Video Transcript
Which of the following shows the
correct process of a reflex arc?
This question is asking us to
review the answer choices and to pick the one where the steps of the reflex arc are
in the correct order. In order to answer this question,
we’ll look at an example reflex and map out its reflex arc. Then, we’ll be able to easily
choose the correct order. But what is a reflex? A reflex can be defined as an
automatic response to a stimulus that occurs without the need for conscious
thought. Reflexes serve an adaptive purpose,
usually to prevent injury or as a response to danger.
An example of one such reflexe is
called your corneal reflex. Your corneal reflex occurs when a
foreign object, such as some dust, comes in contact with the surface of your eye,
causing you to blink. The steps that outlined the
mechanism of a reflex is known as a reflex arc. Let’s take a closer look at the
reflex arc for your corneal reflex.
First, there’s the dust touching
the surface of your eye. This is called the stimulus, or the
change in the environment, that triggers the reflexive action. Next, the foreign object is
detected by special sensory cells on the surface of your eye. In the reflex arc, these are known
as the receptor. The receptor triggers a sensory
neuron, which senses the change and carries a signal to your central nervous system,
where it’s passed onto a relay neuron which, in turn, passes or relays the
information to a motor neuron.
The motor neuron’s job is to cause
motion. It does this by activating the
muscles in your eyelids, which are the effector in this relay arc. The effector is the part of your
body that causes the response to the stimulus. Finally, your eyelids come
together, causing you to blink. This is the last step in the reflex
arc, and it’s called the response. Now, we’re able to choose the
correct answer choice. The correct process of a reflex arc
is stimulus, receptor, sensory neuron, relay neuron, motor neuron, effector,
response.
