Hi, this is IAyda Basgul Martin . Welcome to my channel. Today, I will discuss with
you human anatomy and physiology of the reflex arc. If you want to watch more
videos, please feel free to click the subscribe button below at the end of
this video. In this slide, I put the getaway arch of
San Luis a picture too to point out the reflex arc and arch are not the same
things but it's an easy and common mistake between the students sometimes
one letter can change the meaning of the words yeah let's start talking about the
reflex arc at the end of this video you should able to define what is reflex and
what is reflex arc and describe the component of reflex arc in orderly
manner and identify these components on a policing optic reflex arc model. Reflex
is an immediate and subconscious reaction to a harmful stimulus. Reflex
arc and neural pathway that controls our reflexes. According to complexity, response,
development and processing side, there are different classifications. We will talk
here the polysynaptic and somatic reflexes
mostly. According to the complexity and reflex and reflex arc can
be defined as a monosynaptic or stretch and secondly polysynaptic curvature on
monosynaptic that means there's only one synapse. Polysynaptic, that means there is
more than one synapse in this reflex arc. Monosynaptic reflexes if we need to
give example it's deep tendon reflexes that commonly used in practice like
patellar reflex or knee jerk reflexes are good examples. Polysynaptic reflex arc is
a withdrawal reflexes when you put your hand on a hot surface
by accident, you immediately take your hands off through the polysynaptic reflex
arc. with withdrawal reflex. According to the response, either somatic that means
they are associated with skeletal muscle or autonomic that means they are
associated with internal organs. Without stimulus, there would be no reflex so you need
to have a stimulus and you need to able to receive that stimulus. So, first step
in the reflex arc is a receptor or a receptor organ or sensory organ. And after
the message taken, it has to be traveled to the central nervous system and this
done by sensory neuron or afferent neuron. The spinal cord is the
control center. In the spinal cord, we have an interneuron or intermediary
neuron or association neuron, they all the same thing and this neuron allows
transmitting the information from sensory neuron to motor neuron. Motor
neuron has another name efferent neuron and brings the order to related effector
organ. The effector organ does give the response. Let's repeat it what is the
order of the reflex arc and compare with or show and those are components on
the reflex arc on the polysynaptic reflex arc model. First sensory organ.Think about it,
if there is a hard surface and you put your hand on, your skin is the first as
sensory organ which it labeled with the number one. And the information
carried to the spinal cord through the number two label with the number two is
sensory neuron or afferent neuron and inter neuron the number third in
an intermediary or interneuron and labelled with three and green color
coded. The motor neuron is a red color coded and numbered or labelled with
number four. Effector organ is number five as you see it. When we have a danger,
we have to give a quick response, this is a subconscious involuntary response
involuntary that means it's not under the brain's conscious
control, however and then when the response is given and and there is an
Information center brain so if there is any further things to do the brain can
have to do the process or you can create a memory so you know that oven might be hot, do
not touch it, when it's hot. The reflexes are the most
objective part of the neurologic examination and they are commonly used
in practice to determine if there is a damage in the nervous system or not.If
there is what is the level of this damage and I list it for you to some
common reflexes that we use in practice often. Stretch reflexes are deep
tendon reflexes as we mentioned it. Superficial reflexes like gag reflex,
corneal or plantar reflex are used as well.
I wrote next to the gag reflex and cranial nerves because they are cranial
reflexes and number nine with a Roman number is the sensory neuron for gag
reflex and and cranial nerve ten is the motor neuron for gag reflex.
Visceral autonomic reflexes, good example is a pupillary light reflex which is
cranial nerve two or optic nerve is the sensory and cranial nerve three, ocular motor is the
motor neuron for visceral autonomic reflexes.
Babinski reflex is commonly used plantar reflex. When you scratch along
the lateral aspect of the sole of the foot with an object across the ball of
the foot toward great toe it caused extension of the great toe and fanning
of the other toes we call this Babinski positive. Babinski
positivity it's normal in the first six month of life but if it is still seen after
six months of life, it considered a pathological reflex and suggests the presence of an
upper motor lesion. Babinski reflex known even in the 15th century. You can see the
Botticelli's madonna, child and two angels art, it shows the
Babinski reflex is presented. I hope you learned the reflex
actions are involuntary and immediate and most effects are polysynaptic an
order of polysynoptic reflex arc first receptor or sensory organ, second
sensory neuron, third intermediary neuron ,fourth motor neurone and fifth effector.
The reflexes are the most objective part of neurologic examination and Babinski
reflex positivity might be suggestion an upper motor neuron damage after six
months of life. Can you test your knowledge? What is the number four stands
for?Yes, if you said the motor neuron you are right and what is the number two
depicts and it is sensory neuron you are right, and number one is the sensory
organ and number five is effector organ and number three is the interneuron. If you
are struggling with any subject of human anatomy physiology, please feel free to
comment below on my video and I'll be happy to make a
video to clarify or help to ease your struggle. Thank you for stopping by! I
hope you learned and enjoyed it. Have a good day!