Now let’s take a closer look
at some of the specific reflexes.
The first reflex is going
to be the stretch reflex.
This causes contraction of a
muscle that has been stretched.
The stretch reflex is going
to try to control muscle length.
Usually a doctor test this reflex using
the hammer, the little rubber hammer
and he'll hit you on
the tendon on the knee.
Hitting the tendon causes that
muscle or that tendon to stretch
and therefore stimulates a sensory
receptor in the muscle spindle of the knee
From there, the sensory neuron is excited
and sends a message to the spinal cord.
So from the spinal cord, the sensory neuron
is going to synapse with the motor neuron.
The stretch reflex is a
monosynaptic reflex arc
So the sensory neuron directly
synapses with the motor neuron
and that motor neuron is going
to send an impulse to the effector
which is the muscle and
that muscle will contract.
At the same time, there is an inhibitory
interneuron in the spinal cord as well.
When this interneuron is going
to then send a inhibitory signal
to the antagonistic muscle
inhibiting that muscle so that it relaxes.
Thus, the muscle on the top, is going to contract
and the muscle on the back is going to relax.
This causes you to kick your foot up.