Video Transcript
Baroreceptors are found in the
walls of the carotid arteries and the aorta. They detect changes in blood
pressure and regulate the heart rate accordingly. The flowchart provided shows a
basic outline of how this could work. Would this response be initiated by
the sympathetic or the parasympathetic nervous system? (A) Parasympathetic, (B)
sympathetic.
To answer this question, we need to
recall the difference in the functions of the sympathetic and parasympathetic
nervous systems. Then we’ll apply this knowledge to
how these systems would affect the function of the heart.
First, let’s recall that the
sympathetic and parasympathetic nervous systems are the two subdivisions of the
autonomic nervous system whose main goal is to regulate all of the involuntary and
subconscious motor functions of the body, such as the regulation of our
heartbeat. The sympathetic and parasympathetic
nervous systems are described as being antagonistic as they generally cause opposite
responses. This energetic balancing act helps
to keep the body in a state of homeostatic balance.
Now, let’s take a closer look at
the activities of each of these systems to get a better understanding of how their
functions will impact the sensory signals detected by the baroreceptors found at the
walls of carotid arteries and the aorta.
The sympathetic nervous system is
responsible for preparing the body for action. So its responses are commonly
called the fight-or-flight responses. This means that if the goal of the
nervous response is to increase activity, it involves the sympathetic nervous
system. In contrast, the parasympathetic
nervous system is responsible for the body’s rest-and-digest response, which occurs
when the body is relaxed, resting, or feeding. This means that if the goal of the
nervous response is to decrease activity, it involves the parasympathetic nervous
system.
Now that we’ve recalled that the
sympathetic nervous system works to increase activity, whereas the parasympathetic
nervous system works to decrease activity, we can take another look at the
flowchart. In the flowchart, we see that the
baroreceptors detect an increase in activity and therefore blood pressure. To keep the body in equilibrium,
the brain responds by sending signals to the sinoatrial valve to decrease the heart
rate. So the response to the baroreceptor
signal results in a decrease in activity, which we’ve just recalled is response
controlled by the parasympathetic nervous system.
Now that we have this information,
we can answer the question. The response outlined in the
flowchart would be initiated by the parasympathetic nervous system.
