Video Transcript
Which of the following is a
response brought about by the parasympathetic nervous system? (A) An increase in blood
glucose. (B) A decrease in the secretion of
digestive enzymes. (C) A decrease in heart rate. (D) The dilation of pupils.
This question is asking us to
recall the functions of the parasympathetic nervous system. To answer this question, let’s
review what we know about the parasympathetic nervous system, which is one
subdivision of the autonomic nervous system.
The autonomic nervous system is a
subdivision of the motor division of the peripheral nervous system. The autonomic nervous system, which
controls all of the involuntary, subconscious motor functions, is subdivided into
the parasympathetic and sympathetic nervous systems. These two systems work in
opposition to one another to maintain the homeostatic balance of the body.
The sympathetic nervous system
takes over in times of stress when the body is preparing for action. So, the actions of the sympathetic
nervous system are often called the “fight-or-flight” responses. This highlights that when the goal
of the nervous response is to increase activity, the sympathetic nervous system is
activated. The range of responses that the
sympathetic nervous system controls includes actions such as increased heart rate,
decreased digestive activity, and dilation of the pupils.
The effects of the parasympathetic
nervous system are opposite that of the sympathetic nervous system and occur during
times of rest, relaxation, and feeding. So, the responses of the
parasympathetic nervous system are often called the “rest-and-digest” responses. This means that if the goal of the
nervous response is to decrease activity, the parasympathetic nervous system is
activated. The range of responses that the
parasympathetic nervous system control include actions such as decreased heart rate,
decreased blood sugar as liver cells take in glucose for storage, increased
digestive activity, and constriction of the pupils.
So, in reviewing the given answer
choices, we can eliminate any answer that is a response brought about by the need to
fight or take flight. This includes an increase in blood
glucose that would increase the energy available throughout the body. This would also include a decrease
in the production of digestive enzymes. And this includes the dilation of
pupils to ensure that there’s enough light entering the retina to clearly escape or
prepare for combat.
With this information, we are ready
to answer our question. A response brought about by the
parasympathetic nervous system is a decrease in heart rate.
