshaw cell
inhibition name
NEGATIVE FEEDBACK LOOP
RECURRENT INHIBITION
A special type of inhibitory neuron, activated by a small collateral branch of an MN, that inhibits the MN and MNs that activated it
manages upper firing rate on alpha motor neurons, reduces the amount of force output in a muscle
descending outputs can also modulate renshaw cells
*Note that descending inputs can modulate the Renshaw Cells as well, which has the effect of setting the upper-limit on motor neuron firing rates (think of the ”limiter/ restrictor” on your car which kicks-in at around 160-180 km/h…).
Final common pathway
Motor neurons integrate inputs from a vast array of synaptic inputs, and if action potential
threshold is reached, they fire and contract muscle fibres. This is why they are called the FINAL
COMMON PATH, as all of these inputs go through the motor neuron to produce movement
all neurons have a lot of inputs, aMN get input from everywhere, many sensory organs affect firing rate of aMNs
