What is sensory adaptation
versus sensory amplification? So let's go into
adaptation first. So sensory adaptation
is change over time and the responsiveness
of the sensory receptor to a constant stimulus. And what this basically
is, is downregulation of a sensory receptor
somewhere on your body. So for example, if we
were to take our hand and place it on a table. So the hand is
placed on the table. As soon as the hand
touches the table, there are a whole bunch
of pressure receptors throughout your
fingers, in your palm. And they all experience
a change in pressure. And these pressure
receptors all simultaneously send a signal to the brain. After a few seconds of your
hand being placed on the table, the pressure receptors
are no longer firing. And in fact, you can even
forget that your hand is touching the table. So this occurs
because of adaptation. Another way we can
think of this is if we draw a pressure
receptor here. So this pressure
receptor is in our hand. This is the cell body,
the axon over here, and the axon terminal. As soon as the hand
rests on the table, there is pressure from the
weight of your hand touching the table, there's pressure. And this causes the cell to
fire in action potential. And this action potential
reaches the brain. Over a period of
time, however, as soon as your hand is just
resting on the table, there's no longer any
change in pressure. So this cell is no longer
sending a signal to the brain. And in fact, if you started
to press your hand down on the table, then
all of a sudden there would be again
a change in pressure. But then if you hold your
hand pressed on the table, then there's no longer
any change in pressure. And basically this is in a
nutshell what adaptation is. Adaptation is different
cells in your body responding to a change in a stimulus. If the stimulus is
no longer changing, then there's no
longer any information that's being sent to the brain. In contrast, amplification
is an upregulation. So upregulation of some sort
of stimulus in the environment. So for example, if we
take a ray of light-- and in previous videos,
we talked about vision and how a ray of
light is converted into an electrical impulse
that is sent to your brain. So the ray of light hits a
photoreceptor in your eye. And it actually triggers
a cascade of events. So for example, we can say that
if it will hit one molecule, and that molecule can
activate two molecules. And then those two molecules
can each activate two and so on. So eventually, what
happens is one ray of light can actually cause
a cell to fire. And when this cell fires
an action potential, it can actually be-- it might
be connected to maybe two cells. And these two cells then
also fire an action potential to two more. And so on and so forth. And by the time the signal
that this cell started reaches the brain,
it's been amplified. And so this is basically
amplification in a nutshell. And adaptation is important,
because if the cell is overexcited-- If any
cell is excited too much, it can actually be
harmful to the cell. And it can actually die. So it's really important
to have this adaptation. So for example, if this
was a pain receptor instead of a pressure receptor, and
if there is too much of a pain signal-- so for
example, one molecule that can actually cause pain
receptors to be activated is capsaicin. And we spoke about
this in another video. So if there's too much
capsaicin, for example, it can actually cause
the cell to die. And so that's why it's important
to downregulate a cell. It's important to adapt
to any type of stimulus in the environment, in
order for the cell both not to die, and then
also for your brain to not be overwhelmed
with information.